Hey Steve, how did you get around this for cpr or is this a gap?
Thanks,
Alex
On Mon, 27 Jun 2022 11:51:09 +0800
lizhe.67@xxxxxxxxxxxxx wrote:
> From: Li Zhe <lizhe.67@xxxxxxxxxxxxx>
>
> In function vfio_dma_do_unmap(), we currently prevent process to unmap
> vfio dma region whose mm_struct is different from the vfio_dma->task.
> In our virtual machine scenario which is using kvm and qemu, this
> judgement stops us from liveupgrading our qemu, which uses fork() &&
> exec() to load the new binary but the new process cannot do the
> VFIO_IOMMU_UNMAP_DMA action during vm exit because of this judgement.
>
> This judgement is added in commit 8f0d5bb95f76 ("vfio iommu type1: Add
> task structure to vfio_dma") for the security reason. But it seems that
> no other task who has no family relationship with old and new process
> can get the same vfio_dma struct here for the reason of resource
> isolation. So this patch delete it.
>
> Signed-off-by: Li Zhe <lizhe.67@xxxxxxxxxxxxx>
> Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxx>
> ---
> drivers/vfio/vfio_iommu_type1.c | 6 ------
> 1 file changed, 6 deletions(-)
>
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index c13b9290e357..a8ff00dad834 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -1377,12 +1377,6 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
>
> if (!iommu->v2 && iova > dma->iova)
> break;
> - /*
> - * Task with same address space who mapped this iova range is
> - * allowed to unmap the iova range.
> - */
> - if (dma->task->mm != current->mm)
> - break;
>
> if (invalidate_vaddr) {
> if (dma->vaddr_invalid) {
