Re: [EXT] Re: [PATCH v9 1/9] hw/vfio/common: Remove error print on mmio region translation by viommu
Hi Bharat,
On 5/5/20 12:18 PM, Bharat Bhushan wrote:
> Hi Eric,
>
> On Tue, May 5, 2020 at 3:16 PM Bharat Bhushan wrote:
>>
>> hi Eric,
>>
>> On Tue, May 5, 2020 at 3:00 PM Auger Eric wrote:
>>>
>>> Hi Bharat,
>>>
>>> On 5/5/20 11:25 AM, Bharat Bhushan wrote:
>>>> Hi Eric,
>>>>
>>>> On Fri, Apr 24, 2020 at 7:47 PM Auger Eric wrote:
>>>>>
>>>>> Hi Bharat,
>>>>>
>>>>> On 4/2/20 11:01 AM, Bharat Bhushan wrote:
>>>>>> Hi Eric/Alex,
>>>>>>
>>>>>>> -Original Message-
>>>>>>> From: Alex Williamson
>>>>>>> Sent: Thursday, March 26, 2020 11:23 PM
>>>>>>> To: Auger Eric
>>>>>>> Cc: Bharat Bhushan ; peter.mayd...@linaro.org;
>>>>>>> pet...@redhat.com; eric.auger....@gmail.com; kevin.t...@intel.com;
>>>>>>> m...@redhat.com; Tomasz Nowicki [C] ;
>>>>>>> drjo...@redhat.com; linuc.dec...@gmail.com; qemu-devel@nongnu.org; qemu-
>>>>>>> a...@nongnu.org; bharatb.li...@gmail.com; jean-phili...@linaro.org;
>>>>>>> yang.zh...@intel.com; David Gibson
>>>>>>> Subject: [EXT] Re: [PATCH v9 1/9] hw/vfio/common: Remove error print on
>>>>>>> mmio
>>>>>>> region translation by viommu
>>>>>>>
>>>>>>> External Email
>>>>>>>
>>>>>>> --
>>>>>>> On Thu, 26 Mar 2020 18:35:48 +0100
>>>>>>> Auger Eric wrote:
>>>>>>>
>>>>>>>> Hi Alex,
>>>>>>>>
>>>>>>>> On 3/24/20 12:08 AM, Alex Williamson wrote:
>>>>>>>>> [Cc +dwg who originated this warning]
>>>>>>>>>
>>>>>>>>> On Mon, 23 Mar 2020 14:16:09 +0530
>>>>>>>>> Bharat Bhushan wrote:
>>>>>>>>>
>>>>>>>>>> On ARM, the MSI doorbell is translated by the virtual IOMMU.
>>>>>>>>>> As such address_space_translate() returns the MSI controller MMIO
>>>>>>>>>> region and we get an "iommu map to non memory area"
>>>>>>>>>> message. Let's remove this latter.
>>>>>>>>>>
>>>>>>>>>> Signed-off-by: Eric Auger
>>>>>>>>>> Signed-off-by: Bharat Bhushan
>>>>>>>>>> ---
>>>>>>>>>> hw/vfio/common.c | 2 --
>>>>>>>>>> 1 file changed, 2 deletions(-)
>>>>>>>>>>
>>>>>>>>>> diff --git a/hw/vfio/common.c b/hw/vfio/common.c index
>>>>>>>>>> 5ca11488d6..c586edf47a 100644
>>>>>>>>>> --- a/hw/vfio/common.c
>>>>>>>>>> +++ b/hw/vfio/common.c
>>>>>>>>>> @@ -426,8 +426,6 @@ static bool vfio_get_vaddr(IOMMUTLBEntry *iotlb,
>>>>>>> void **vaddr,
>>>>>>>>>> , , writable,
>>>>>>>>>> MEMTXATTRS_UNSPECIFIED);
>>>>>>>>>> if (!memory_region_is_ram(mr)) {
>>>>>>>>>> -error_report("iommu map to non memory area %"HWADDR_PRIx"",
>>>>>>>>>> - xlat);
>>>>>>>>>> return false;
>>>>>>>>>> }
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> I'm a bit confused here, I think we need more justification beyond
>>>>>>>>> "we hit this warning and we don't want to because it's ok in this
>>>>>>>>> one special case, therefore remove it". I assume the special case
>>>>>>>>> is that the device MSI address is managed via the SET_IRQS ioctl and
>>>>>>>>> therefore we won't actually get DMAs to this range.
>>>>>>>> Yes exactly. The guest creates a mapping between one giova and this
>>>>>>>> gpa (corresponding to the MSI controller doorbell) because MSIs are
>>>>>>>> map
Re: [EXT] Re: [PATCH v9 1/9] hw/vfio/common: Remove error print on mmio region translation by viommu
Hi Bharat,
On 5/5/20 12:18 PM, Bharat Bhushan wrote:
> Hi Eric,
>
> On Tue, May 5, 2020 at 3:16 PM Bharat Bhushan wrote:
>>
>> hi Eric,
>>
>> On Tue, May 5, 2020 at 3:00 PM Auger Eric wrote:
>>>
>>> Hi Bharat,
>>>
>>> On 5/5/20 11:25 AM, Bharat Bhushan wrote:
>>>> Hi Eric,
>>>>
>>>> On Fri, Apr 24, 2020 at 7:47 PM Auger Eric wrote:
>>>>>
>>>>> Hi Bharat,
>>>>>
>>>>> On 4/2/20 11:01 AM, Bharat Bhushan wrote:
>>>>>> Hi Eric/Alex,
>>>>>>
>>>>>>> -Original Message-
>>>>>>> From: Alex Williamson
>>>>>>> Sent: Thursday, March 26, 2020 11:23 PM
>>>>>>> To: Auger Eric
>>>>>>> Cc: Bharat Bhushan ; peter.mayd...@linaro.org;
>>>>>>> pet...@redhat.com; eric.auger....@gmail.com; kevin.t...@intel.com;
>>>>>>> m...@redhat.com; Tomasz Nowicki [C] ;
>>>>>>> drjo...@redhat.com; linuc.dec...@gmail.com; qemu-devel@nongnu.org; qemu-
>>>>>>> a...@nongnu.org; bharatb.li...@gmail.com; jean-phili...@linaro.org;
>>>>>>> yang.zh...@intel.com; David Gibson
>>>>>>> Subject: [EXT] Re: [PATCH v9 1/9] hw/vfio/common: Remove error print on
>>>>>>> mmio
>>>>>>> region translation by viommu
>>>>>>>
>>>>>>> External Email
>>>>>>>
>>>>>>> --
>>>>>>> On Thu, 26 Mar 2020 18:35:48 +0100
>>>>>>> Auger Eric wrote:
>>>>>>>
>>>>>>>> Hi Alex,
>>>>>>>>
>>>>>>>> On 3/24/20 12:08 AM, Alex Williamson wrote:
>>>>>>>>> [Cc +dwg who originated this warning]
>>>>>>>>>
>>>>>>>>> On Mon, 23 Mar 2020 14:16:09 +0530
>>>>>>>>> Bharat Bhushan wrote:
>>>>>>>>>
>>>>>>>>>> On ARM, the MSI doorbell is translated by the virtual IOMMU.
