Re: [Qemu-devel] [RFC v2 0/8] KVM PCI/MSI passthrough with mach-virt

[Peter Maydell]

On 29 January 2016 at 16:53, Eric Auger <address@hidden> wrote:
> This series enables KVM PCI/MSI passthrough with mach-virt.
>
> A new memory region type is introduced (reserved iova). On
> vfio_listener_region_add this IOVA region is registered to the kernel with
> VFIO_IOMMU_MAP_DMA (using the new VFIO_DMA_MAP_FLAG_MSI_RESERVED_IOVA flag).
>
> The host VFIO PCI driver then can use this IOVA window to map some host
> physical addresses, accessed by passthrough'ed PCI devices, through the IOMMU.
> The first goal is to map host MSI controller frames (GICv2M, GITS_TRANSLATER).
>
> mach-virt currently instantiates a 16x64kB reserved IOVA window. This
> provisions for future usage. Most probably this exceeds MSI binding needs.
> To avoid wasting guest PA, we now map the reserved region onto the
> platform bus MMIO.
>
> The series includes Pranav/Tushar' series:
> QEMU, [v2 0/2] Generic PCIe host bridge INTx determination for INTx routing
> ((https://lists.nongnu.org/archive/html/qemu-devel/2015-04/msg04361.html))
>
> Those patches are not mandated for PCI/MSI passthrough to work but without
> those, the following warning is observed and can puzzle the end-user:
> "qemu-system-aarch64: PCI: Bug - unimplemented PCI INTx routing 
> (gpex-pcihost)"

I've replied with comments about the parts I care about; I'm leaving
the rest of the review to others (VFIO related, etc).

thanks
-- PMM