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

[Jason Gunthorpe]

On Tue, May 21, 2024 at 02:14:57PM +0200, 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().
> 
> Signed-off-by: Niklas Schnelle <schnelle@xxxxxxxxxxxxx>
> ---
>  arch/s390/pci/pci_mmio.c | 18 +++++++++++++-----
>  1 file changed, 13 insertions(+), 5 deletions(-)

Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>

Jason