Re: [PATCH 0/6] virtio-iommu: Add ACPI support

[Jean-Philippe Brucker]

Hi Eric,

On Tue, Aug 17, 2021 at 04:58:01PM +0200, Eric Auger wrote:
> Hi Jean,
> 
> On 8/10/21 10:45 AM, Jean-Philippe Brucker wrote:
> > Allow instantiating a virtio-iommu device on ACPI systems by adding a
> > Virtual I/O Translation table (VIOT). Enable x86 support for VIOT.
> 
> Don't you need your other patch
> "virtio-iommu: Default to bypass during boot"?
> 
> Without this latter, for me the guest fails to boot.

Good point, I think I've been lucky during my testing. My bootloader and
kernel are on virtio-blk-pci devices and as I wasn't explicitly enabling
the "iommu_platform" parameter, they would bypass the IOMMU. When enabling
the parameter, boot hangs since the IOMMU isn't enabled when the
bootloader needs to fetch the kernel, and DMA faults. That parameter is
specific to virtio devices. Using another storage for bootloader and
kernel will result in failure to boot.

I've been postponing the boot-bypass patch since it requires a
specification change to be done right, but it's next on my list.

Thanks,
Jean