On Wed, 10 Mar 2021 14:14:46 -0400
Jason Gunthorpe <j...@nvidia.com> wrote:
> On Wed, Mar 10, 2021 at 10:53:29AM -0700, Alex Williamson wrote:
>
> > diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> > index 65e7e6b44578..ae723808e08b 100644
> > +++ b/drivers/vfio/pci/vfio_pci.c
> > @@ -1573,6 +1573,11 @@ static int __vfio_pci_add_vma(struct vfio_pci_device
> > *vdev,
> > {
> > struct vfio_pci_mmap_vma *mmap_vma;
> >
> > + list_for_each_entry(mmap_vma, &vdev->vma_list, vma_next) {
> > + if (mmap_vma->vma == vma)
> > + return 0; /* Swallow the error, the vma is tracked */
> > + }
> > +
> > mmap_vma = kmalloc(sizeof(*mmap_vma), GFP_KERNEL);
> > if (!mmap_vma)
> > return -ENOMEM;
> > @@ -1612,31 +1617,32 @@ static vm_fault_t vfio_pci_mmap_fault(struct
> > vm_fault *vmf)
> > {
> > struct vm_area_struct *vma = vmf->vma;
> > struct vfio_pci_device *vdev = vma->vm_private_data;
> > - vm_fault_t ret = VM_FAULT_NOPAGE;
> > + unsigned long vaddr = vma->vm_start, pfn = vma->vm_pgoff;
> > + vm_fault_t ret = VM_FAULT_SIGBUS;
> >
> > mutex_lock(&vdev->vma_lock);
> > down_read(&vdev->memory_lock);
> >
> > - if (!__vfio_pci_memory_enabled(vdev)) {
> > - ret = VM_FAULT_SIGBUS;
> > - mutex_unlock(&vdev->vma_lock);
> > + if (!__vfio_pci_memory_enabled(vdev))
> > goto up_out;
> > +
> > + for (; vaddr < vma->vm_end; vaddr += PAGE_SIZE, pfn++) {
> > + ret = vmf_insert_pfn_prot(vma, vaddr, pfn,
> > + pgprot_decrypted(vma->vm_page_prot));
> >
>
> I investigated this, I think the above pgprot_decrypted() should be
> moved here:
>
> static int vfio_pci_mmap(void *device_data, struct vm_area_struct *vma)
> {
> vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
> + vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);
>
>
> And since:
>
> vm_fault_t vmf_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
> unsigned long pfn)
> {
> return vmf_insert_pfn_prot(vma, addr, pfn, vma->vm_page_prot);
>
> The above can just use vfm_insert_pfn()
Cool, easy enough. Thanks for looking.
> The only thing that makes me nervous about this arrangment is loosing
> the track_pfn_remap() which was in remap_pfn_range() - I think it
> means we miss out on certain PAT manipulations.. I *suspect* this is
> not a problem for VFIO because it will rely on the MTRRs generally on
> x86 - but I also don't know this mechanim too well.
Yeah, for VM use cases the MTRRs generally override.
> I think after the address_space changes this should try to stick with
> a normal io_rmap_pfn_range() done outside the fault handler.
I assume you're suggesting calling io_remap_pfn_range() when device
memory is enabled, do you mean using vma_interval_tree_foreach() like
unmap_mapping_range() does to avoid re-adding a vma list? Thanks,
Alex
