Re: [PATCH v2 1/3] s390/pci: Fix s390_mmio_read/write syscall page fault handling

Matthew Rosato
2024-05-28T15:13:16Z

On 5/23/24 7:10 AM, Niklas Schnelle wrote:
> The s390 MMIO syscalls when using the classic PCI instructions do not
> cause a page fault when follow_pte() fails due to the page not being
> present. Besides being a general deficiency this breaks vfio-pci's mmap()
> handling once VFIO_PCI_MMAP gets enabled as this lazily maps on first
> access. Fix this by following a failed follow_pte() with
> fixup_user_page() and retrying the follow_pte().
>
> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
> Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>

Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>

FYI, as of -rc1 this patch has a merge conflict with 29ae7d96d166 ("mm: pass VMA instead of MM to follow_pte().")