Re: [regression 6.1.y] Regression from 476c1dfefab8 ("mm: Don't pin ZERO_PAGE in pin_user_pages()") with pci-passthrough for both KVM VMs and booting in xen DomU

[Milan Broz]

On 4/15/25 8:59 PM, Salvatore Bonaccorso wrote:
> Milan verified that the issue persists in 6.1.134 so far and the patch
> itself cannot be just reverted.

Just an update:

With 6.1.134 stable as a base, I reverted that commit (upstream c8070b78751955e59b42457b974bea4a4fe00187)
+ applied upstream commit 873aefb376bbc0ed1dd2381ea1d6ec88106fdbd4 (vfio/type1: Unpin zero pages)
+ reverted upstream bddf10d26e6e5114e7415a0e442ec6f51a559468 (uprobes: Reject the shared zeropage in uprobe_write_opcode())
to be able compile code without errors.

With these changes, kernel works with my NVMe passthrough test again. This confirms the issue.

Milan

> The failures all have a similar pattern, when pci-passthrough is used
> for a pci devide, for instance under qemu the bootup will fail with:
>
> qemu-system-x86_64: -device {"driver":"vfio-pci","host":"0000:03:00.0","id":"hostdev0","bus":"pci.3","addr":"0x0"}: VFIO_MAP_DMA failed: Cannot allocate memory
> qemu-system-x86_64: -device {"driver":"vfio-pci","host":"0000:03:00.0","id":"hostdev0","bus":"pci.3","addr":"0x0"}: vfio 0000:03:00.0: failed to setup container
>
> (in the case as reported by Milan).
>
> Any ideas here?
>
> Regards,
> Salvatore