>>>>>>>>>> As such address_space_translate() returns the MSI controller MMIO
>>>>>>>>>> region and we get an "iommu map to non memory area"
>>>>>>>>>> message. Let's remove this latter.
>>>>>>>>>>
>>>>>>>>>> Signed-off-by: Eric Auger
>>>>>>>>>> Signed-off-by: Bharat Bhushan
>>>>>>>>>> ---
>>>>>>>>>> hw/vfio/common.c | 2 --
>>>>>>>>>> 1 file changed, 2 deletions(-)
>>>>>>>>>>
>>>>>>>>>> diff --git a/hw/vfio/common.c b/hw/vfio/common.c index
>>>>>>>>>> 5ca11488d6..c586edf47a 100644
>>>>>>>>>> --- a/hw/vfio/common.c
>>>>>>>>>> +++ b/hw/vfio/common.c
>>>>>>>>>> @@ -426,8 +426,6 @@ static bool vfio_get_vaddr(IOMMUTLBEntry *iotlb,
>>>>>>> void **vaddr,
>>>>>>>>>> , , writable,
>>>>>>>>>> MEMTXATTRS_UNSPECIFIED);
>>>>>>>>>> if (!memory_region_is_ram(mr)) {
>>>>>>>>>> -error_report("iommu map to non memory area %"HWADDR_PRIx"",
>>>>>>>>>> - xlat);
>>>>>>>>>> return false;
>>>>>>>>>> }
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> I'm a bit confused here, I think we need more justification beyond
>>>>>>>>> "we hit this warning and we don't want to because it's ok in this
>>>>>>>>> one special case, therefore remove it". I assume the special case
>>>>>>>>> is that the device MSI address is managed via the SET_IRQS ioctl and
>>>>>>>>> therefore we won't actually get DMAs to this range.
>>>>>>>> Yes exactly. The guest creates a mapping between one giova and this
>>>>>>>> gpa (corresponding to the MSI controller doorbell) because MSIs are
>>>>>>>> map
Re: [EXT] Re: [PATCH v9 1/9] hw/vfio/common: Remove error print on mmio region translation by viommu
Hi Eric,
On Tue, May 5, 2020 at 3:16 PM Bharat Bhushan wrote:
>
> hi Eric,
>
> On Tue, May 5, 2020 at 3:00 PM Auger Eric wrote:
> >
> > Hi Bharat,
> >
> > On 5/5/20 11:25 AM, Bharat Bhushan wrote:
> > > Hi Eric,
> > >
> > > On Fri, Apr 24, 2020 at 7:47 PM Auger Eric wrote:
> > >>
> > >> Hi Bharat,
> > >>
> > >> On 4/2/20 11:01 AM, Bharat Bhushan wrote:
> > >>> Hi Eric/Alex,
> > >>>
> > >>>> -Original Message-
> > >>>> From: Alex Williamson
> > >>>> Sent: Thursday, March 26, 2020 11:23 PM
> > >>>> To: Auger Eric
> > >>>> Cc: Bharat Bhushan ; peter.mayd...@linaro.org;
> > >>>> pet...@redhat.com; eric.auger@gmail.com; kevin.t...@intel.com;
> > >>>> m...@redhat.com; Tomasz Nowicki [C] ;
> > >>>> drjo...@redhat.com; linuc.dec...@gmail.com; qemu-devel@nongnu.org;
> > >>>> qemu-
> > >>>> a...@nongnu.org; bharatb.li...@gmail.com; jean-phili...@linaro.org;
> > >>>> yang.zh...@intel.com; David Gibson
> > >>>> Subject: [EXT] Re: [PATCH v9 1/9] hw/vfio/common: Remove error print
> > >>>> on mmio
> > >>>> region translation by viommu
> > >>>>
> > >>>> External Email
> > >>>>
> > >>>> --
> > >>>> On Thu, 26 Mar 2020 18:35:48 +0100
> > >>>> Auger Eric wrote:
> > >>>>
> > >>>>> Hi Alex,
> > >>>>>
> > >>>>> On 3/24/20 12:08 AM, Alex Williamson wrote:
> > >>>>>> [Cc +dwg who originated this warning]
> > >>>>>>
> > >>>>>> On Mon, 23 Mar 2020 14:16:09 +0530
> > >>>>>> Bharat Bhushan wrote:
> > >>>>>>
> > >>>>>>> On ARM, the MSI doorbell is translated by the virtual IOMMU.
> > >>>>>>> As such address_space_translate() returns the MSI controller MMIO
> > >>>>>>> region and we get an "iommu map to non memory area"
> > >>>>>>> message. Let's remove this latter.
> > >>>>>>>
> > >>>>>>> Signed-off-by: Eric Auger
> > >>>>>>> Signed-off-by: Bharat Bhushan
> > >>>>>>> ---
> > >>>>>>> hw/vfio/common.c | 2 --
> > >>>>>>> 1 file changed, 2 deletions(-)
> > >>>>>>>
> > >>>>>>> diff --git a/hw/vfio/common.c b/hw/vfio/common.c index
> > >>>>>>> 5ca11488d6..c586edf47a 100644
> > >>>>>>> --- a/hw/vfio/common.c
> > >>>>>>> +++ b/hw/vfio/common.c
> > >>>>>>> @@ -426,8 +426,6 @@ static bool vfio_get_vaddr(IOMMUTLBEntry *iotlb,
> > >>>> void **vaddr,
> > >>>>>>> , , writable,
> > >>>>>>> MEMTXATTRS_UNSPECIFIED);
> > >>>>>>> if (!memory_region_is_ram(mr)) {
> > >>>>>>> -error_report("iommu map to non memory area %"HWADDR_PRIx"",
> > >>>>>>> - xlat);
> > >>>>>>> return false;
> > >>>>>>> }
> > >>>>>>>
> > >>>>>>
> > >>>>>> I'm a bit confused here, I think we need more justification beyond
> > >>>>>> "we hit this warning and we don't want to because it's ok in this
> > >>>>>> one special case, therefore remove it". I assume the special case
> > >>>>>> is that the device MSI address is managed via the SET_IRQS ioctl and
> > >>>>>> therefore we won't actually get DMAs to this range.
