Re: [PATCH 0/5] Convert virtio-iommu to domain_alloc_paging()

Jean-Philippe Brucker
2025-02-12T19:15:40Z

On Wed, Feb 12, 2025 at 09:05:35AM -0800, Jacob Pan wrote:
> > Does reproducing this require
> > modifying QEMU or Linux to disable support for F_BYPASS_CONFIG, or
> > just passing QEMU/kernel parameters?
> I only modified guest code to pretend F_BYPASS_CONFIG is not supported,
> a couple of places like:
>
> - if (virtio_has_feature(viommu->vdev,
> VIRTIO_IOMMU_F_BYPASS_CONFIG)) {
> + if (!virtio_has_feature(viommu->vdev,
> VIRTIO_IOMMU_F_BYPASS_CONFIG)) {
>
> Is there a QEMU command line option to disable
> VIRTIO_IOMMU_F_BYPASS_CONFIG?

No, but I have a patch for testing that didn't seem worth upstreaming:
https://jpbrucker.net/git/qemu/commit/?h=virtio-iommu/bypass&id=ab2f435576a95914d2939ef4f0b190548721fe7b
With it I'm able to reproduce the issue, looks like I only tested this
case with virtual devices and not VFIO. I'll look for a fix

Thanks,
Jean