Hi Alex, On 24/01/18 16:02, Alex Williamson wrote: > On Wed, 24 Jan 2018 15:13:06 +0100 > Auger Eric <eric.au...@redhat.com> wrote: > >> Hi Alex, >> On 23/01/18 20:55, Alex Williamson wrote: >>> On Tue, 23 Jan 2018 16:34:34 +0100 >>> Auger Eric <eric.au...@redhat.com> wrote: >>> >>>> Hi Alexey, >>>> On 23/01/18 02:22, Alexey Kardashevskiy wrote: >>>>> This makes use of a new VFIO_REGION_INFO_CAP_MSIX_MAPPABLE capability >>>>> which tells that a region with MSIX data can be mapped entirely, i.e. >>>>> the VFIO PCI driver won't prevent MSIX vectors area from being mapped. >>>>> >>>>> With this change, all BARs are mapped in a single chunk and MSIX vectors >>>>> are emulated on top unless the machine requests not to by defining and >>>>> enabling a new "vfio-no-msix-emulation" property. At the moment only >>>>> sPAPR machine does so - it prohibits MSIX emulation and does not allow >>>>> enabling it as it does not define the "set" callback for the new property; >>>>> the new property also does not appear in "-machine pseries,help". >>>>> >>>>> If MSIX vectors section is not aligned to the page size, the KVM memory >>>>> listener does not register it with the KVM as a memory slot and MSIX is >>>>> emulated by QEMU as before. This may create MMIO RAM memory sections with >>>>> an address or/and a size not aligned which will make vfio_dma_map() fail; >>>>> to address this, this makes treats such failures as non-fatal. >>>>> >>>>> This requires the kernel change - "vfio-pci: Allow mapping MSIX BAR" - >>>>> for the new capability: https://www.spinics.net/lists/kvm/msg160282.html >>>>> >>>>> Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru> >>>>> --- >>>>> Changes: >>>>> v3: >>>>> * vfio_listener_region_add() won't make qemu exit if failed on MMIO MR >>>>> >>>>> --- >>>>> include/hw/vfio/vfio-common.h | 1 + >>>>> linux-headers/linux/vfio.h | 5 +++++ >>>>> hw/ppc/spapr.c | 7 +++++++ >>>>> hw/vfio/common.c | 19 +++++++++++++++++++ >>>>> hw/vfio/pci.c | 10 ++++++++++ >>>>> 5 files changed, 42 insertions(+) >>>>> >>>>> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h >>>>> index f3a2ac9..927d600 100644 >>>>> --- a/include/hw/vfio/vfio-common.h >>>>> +++ b/include/hw/vfio/vfio-common.h >>>>> @@ -171,6 +171,7 @@ int vfio_get_region_info(VFIODevice *vbasedev, int >>>>> index, >>>>> struct vfio_region_info **info); >>>>> int vfio_get_dev_region_info(VFIODevice *vbasedev, uint32_t type, >>>>> uint32_t subtype, struct vfio_region_info >>>>> **info); >>>>> +bool vfio_is_cap_present(VFIODevice *vbasedev, uint16_t cap_type, int >>>>> region); >>>>> #endif >>>>> extern const MemoryListener vfio_prereg_listener; >>>>> >>>>> diff --git a/linux-headers/linux/vfio.h b/linux-headers/linux/vfio.h >>>>> index 4312e96..b45182e 100644 >>>>> --- a/linux-headers/linux/vfio.h >>>>> +++ b/linux-headers/linux/vfio.h >>>>> @@ -301,6 +301,11 @@ struct vfio_region_info_cap_type { >>>>> #define VFIO_REGION_SUBTYPE_INTEL_IGD_HOST_CFG (2) >>>>> #define VFIO_REGION_SUBTYPE_INTEL_IGD_LPC_CFG (3) >>>>> >>>>> +/* >>>>> + * The MSIX mappable capability informs that MSIX data of a BAR can be >>>>> mmapped. >>>>> + */ >>>>> +#define VFIO_REGION_INFO_CAP_MSIX_MAPPABLE 3 >>>>> + >>>>> /** >>>>> * VFIO_DEVICE_GET_IRQ_INFO - _IOWR(VFIO_TYPE, VFIO_BASE + 9, >>>>> * struct vfio_irq_info) >>>>> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c >>>>> index d1acfe8..5ff43ce 100644 >>>>> --- a/hw/ppc/spapr.c >>>>> +++ b/hw/ppc/spapr.c >>>>> @@ -2789,6 +2789,11 @@ static void spapr_set_modern_hotplug_events(Object >>>>> *obj, bool value, >>>>> spapr->use_hotplug_event_source = value; >>>>> } >>>>> >>>>> +static bool spapr_get_msix_emulation(Object *obj, Error **errp) >>>>> +{ >>>>> + return true; >>>>> +} >>>>> + >>>>> static char *spapr_get_resize_hpt(Object *obj, Error **errp) >>>>> { >>>>> sPAPRMachineState *spapr = SPAPR_MACHINE(obj); >>>>> @@ -2870,6 +2875,8 @@ static void spapr_instance_init(Object *obj) >>>>> object_property_set_description(obj, "vsmt", >>>>> "Virtual SMT: KVM behaves as if this >>>>> were" >>>>> " the host's SMT