> > >>>>> Yes exactly. The guest creates a mapping between one giova and this
> > >>>>> gpa (corresponding to the MSI controller doorbell) because MSIs are
> > >>>>> mapped on ARM. But practically the physical device is programmed with
> > >>>>> an host chosen iova that maps onto the physical MSI controller's
> > >>>>> doorb
Re: [EXT] Re: [PATCH v9 1/9] hw/vfio/common: Remove error print on mmio region translation by viommu
hi Eric,
On Tue, May 5, 2020 at 3:00 PM Auger Eric wrote:
>
> Hi Bharat,
>
> On 5/5/20 11:25 AM, Bharat Bhushan wrote:
> > Hi Eric,
> >
> > On Fri, Apr 24, 2020 at 7:47 PM Auger Eric wrote:
> >>
> >> Hi Bharat,
> >>
> >> On 4/2/20 11:01 AM, Bharat Bhushan wrote:
> >>> Hi Eric/Alex,
> >>>
> >>>> -Original Message-
> >>>> From: Alex Williamson
> >>>> Sent: Thursday, March 26, 2020 11:23 PM
> >>>> To: Auger Eric
> >>>> Cc: Bharat Bhushan ; peter.mayd...@linaro.org;
> >>>> pet...@redhat.com; eric.auger@gmail.com; kevin.t...@intel.com;
> >>>> m...@redhat.com; Tomasz Nowicki [C] ;
> >>>> drjo...@redhat.com; linuc.dec...@gmail.com; qemu-devel@nongnu.org; qemu-
> >>>> a...@nongnu.org; bharatb.li...@gmail.com; jean-phili...@linaro.org;
> >>>> yang.zh...@intel.com; David Gibson
> >>>> Subject: [EXT] Re: [PATCH v9 1/9] hw/vfio/common: Remove error print on
> >>>> mmio
> >>>> region translation by viommu
> >>>>
> >>>> External Email
> >>>>
> >>>> --
> >>>> On Thu, 26 Mar 2020 18:35:48 +0100
> >>>> Auger Eric wrote:
> >>>>
> >>>>> Hi Alex,
> >>>>>
> >>>>> On 3/24/20 12:08 AM, Alex Williamson wrote:
> >>>>>> [Cc +dwg who originated this warning]
> >>>>>>
> >>>>>> On Mon, 23 Mar 2020 14:16:09 +0530
> >>>>>> Bharat Bhushan wrote:
> >>>>>>
> >>>>>>> On ARM, the MSI doorbell is translated by the virtual IOMMU.
> >>>>>>> As such address_space_translate() returns the MSI controller MMIO
> >>>>>>> region and we get an "iommu map to non memory area"
> >>>>>>> message. Let's remove this latter.
> >>>>>>>
> >>>>>>> Signed-off-by: Eric Auger
> >>>>>>> Signed-off-by: Bharat Bhushan
> >>>>>>> ---
> >>>>>>> hw/vfio/common.c | 2 --
> >>>>>>> 1 file changed, 2 deletions(-)
> >>>>>>>
> >>>>>>> diff --git a/hw/vfio/common.c b/hw/vfio/common.c index
> >>>>>>> 5ca11488d6..c586edf47a 100644
> >>>>>>> --- a/hw/vfio/common.c
> >>>>>>> +++ b/hw/vfio/common.c
> >>>>>>> @@ -426,8 +426,6 @@ static bool vfio_get_vaddr(IOMMUTLBEntry *iotlb,
> >>>> void **vaddr,
> >>>>>>> , , writable,
> >>>>>>> MEMTXATTRS_UNSPECIFIED);
> >>>>>>> if (!memory_region_is_ram(mr)) {
> >>>>>>> -error_report("iommu map to non memory area %"HWADDR_PRIx"",
> >>>>>>> - xlat);
> >>>>>>> return false;
> >>>>>>> }
> >>>>>>>
> >>>>>>
> >>>>>> I'm a bit confused here, I think we need more justification beyond
> >>>>>> "we hit this warning and we don't want to because it's ok in this
> >>>>>> one special case, therefore remove it". I assume the special case
> >>>>>> is that the device MSI address is managed via the SET_IRQS ioctl and
> >>>>>> therefore we won't actually get DMAs to this range.
> >>>>> Yes exactly. The guest creates a mapping between one giova and this
> >>>>> gpa (corresponding to the MSI controller doorbell) because MSIs are
> >>>>> mapped on ARM. But practically the physical device is programmed with
> >>>>> an host chosen iova that maps onto the physical MSI controller's
> >>>>> doorbell. so the device never performs DMA accesses to this range.
> >>>>>
> >>>>> But I imagine the case that
> >>>>>> was in mind when adding this warning was general peer-to-peer
> >>>>>> between and assigned and emulated device.
> >>>>> yes makes sense.
> >>>>>
> >>>>> Maybe there's an argument to be made
> >>>>>> that such a p2p mapping might
Re: [EXT] Re: [PATCH v9 1/9] hw/vfio/common: Remove error print on mmio region translation by viommu
Hi Bharat,
On 5/5/20 11:25 AM, Bharat Bhushan wrote:
> Hi Eric,
>
> On Fri, Apr 24, 2020 at 7:47 PM Auger Eric wrote:
>>
>> Hi Bharat,
>>
>> On 4/2/20 11:01 AM, Bharat Bhushan wrote:
>>> Hi Eric/Alex,
>>>
>>>> -Original Message-
>>>> From: Alex Williamson
>>>> Sent: Thursday, March 26, 2020 11:23 PM
>>>> To: Auger Eric
>>>> Cc: Bharat Bhushan ; peter.mayd...@linaro.org;
>>>> pet...@redhat.com; eric.auger@gmail.com; kevin.t...@intel.com;
>>>> m...@redhat.com; Tomasz Nowicki [C] ;
>>>> drjo...@redhat.com; linuc.dec...@gmail.com; qemu-devel@nongnu.org; qemu-
>>>> a...@nongnu.org; bharatb.li...@gmail.com; jean-phili...@linaro.org;
>>>> yang.zh...@intel.com; David Gibson
>>>> Subject: [EXT] Re: [PATCH v9 1/9] hw/vfio/common: Remove error print on
>>>> mmio
>>>> region translation by viommu
>>>>
>>>> External Email
>>>>
>>>> --
>>>> On Thu, 26 Mar 2020 18:35:48 +0100
>>>> Auger Eric wrote:
>>>>
>>>>> Hi Alex,
>>>>>
>>>>> On 3/24/20 12:08 AM, Alex Williamson wrote:
>>>>>> [Cc +dwg who originated this warning]
>>>>>>
>>>>>> On Mon, 23 Mar 2020 14:16:09 +0530
>>>>>> Bharat Bhushan wrote:
>>>>>>
>>>>>>> On ARM, the MSI doorbell is translated by the virtual IOMMU.
