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Re: [Qemu-ppc] [PATCH qemu 2/5] vfio: Skip PCI BARs in memory listener
From: |
Alex Williamson |
Subject: |
Re: [Qemu-ppc] [PATCH qemu 2/5] vfio: Skip PCI BARs in memory listener |
Date: |
Mon, 13 Jul 2015 11:08:40 -0600 |
On Fri, 2015-07-10 at 20:43 +1000, Alexey Kardashevskiy wrote:
> In some cases PCI BARs are registered as RAM via
> memory_region_init_ram_ptr() and the vfio_memory_listener will be called
> on them too. However DMA will not be performed to/from these regions so
> just skip them.
Who says? What about peer-to-peer DMA? We have all sorts of FUD about
whether the hardware handles this correctly, but mapping PCI MMIO BARs
into the IOMMU allows the possibility of supporting p2p DMA between
devices in the guest. Thanks,
Alex
>
> Signed-off-by: Alexey Kardashevskiy <address@hidden>
> ---
> hw/vfio/common.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index d115ec9..225cdc7 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -248,7 +248,8 @@ static bool
> vfio_listener_skipped_section(MemoryRegionSection *section)
> * are never accessed by the CPU and beyond the address width of
> * some IOMMU hardware. TODO: VFIO should tell us the IOMMU
> width.
> */
> - section->offset_within_address_space & (1ULL << 63);
> + section->offset_within_address_space & (1ULL << 63) ||
> + memory_region_is_skip_dump(section->mr);
> }
>
> static void vfio_iommu_map_notify(Notifier *n, void *data)
- [Qemu-ppc] [PATCH qemu 0/5] vfio: SPAPR IOMMU v2 (memory preregistration support), Alexey Kardashevskiy, 2015/07/10
- [Qemu-ppc] [PATCH qemu 4/5] vfio: Refactor memory listener to accommodate more IOMMU types, Alexey Kardashevskiy, 2015/07/10
- [Qemu-ppc] [PATCH qemu 1/5] vfio: Switch from TARGET_PAGE_MASK to qemu_real_host_page_mask, Alexey Kardashevskiy, 2015/07/10
- [Qemu-ppc] [PATCH qemu 3/5] vfio: Store IOMMU type in container, Alexey Kardashevskiy, 2015/07/10
- [Qemu-ppc] [PATCH qemu 2/5] vfio: Skip PCI BARs in memory listener, Alexey Kardashevskiy, 2015/07/10
- Re: [Qemu-ppc] [PATCH qemu 2/5] vfio: Skip PCI BARs in memory listener,
Alex Williamson <=
- [Qemu-ppc] [PATCH qemu 5/5] vfio: spapr: Add SPAPR IOMMU v2 support (DMA memory preregistering), Alexey Kardashevskiy, 2015/07/10