mode", >>>>> &error_abort); >>>>> + object_property_add_bool(obj, "vfio-no-msix-emulation", >>>>> + spapr_get_msix_emulation, NULL, NULL); >>>>> } >>>>> >>>>> static void spapr_machine_finalizefn(Object *obj) >>>>> diff --git a/hw/vfio/common.c b/hw/vfio/common.c >>>>> index b77be3a..842c5b2 100644 >>>>> --- a/hw/vfio/common.c >>>>> +++ b/hw/vfio/common.c >>>>> @@ -530,6 +530,10 @@ static void vfio_listener_region_add(MemoryListener >>>>> *listener, >>>>> return; >>>>> >>>>> fail: >>>>> + if (memory_region_is_ram_device(section->mr)) { >>>>> + error_report("failed to vfio_dma_map. pci p2p may not work"); >>>>> + return; >>>>> + } >>>> >>>> I don't think this is an acceptable solution as it produces plenty of >>>> errors such as >>>> >>>> qemu-system-aarch64: VFIO_MAP_DMA: -22 >>>> qemu-system-aarch64: vfio_dma_map(0x30a7ab90, 0x8000000000, 0x2000, >>>> 0xfffd79a00000) = -22 (Invalid argument) >>> >>> This much of the error above could be avoided by looking at the type1 >>> page size bitmap before trying to perform the mapping. >>> >>>> qemu-system-aarch64: failed to vfio_dma_map. pci p2p may not work >>> >>> This of course is still valid though we can continue to discuss if it's >>> worthwhile user information. >>> >>>> testing context is: aarch64 + Mellanox CX-4 PF where we still try to map >>>> the BAR0 area [0 - 0x2000] before the MSI-X table which is not aligned >>>> with the host 64kB page. >>>> >>>> Region 0: Memory at 80400000000 (64-bit, prefetchable) [size=32M] >>>> Capabilities: [9c] MSI-X: Enable+ Count=64 Masked- >>>> Vector table: BAR=0 offset=00002000 >>>> PBA: BAR=0 offset=00003000 >>>> >>>> >>>> To me a kind of mmaps region fixup looks required? >>> >>> I don't think so. vfio is now telling us that we can mmap the entire >>> BAR, this is true. The type1 info is telling us that the minimum DMA >>> mapping granularity, PAGE_SIZE on the host (64K in your case). The >>> MSI-X offset on this device introduces an 8K range that type1 cannot >>> map and QEMU already has all the information it needs to know this. The >>> solutions are either to move MSI-X elsewhere or to extend type1 to >>> allow DMA mappings down to the IOMMU minimum granularity. >>> >>> The MSI-X fixup that is now bypassed avoided this not generating an >>> mmap over the vector table, which meant this 8K region wasn't covered >>> by a memory slot and therefore never got passed through region_add. So >>> p2p dma was silently disabled. Now we do mmap the entire BAR, but we >>> add the MSI-X region on top of it so that when it gets flattened we end >>> up with these sub-page slots. Skipping them at region_add has the same >>> overall effect. >>> >>> Before: >>> >>> |-| <-- MSI-X vector emulation MR >>> + >>> |---PAGE_SIZE aligned mmap MR----| >>> + >>> |------------slow mapped BAR M------------| >>> >>> = >>> >>> |----Resulting region_add--------| (PAGE_SIZE aligned) >>> >>> After: >>> >>> |-| <-- MSI-X vector emulation MR >>> + >>> |------------PAGE_SIZE aligned mmap MR----| >>> + >>> |------------slow mapped BAR M------------| >>> >>> = >>> >>> |-| |----Resulting region_add-------------| (Gap no longer PAGE_SIZE >>> aligned) >>> >>> So doesn't it make sense that region_add would now filter these out? >>> Should we continue to silently skip unmapped MMIO? Thanks, >> >> I am confused because I don't see the vfio_region_read/write for >> segments whose mmap failed. Nevertheless the assignment looks to work >> properly. > > Segments whose mmap failed or whose dma map failed? dma map sorry When we have the > "after" case above, the ram_device mmap covers the entire direct access > range to the device, therefore the flattened view will hit those > MemoryRegion.ops first, which will be ram_device_mem_ops. Ah OK this is the piece I was missing.
OK so above description makes sense to me. However at the moment the user doesn't get a clear indication about what's wrong and this is what I pointed out first. Thanks Eric Thanks Eric We'll only > get to vfio_region_ops in the "before" case where the flattened map > exposes the slow MR. Thanks, > > Alex >