>>>>>>> As such address_space_translate() returns the MSI controller MMIO
>>>>>>> region and we get an "iommu map to non memory area"
>>>>>>> message. Let's remove this latter.
>>>>>>>
>>>>>>> Signed-off-by: Eric Auger
>>>>>>> Signed-off-by: Bharat Bhushan
>>>>>>> ---
>>>>>>> hw/vfio/common.c | 2 --
>>>>>>> 1 file changed, 2 deletions(-)
>>>>>>>
>>>>>>> diff --git a/hw/vfio/common.c b/hw/vfio/common.c index
>>>>>>> 5ca11488d6..c586edf47a 100644
>>>>>>> --- a/hw/vfio/common.c
>>>>>>> +++ b/hw/vfio/common.c
>>>>>>> @@ -426,8 +426,6 @@ static bool vfio_get_vaddr(IOMMUTLBEntry *iotlb,
>>>> void **vaddr,
>>>>>>> , , writable,
>>>>>>> MEMTXATTRS_UNSPECIFIED);
>>>>>>> if (!memory_region_is_ram(mr)) {
>>>>>>> -error_report("iommu map to non memory area %"HWADDR_PRIx"",
>>>>>>> - xlat);
>>>>>>> return false;
>>>>>>> }
>>>>>>>
>>>>>>
>>>>>> I'm a bit confused here, I think we need more justification beyond
>>>>>> "we hit this warning and we don't want to because it's ok in this
>>>>>> one special case, therefore remove it". I assume the special case
>>>>>> is that the device MSI address is managed via the SET_IRQS ioctl and
>>>>>> therefore we won't actually get DMAs to this range.
>>>>> Yes exactly. The guest creates a mapping between one giova and this
>>>>> gpa (corresponding to the MSI controller doorbell) because MSIs are
>>>>> mapped on ARM. But practically the physical device is programmed with
>>>>> an host chosen iova that maps onto the physical MSI controller's
>>>>> doorbell. so the device never performs DMA accesses to this range.
>>>>>
>>>>> But I imagine the case that
>>>>>> was in mind when adding this warning was general peer-to-peer
>>>>>> between and assigned and emulated device.
>>>>> yes makes sense.
>>>>>
>>>>> Maybe there's an argument to be made
>>>>>> that such a p2p mapping might also be used in a non-vIOMMU case. We
>>>>>> skip creating those mappings and drivers continue to work, maybe
>>>>>> because nobody attempts to do p2p DMA with the types of devices we
>>>>>> emulate, maybe because p2p DMA is not absolutely reliable on bare
>>>>>> metal and drivers test it before using it.
>>>>> MSI doorbells are mapped using the IOMMU_MMIO flag (dma-iommu.c
>>>>> iommu_dma_get_msi_page).
>>>>> One idea could be to pass that flag through the IOMMU Notifier
>>>>> mechanism into the iotlb->perm. Eventually when we get this in
>>>>> vfio_get_vaddr() we would not print the warning. Could that make sense?
>>>>
>>>> Yeah, if we can identify a valid case that doesn't need a warning, that's
>>>> fine by me.
>>>> Thanks,
>>>
>>> Let me know if I understood the proposal correctly:
>>>
>>> virtio-iommu driver in guest will make map (VIRTIO_IOMMU_T_MAP) with
>>> VIRTIO_IOMMU_MAP_F_MMIO flag for MSI mapping.
>>> In qemu, virtio-iommu device will set a new defined flag (say IOMMU_MMIO)
>>> in iotlb->perm in memory_region_notify_iommu(). vfio_get_vaddr() will check
>>> same flag and will not print the warning.>
>>> Is above correct?
>> Yes that's what I had in mind.
>
> In that case virtio-iommu driver in guest should not make map
> (VIRTIO_IOMMU_T_MAP) call as it known nothing to be mapped.
sorry I don't catch what you meant. Please can you elaborate?
Thanks
Eric
>
> Stay Safe
>
> Thanks
> -Bharat
>
>>
>> Thanks
>>
>> Eric
>>>
>>> Thanks
>>> -Bharat
>>>
>>>>
>>>> Alex
>>>
>>>
>>
>
Re: [EXT] Re: [PATCH v9 1/9] hw/vfio/common: Remove error print on mmio region translation by viommu
Hi Eric,
On Fri, Apr 24, 2020 at 7:47 PM Auger Eric wrote:
>
> Hi Bharat,
>
> On 4/2/20 11:01 AM, Bharat Bhushan wrote:
> > Hi Eric/Alex,
> >
> >> -Original Message-
> >> From: Alex Williamson
> >> Sent: Thursday, March 26, 2020 11:23 PM
> >> To: Auger Eric
> >> Cc: Bharat Bhushan ; peter.mayd...@linaro.org;
> >> pet...@redhat.com; eric.auger@gmail.com; kevin.t...@intel.com;
> >> m...@redhat.com; Tomasz Nowicki [C] ;
> >> drjo...@redhat.com; linuc.dec...@gmail.com; qemu-devel@nongnu.org; qemu-
> >> a...@nongnu.org; bharatb.li...@gmail.com; jean-phili...@linaro.org;
> >> yang.zh...@intel.com; David Gibson
> >> Subject: [EXT] Re: [PATCH v9 1/9] hw/vfio/common: Remove error print on
> >> mmio
> >> region translation by viommu
> >>
> >> External Email
> >>
> >> --
> >> On Thu, 26 Mar 2020 18:35:48 +0100
> >> Auger Eric wrote:
> >>
> >>> Hi Alex,
> >>>
> >>> On 3/24/20 12:08 AM, Alex Williamson wrote:
> >>>> [Cc +dwg who originated this warning]
> >>>>
> >>>> On Mon, 23 Mar 2020 14:16:09 +0530
> >>>> Bharat Bhushan wrote:
> >>>>
> >>>>> On ARM, the MSI doorbell is translated by the virtual IOMMU.
