[PATCH v4.14.y 1/3] vfio/type1: Support faulting PFNMAP vmas

Ajay Kaher
2020-09-07T20:21:13Z

From: Alex Williamson <alex.williamson@redhat.com>

commit 41311242221e3482b20bfed10fa4d9db98d87016 upstream.

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().

Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
[Ajay: Regenerated the patch for v4.14]
Signed-off-by: Ajay Kaher <akaher@vmware.com>
---
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 35a3750..150be10 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -336,6 +336,32 @@ 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;
+
+ if (ret)
+ return ret;
+
+ ret = follow_pfn(vma, vaddr, pfn);
+ }
+
+ return ret;
+}
+
static int vaddr_get_pfn(struct mm_struct *mm, unsigned long vaddr,
int prot, unsigned long *pfn)
{
@@ -375,12 +401,16 @@ static int vaddr_get_pfn(struct mm_struct *mm, unsigned long vaddr,

down_read(&mm->mmap_sem);

+retry:
vma = find_vma_intersection(mm, vaddr, vaddr + 1);

if (vma && vma->vm_flags & VM_PFNMAP) {
- if (!follow_pfn(vma, vaddr, pfn) &&
- is_invalid_reserved_pfn(*pfn))
- ret = 0;
+ ret = follow_fault_pfn(vma, mm, vaddr, pfn, prot & IOMMU_WRITE);
+ if (ret == -EAGAIN)
+ goto retry;
+
+ if (!ret && !is_invalid_reserved_pfn(*pfn))
+ ret = -EFAULT;
}

up_read(&mm->mmap_sem);
--
2.7.4