Re: [PATCH v3 0/2] amd_iommu: Fixes

[Michael S. Tsirkin]

On Fri, May 16, 2025 at 03:35:33PM +0530, Sairaj Kodilkar wrote:
> Fix following two issues in the amd viommu
> 1. The guest fails to setup the passthrough device when for following setup
>    because amd iommu enables the no DMA memory region even when guest is 
>    using DMA remapping mode.
> 
>     -device amd-iommu,intremap=on,xtsup=on,pt=on \
>     -device vfio-pci,host=<DEVID> \
> 
>     and guest forcing DMA remap mode e.g. 'iommu.passthrough=0'
> 
>     which will cause failures from QEMU:
> 
>     qemu-system-x86_64: AHCI: Failed to start DMA engine: bad command list 
> buffer address
>     qemu-system-x86_64: AHCI: Failed to start FIS receive engine: bad FIS 
> receive buffer address
>     qemu-system-x86_64: AHCI: Failed to start DMA engine: bad command list 
> buffer address
>     qemu-system-x86_64: AHCI: Failed to start FIS receive engine: bad FIS 
> receive buffer address
>     qemu-system-x86_64: AHCI: Failed to start DMA engine: bad command list 
> buffer address
> 
> 
> 2. The guest fails to boot with xtsup=on and <= 255 vCPUs, because amd_iommu
>    does not enable x2apic mode.
> 
> base commit 56c6e249b6988c1b6edc2dd34ebb0f1e570a1365 (v10.0.0-rc3)
> 
> Sairaj Kodilkar (1):
>   hw/i386/amd_iommu: Fix device setup failure when PT is on.
> 
> Vasant Hegde (1):
>   hw/i386/amd_iommu: Fix xtsup when vcpus < 255
> 
>  hw/i386/amd_iommu.c | 20 ++++++++++----------
>  1 file changed, 10 insertions(+), 10 deletions(-)

changelog?

> -- 
> 2.34.1