> >>>>> As such address_space_translate() returns the MSI controller MMIO
> >>>>> region and we get an "iommu map to non memory area"
> >>>>> message. Let's remove this latter.
> >>>>>
> >>>>> Signed-off-by: Eric Auger
> >>>>> Signed-off-by: Bharat Bhushan
> >>>>> ---
> >>>>> hw/vfio/common.c | 2 --
> >>>>> 1 file changed, 2 deletions(-)
> >>>>>
> >>>>> diff --git a/hw/vfio/common.c b/hw/vfio/common.c index
> >>>>> 5ca11488d6..c586edf47a 100644
> >>>>> --- a/hw/vfio/common.c
> >>>>> +++ b/hw/vfio/common.c
> >>>>> @@ -426,8 +426,6 @@ static bool vfio_get_vaddr(IOMMUTLBEntry *iotlb,
> >> void **vaddr,
> >>>>> , , writable,
> >>>>> MEMTXATTRS_UNSPECIFIED);
> >>>>> if (!memory_region_is_ram(mr)) {
> >>>>> -error_report("iommu map to non memory area %"HWADDR_PRIx"",
> >>>>> - xlat);
> >>>>> return false;
> >>>>> }
> >>>>>
> >>>>
> >>>> I'm a bit confused here, I think we need more justification beyond
> >>>> "we hit this warning and we don't want to because it's ok in this
> >>>> one special case, therefore remove it". I assume the special case
> >>>> is that the device MSI address is managed via the SET_IRQS ioctl and
> >>>> therefore we won't actually get DMAs to this range.
> >>> Yes exactly. The guest creates a mapping between one giova and this
> >>> gpa (corresponding to the MSI controller doorbell) because MSIs are
> >>> mapped on ARM. But practically the physical device is programmed with
> >>> an host chosen iova that maps onto the physical MSI controller's
> >>> doorbell. so the device never performs DMA accesses to this range.
> >>>
> >>> But I imagine the case that
> >>>> was in mind when adding this warning was general peer-to-peer
> >>>> between and assigned and emulated device.
> >>> yes makes sense.
> >>>
> >>> Maybe there's an argument to be made
> >>>> that such a p2p mapping might also be used in a non-vIOMMU case. We
> >>>> skip creating those mappings and drivers continue to work, maybe
> >>>> because nobody attempts to do p2p DMA with the types of devices we
> >>>> emulate, maybe because p2p DMA is not absolutely reliable on bare
> >>>> metal and drivers test it before using it.
> >>> MSI doorbells are mapped using the IOMMU_MMIO flag (dma-iommu.c
> >>> iommu_dma_get_msi_page).
> >>> One idea could be to pass that flag through the IOMMU Notifier
> >>> mechanism into the iotlb->perm. Eventually when we get this in
> >>> vfio_get_vaddr() we would not print the warning. Could that make sense?
> >>
> >> Yeah, if we can identify a valid case that doesn't need a warning, that's
> >> fine by me.
> >> Thanks,
> >
> > Let me know if I understood the proposal correctly:
> >
> > virtio-iommu driver in guest will make map (VIRTIO_IOMMU_T_MAP) with
> > VIRTIO_IOMMU_MAP_F_MMIO flag for MSI mapping.
> > In qemu, virtio-iommu device will set a new defined flag (say IOMMU_MMIO)
> > in iotlb->perm in memory_region_notify_iommu(). vfio_get_vaddr() will check
> > same flag and will not print the warning.>
> > Is above correct?
> Yes that's what I had in mind.
In that case virtio-iommu driver in guest should not make map
(VIRTIO_IOMMU_T_MAP) call as it known nothing to be mapped.
Stay Safe
Thanks
-Bharat
>
> Thanks
>
> Eric
> >
> > Thanks
> > -Bharat
> >
> >>
> >> Alex
> >
> >
>
Re: [EXT] Re: [PATCH v9 1/9] hw/vfio/common: Remove error print on mmio region translation by viommu
Hi Bharat,
On 4/2/20 11:01 AM, Bharat Bhushan wrote:
> Hi Eric/Alex,
>
>> -Original Message-
>> From: Alex Williamson
>> Sent: Thursday, March 26, 2020 11:23 PM
>> To: Auger Eric
>> Cc: Bharat Bhushan ; peter.mayd...@linaro.org;
>> pet...@redhat.com; eric.auger@gmail.com; kevin.t...@intel.com;
>> m...@redhat.com; Tomasz Nowicki [C] ;
>> drjo...@redhat.com; linuc.dec...@gmail.com; qemu-devel@nongnu.org; qemu-
>> a...@nongnu.org; bharatb.li...@gmail.com; jean-phili...@linaro.org;
>> yang.zh...@intel.com; David Gibson
>> Subject: [EXT] Re: [PATCH v9 1/9] hw/vfio/common: Remove error print on mmio
>> region translation by viommu
>>
>> External Email
>>
>> --
>> On Thu, 26 Mar 2020 18:35:48 +0100
>> Auger Eric wrote:
>>
>>> Hi Alex,
>>>
>>> On 3/24/20 12:08 AM, Alex Williamson wrote:
>>>> [Cc +dwg who originated this warning]
>>>>
>>>> On Mon, 23 Mar 2020 14:16:09 +0530
>>>> Bharat Bhushan wrote:
>>>>
>>>>> On ARM, the MSI doorbell is translated by the virtual IOMMU.
>>>>> As such address_space_translate() returns the MSI controller MMIO
>>>>> region and we get an "iommu map to non memory area"
>>>>> message. Let's remove this latter.
>>>>>
>>>>> Signed-off-by: Eric Auger
>>>>> Signed-off-by: Bharat Bhushan
>>>>> ---
>>>>> hw/vfio/common.c | 2 --
>>>>> 1 file changed, 2 deletions(-)
>>>>>
>>>>> diff --git a/hw/vfio/common.c b/hw/vfio/common.c index
>>>>> 5ca11488d6..c586edf47a 100644
>>>>> --- a/hw/vfio/common.c
>>>>> +++ b/hw/vfio/common.c
>>>>> @@ -426,8 +426,6 @@ static bool vfio_get_vaddr(IOMMUTLBEntry *iotlb,
>> void **vaddr,
>>>>> , , writable,
>>>>> MEMTXATTRS_UNSPECIFIED);
>>>>> if (!memory_region_is_ram(mr)) {
>>>>> -error_report("iommu map to non memory area %"HWADDR_PRIx"",
>>>>> - xlat);
>>>>> return false;
>>>>> }
>>>>>
>>>>
>>>> I'm a bit confused here, I think we need more justification beyond
>>>> "we hit this warning and we don't want to because it's ok in this
>>>> one special case, therefore remove it". I assume the special case
>>>> is that the device MSI address is managed via the SET_IRQS ioctl and
>>>> therefore we won't actually get DMAs to this range.
