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. Thanks Eric > > Alex >