On Thu, May 07, 2020 at 05:24:43PM -0400, Peter Xu wrote: > On Tue, May 05, 2020 at 03:54:44PM -0600, Alex Williamson wrote: > > With conversion to follow_pfn(), DMA mapping a PFNMAP range depends on > > the range being faulted into the vma. Add support to manually provide > > that, in the same way as done on KVM with hva_to_pfn_remapped(). > > > > Signed-off-by: Alex Williamson <[email protected]> > > drivers/vfio/vfio_iommu_type1.c | 36 +++++++++++++++++++++++++++++++++--- > > 1 file changed, 33 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/vfio/vfio_iommu_type1.c > > b/drivers/vfio/vfio_iommu_type1.c > > index cc1d64765ce7..4a4cb7cd86b2 100644 > > +++ b/drivers/vfio/vfio_iommu_type1.c > > @@ -317,6 +317,32 @@ static int put_pfn(unsigned long pfn, int prot) > > return 0; > > } > > > > +static int follow_fault_pfn(struct vm_area_struct *vma, struct mm_struct > > *mm, > > + unsigned long vaddr, unsigned long *pfn, > > + bool write_fault) > > +{ > > + int ret; > > + > > + ret = follow_pfn(vma, vaddr, pfn); > > + if (ret) { > > + bool unlocked = false; > > + > > + ret = fixup_user_fault(NULL, mm, vaddr, > > + FAULT_FLAG_REMOTE | > > + (write_fault ? FAULT_FLAG_WRITE : 0), > > + &unlocked); > > + if (unlocked) > > + return -EAGAIN; > > Hi, Alex, > > IIUC this retry is not needed too because fixup_user_fault() will guarantee > the > fault-in is done correctly with the valid PTE as long as ret==0, even if > unlocked==true.
It is true, and today it is fine, but be careful when reworking this to use notifiers as unlocked also means things like the vma pointer are invalidated. Jason