>>> Yes exactly. The guest creates a mapping between one giova and this
>>> gpa (corresponding to the MSI controller doorbell) because MSIs are
>>> mapped on ARM. But practically the physical device is programmed with
>>> an host chosen iova that maps onto the physical MSI controller's
>>> doorbell. so the device never performs DMA accesses to this range.
>>>
>>> But I imagine the case that
>>>> was in mind when adding this warning was general peer-to-peer
>>>> between and assigned and emulated device.
>>> yes makes sense.
>>>
>>> Maybe there's an argument to be made
>>>> that such a p2p mapping might also be used in a non-vIOMMU case. We
>>>> skip creating those mappings and drivers continue to work, maybe
>>>> because nobody attempts to do p2p DMA with the types of devices we
>>>> emulate, maybe because p2p DMA is not absolutely reliable on bare
>>>> metal and drivers test it before using it.
>>> MSI doorbells are mapped using the IOMMU_MMIO flag (dma-iommu.c
>>> iommu_dma_get_msi_page).
>>> One idea could be to pass that flag through the IOMMU Notifier
>>> mechanism into the iotlb->perm. Eventually when we get this in
>>> vfio_get_vaddr() we would not print the warning. Could that make sense?
>>
>> Yeah, if we can identify a valid case that doesn't need a warning, that's
>> fine by me.
>> Thanks,
>
> Let me know if I understood the proposal correctly:
>
> virtio-iommu driver in guest will make map (VIRTIO_IOMMU_T_MAP) with
> VIRTIO_IOMMU_MAP_F_MMIO flag for MSI mapping.
> In qemu, virtio-iommu device will set a new defined flag (say IOMMU_MMIO) in
> iotlb->perm in memory_region_notify_iommu(). vfio_get_vaddr() will check same
> flag and will not print the warning.>
> Is above correct?
Yes that's what I had in mind.
Thanks
Eric
>
> Thanks
> -Bharat
>
>>
>> Alex
>
>
RE: [EXT] Re: [PATCH v9 1/9] hw/vfio/common: Remove error print on mmio region translation by viommu
Hi Eric/Alex,
> -Original Message-
> From: Alex Williamson
> Sent: Thursday, March 26, 2020 11:23 PM
> To: Auger Eric
> Cc: Bharat Bhushan ; peter.mayd...@linaro.org;
> pet...@redhat.com; eric.auger@gmail.com; kevin.t...@intel.com;
> m...@redhat.com; Tomasz Nowicki [C] ;
> drjo...@redhat.com; linuc.dec...@gmail.com; qemu-devel@nongnu.org; qemu-
> a...@nongnu.org; bharatb.li...@gmail.com; jean-phili...@linaro.org;
> yang.zh...@intel.com; David Gibson
> Subject: [EXT] Re: [PATCH v9 1/9] hw/vfio/common: Remove error print on mmio
> region translation by viommu
>
> External Email
>
> --
> On Thu, 26 Mar 2020 18:35:48 +0100
> Auger Eric wrote:
>
> > Hi Alex,
> >
> > On 3/24/20 12:08 AM, Alex Williamson wrote:
> > > [Cc +dwg who originated this warning]
> > >
> > > On Mon, 23 Mar 2020 14:16:09 +0530
> > > Bharat Bhushan wrote:
> > >
> > >> On ARM, the MSI doorbell is translated by the virtual IOMMU.
> > >> As such address_space_translate() returns the MSI controller MMIO
> > >> region and we get an "iommu map to non memory area"
> > >> message. Let's remove this latter.
> > >>
> > >> Signed-off-by: Eric Auger
> > >> Signed-off-by: Bharat Bhushan
> > >> ---
> > >> hw/vfio/common.c | 2 --
> > >> 1 file changed, 2 deletions(-)
> > >>
> > >> diff --git a/hw/vfio/common.c b/hw/vfio/common.c index
> > >> 5ca11488d6..c586edf47a 100644
> > >> --- a/hw/vfio/common.c
> > >> +++ b/hw/vfio/common.c
> > >> @@ -426,8 +426,6 @@ static bool vfio_get_vaddr(IOMMUTLBEntry *iotlb,
> void **vaddr,
> > >> , , writable,
> > >> MEMTXATTRS_UNSPECIFIED);
> > >> if (!memory_region_is_ram(mr)) {
> > >> -error_report("iommu map to non memory area %"HWADDR_PRIx"",
> > >> - xlat);
> > >> return false;
> > >> }
> > >>
> > >
> > > I'm a bit confused here, I think we need more justification beyond
> > > "we hit this warning and we don't want to because it's ok in this
> > > one special case, therefore remove it". I assume the special case
> > > is that the device MSI address is managed via the SET_IRQS ioctl and
> > > therefore we won't actually get DMAs to this range.
> > Yes exactly. The guest creates a mapping between one giova and this
> > gpa (corresponding to the MSI controller doorbell) because MSIs are
> > mapped on ARM. But practically the physical device is programmed with
> > an host chosen iova that maps onto the physical MSI controller's
> > doorbell. so the device never performs DMA accesses to this range.
> >
> > But I imagine the case that
> > > was in mind when adding this warning was general peer-to-peer
> > > between and assigned and emulated device.
> > yes makes sense.
> >
> > Maybe there's an argument to be made
> > > that such a p2p mapping might also be used in a non-vIOMMU case. We
> > > skip creating those mappings and drivers continue to work, maybe
> > > because nobody attempts to do p2p DMA with the types of devices we
> > > emulate, maybe because p2p DMA is not absolutely reliable on bare
> > > metal and drivers test it before using it.
> > MSI doorbells are mapped using the IOMMU_MMIO flag (dma-iommu.c
> > iommu_dma_get_msi_page).
> > One idea could be to pass that flag through the IOMMU Notifier
> > mechanism into the iotlb->perm. Eventually when we get this in
> > vfio_get_vaddr() we would not print the warning. Could that make sense?
>
> Yeah, if we can identify a valid case that doesn't need a warning, that's
> fine by me.
> Thanks,
Let me know if I understood the proposal correctly:
virtio-iommu driver in guest will make map (VIRTIO_IOMMU_T_MAP) with
VIRTIO_IOMMU_MAP_F_MMIO flag for MSI mapping.
In qemu, virtio-iommu device will set a new defined flag (say IOMMU_MMIO) in
iotlb->perm in memory_region_notify_iommu(). vfio_get_vaddr() will check same
flag and will not print the warning.
Is above correct?
Thanks
-Bharat
>
> Alex
RE: [EXT] Re: [PATCH v9 1/9] hw/vfio/common: Remove error print on mmio region translation by viommu
Hi Alex, Eric,
> -Original Message-
> From: Alex Williamson
> Sent: Thursday, March 26, 2020 11:23 PM
> To: Auger Eric
> Cc: Bharat Bhushan ; peter.mayd...@linaro.org;
> pet...@redhat.com; eric.auger@gmail.com; kevin.t...@intel.com;
> m...@redhat.com; Tomasz Nowicki [C] ;
> drjo...@redhat.com; linuc.dec...@gmail.com; qemu-devel@nongnu.org; qemu-
> a...@nongnu.org; bharatb.li...@gmail.com; jean-phili...@linaro.org;
> yang.zh...@intel.com; David Gibson
> Subject: [EXT] Re: [PATCH v9 1/9] hw/vfio/common: Remove error print on mmio
> region translation by viommu
>
> External Email
>
> --
> On Thu, 26 Mar 2020 18:35:48 +0100
> Auger Eric wrote:
>
> > Hi Alex,
> >
> > On 3/24/20 12:08 AM, Alex Williamson wrote:
> > > [Cc +dwg who originated this warning]
> > >
> > > On Mon, 23 Mar 2020 14:16:09 +0530
> > > Bharat Bhushan wrote:
> > >
> > >> On ARM, the MSI doorbell is translated by the virtual IOMMU.
> > >> As such address_space_translate() returns the MSI controller MMIO
> > >> region and we get an "iommu map to non memory area"
> > >> message. Let's remove this latter.
> > >>
> > >> Signed-off-by: Eric Auger
> > >> Signed-off-by: Bharat Bhushan
> > >> ---
> > >> hw/vfio/common.c | 2 --
> > >> 1 file changed, 2 deletions(-)
> > >>
> > >> diff --git a/hw/vfio/common.c b/hw/vfio/common.c index
> > >> 5ca11488d6..c586edf47a 100644
> > >> --- a/hw/vfio/common.c
> > >> +++ b/hw/vfio/common.c
> > >> @@ -426,8 +426,6 @@ static bool vfio_get_vaddr(IOMMUTLBEntry *iotlb,
> void **vaddr,
> > >> , , writable,
> > >> MEMTXATTRS_UNSPECIFIED);
> > >> if (!memory_region_is_ram(mr)) {
> > >> -error_report("iommu map to non memory area %"HWADDR_PRIx"",
> > >> - xlat);
> > >> return false;
> > >> }
> > >>
> > >
> > > I'm a bit confused here, I think we need more justification beyond
> > > "we hit this warning and we don't want to because it's ok in this
> > > one special case, therefore remove it". I assume the special case
> > > is that the device MSI address is managed via the SET_IRQS ioctl and
> > > therefore we won't actually get DMAs to this range.
> > Yes exactly. The guest creates a mapping between one giova and this
> > gpa (corresponding to the MSI controller doorbell) because MSIs are
> > mapped on ARM. But practically the physical device is programmed with
> > an host chosen iova that maps onto the physical MSI controller's
> > doorbell. so the device never performs DMA accesses to this range.
> >
> > But I imagine the case that
> > > was in mind when adding this warning was general peer-to-peer
> > > between and assigned and emulated device.
> > yes makes sense.
> >
> > Maybe there's an argument to be made
> > > that such a p2p mapping might also be used in a non-vIOMMU case. We
> > > skip creating those mappings and drivers continue to work, maybe
> > > because nobody attempts to do p2p DMA with the types of devices we
> > > emulate, maybe because p2p DMA is not absolutely reliable on bare
> > > metal and drivers test it before using it.
> > MSI doorbells are mapped using the IOMMU_MMIO flag (dma-iommu.c
> > iommu_dma_get_msi_page).
> > One idea could be to pass that flag through the IOMMU Notifier
> > mechanism into the iotlb->perm. Eventually when we get this in
> > vfio_get_vaddr() we would not print the warning. Could that make sense?
>
> Yeah, if we can identify a valid case that doesn't need a warning, that's
> fine by me.
> Thanks,
Will change as per above suggestion by Eric.
Thanks
-Bharat
>
> Alex
Re: [PATCH v9 1/9] hw/vfio/common: Remove error print on mmio region translation by viommu
On Thu, 26 Mar 2020 18:35:48 +0100
Auger Eric wrote:
> Hi Alex,
>
> On 3/24/20 12:08 AM, Alex Williamson wrote:
> > [Cc +dwg who originated this warning]
> >
> > On Mon, 23 Mar 2020 14:16:09 +0530
> > Bharat Bhushan wrote:
> >
> >> On ARM, the MSI doorbell is translated by the virtual IOMMU.
> >> As such address_space_translate() returns the MSI controller
> >> MMIO region and we get an "iommu map to non memory area"
> >> message. Let's remove this latter.
> >>
> >> Signed-off-by: Eric Auger
> >> Signed-off-by: Bharat Bhushan
> >> ---
> >> hw/vfio/common.c | 2 --
> >> 1 file changed, 2 deletions(-)
> >>
> >> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> >> index 5ca11488d6..c586edf47a 100644
> >> --- a/hw/vfio/common.c
> >> +++ b/hw/vfio/common.c
> >> @@ -426,8 +426,6 @@ static bool vfio_get_vaddr(IOMMUTLBEntry *iotlb, void
> >> **vaddr,
> >> , , writable,
> >> MEMTXATTRS_UNSPECIFIED);
> >> if (!memory_region_is_ram(mr)) {
> >> -error_report("iommu map to non memory area %"HWADDR_PRIx"",
> >> - xlat);
> >> return false;
> >> }
> >>
> >
> > I'm a bit confused here, I think we need more justification beyond "we
> > hit this warning and we don't want to because it's ok in this one
> > special case, therefore remove it". I assume the special case is that
> > the device MSI address is managed via the SET_IRQS ioctl and therefore
> > we won't actually get DMAs to this range.
> Yes exactly. The guest creates a mapping between one giova and this gpa
> (corresponding to the MSI controller doorbell) because MSIs are mapped
> on ARM. But practically the physical device is programmed with an host
> chosen iova that maps onto the physical MSI controller's doorbell. so
> the device never performs DMA accesses to this range.
>
> But I imagine the case that
> > was in mind when adding this warning was general peer-to-peer between
> > and assigned and emulated device.
> yes makes sense.
>
> Maybe there's an argument to be made
> > that such a p2p mapping might also be used in a non-vIOMMU case. We
> > skip creating those mappings and drivers continue to work, maybe
> > because nobody attempts to do p2p DMA with the types of devices we
> > emulate, maybe because p2p DMA is not absolutely reliable on bare metal
> > and drivers test it before using it.
> MSI doorbells are mapped using the IOMMU_MMIO flag (dma-iommu.c
> iommu_dma_get_msi_page).
> One idea could be to pass that flag through the IOMMU Notifier mechanism
> into the iotlb->perm. Eventually when we get this in vfio_get_vaddr() we
> would not print the warning. Could that make sense?
Yeah, if we can identify a valid case that doesn't need a warning,
that's fine by me. Thanks,
Alex
Re: [PATCH v9 1/9] hw/vfio/common: Remove error print on mmio region translation by viommu
Hi Alex,
On 3/24/20 12:08 AM, Alex Williamson wrote:
> [Cc +dwg who originated this warning]
>
> On Mon, 23 Mar 2020 14:16:09 +0530
> Bharat Bhushan wrote:
>
>> On ARM, the MSI doorbell is translated by the virtual IOMMU.
>> As such address_space_translate() returns the MSI controller
>> MMIO region and we get an "iommu map to non memory area"
>> message. Let's remove this latter.
>>
>> Signed-off-by: Eric Auger
>> Signed-off-by: Bharat Bhushan
>> ---
>> hw/vfio/common.c | 2 --
>> 1 file changed, 2 deletions(-)
>>
>> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
>> index 5ca11488d6..c586edf47a 100644
>> --- a/hw/vfio/common.c
>> +++ b/hw/vfio/common.c
>> @@ -426,8 +426,6 @@ static bool vfio_get_vaddr(IOMMUTLBEntry *iotlb, void
>> **vaddr,
>> , , writable,
>> MEMTXATTRS_UNSPECIFIED);
>> if (!memory_region_is_ram(mr)) {
>> -error_report("iommu map to non memory area %"HWADDR_PRIx"",
>> - xlat);
>> return false;
>> }
>>
>
> I'm a bit confused here, I think we need more justification beyond "we
> hit this warning and we don't want to because it's ok in this one
> special case, therefore remove it". I assume the special case is that
> the device MSI address is managed via the SET_IRQS ioctl and therefore
> we won't actually get DMAs to this range.
Yes exactly. The guest creates a mapping between one giova and this gpa
(corresponding to the MSI controller doorbell) because MSIs are mapped
on ARM. But practically the physical device is programmed with an host
chosen iova that maps onto the physical MSI controller's doorbell. so
the device never performs DMA accesses to this range.
But I imagine the case that
> was in mind when adding this warning was general peer-to-peer between
> and assigned and emulated device.
yes makes sense.
Maybe there's an argument to be made
> that such a p2p mapping might also be used in a non-vIOMMU case. We
> skip creating those mappings and drivers continue to work, maybe
> because nobody attempts to do p2p DMA with the types of devices we
> emulate, maybe because p2p DMA is not absolutely reliable on bare metal
> and drivers test it before using it.
MSI doorbells are mapped using the IOMMU_MMIO flag (dma-iommu.c
iommu_dma_get_msi_page).
One idea could be to pass that flag through the IOMMU Notifier mechanism
into the iotlb->perm. Eventually when we get this in vfio_get_vaddr() we
would not print the warning. Could that make sense?
Thanks
Eric
Anyway, I need a better argument
> why this is ok. Thanks,
>
> Alex
>
Re: [PATCH v9 1/9] hw/vfio/common: Remove error print on mmio region translation by viommu
[Cc +dwg who originated this warning]
On Mon, 23 Mar 2020 14:16:09 +0530
Bharat Bhushan wrote:
> On ARM, the MSI doorbell is translated by the virtual IOMMU.
> As such address_space_translate() returns the MSI controller
> MMIO region and we get an "iommu map to non memory area"
> message. Let's remove this latter.
>
> Signed-off-by: Eric Auger
> Signed-off-by: Bharat Bhushan
> ---
> hw/vfio/common.c | 2 --
> 1 file changed, 2 deletions(-)
>
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 5ca11488d6..c586edf47a 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -426,8 +426,6 @@ static bool vfio_get_vaddr(IOMMUTLBEntry *iotlb, void
> **vaddr,
> , , writable,
> MEMTXATTRS_UNSPECIFIED);
> if (!memory_region_is_ram(mr)) {
> -error_report("iommu map to non memory area %"HWADDR_PRIx"",
> - xlat);
> return false;
> }
>
I'm a bit confused here, I think we need more justification beyond "we
hit this warning and we don't want to because it's ok in this one
special case, therefore remove it". I assume the special case is that
the device MSI address is managed via the SET_IRQS ioctl and therefore
we won't actually get DMAs to this range. But I imagine the case that
was in mind when adding this warning was general peer-to-peer between
and assigned and emulated device. Maybe there's an argument to be made
that such a p2p mapping might also be used in a non-vIOMMU case. We
skip creating those mappings and drivers continue to work, maybe
because nobody attempts to do p2p DMA with the types of devices we
emulate, maybe because p2p DMA is not absolutely reliable on bare metal
and drivers test it before using it. Anyway, I need a better argument
why this is ok. Thanks,
Alex
[PATCH v9 1/9] hw/vfio/common: Remove error print on mmio region translation by viommu
On ARM, the MSI doorbell is translated by the virtual IOMMU.
As such address_space_translate() returns the MSI controller
MMIO region and we get an "iommu map to non memory area"
message. Let's remove this latter.
Signed-off-by: Eric Auger
Signed-off-by: Bharat Bhushan
---
hw/vfio/common.c | 2 --
1 file changed, 2 deletions(-)
diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 5ca11488d6..c586edf47a 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -426,8 +426,6 @@ static bool vfio_get_vaddr(IOMMUTLBEntry *iotlb, void
**vaddr,
, , writable,
MEMTXATTRS_UNSPECIFIED);
if (!memory_region_is_ram(mr)) {
-error_report("iommu map to non memory area %"HWADDR_PRIx"",
- xlat);
return false;
}
--
2.17.1
