[PATCH 1/3] virt: acrn: stop using follow_pfn

[Christoph Hellwig <hch@lst.de>]

Switch from follow_pfn to follow_pte so that we can get rid of
follow_pfn.  Note that this doesn't fix any of the pre-existing
raciness and lack of permission checking in the code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/virt/acrn/mm.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/virt/acrn/mm.c b/drivers/virt/acrn/mm.c
index fa5d9ca6be5706..69c3f619f88196 100644
--- a/drivers/virt/acrn/mm.c
+++ b/drivers/virt/acrn/mm.c
@@ -171,18 +171,24 @@ int acrn_vm_ram_map(struct acrn_vm *vm, struct acrn_vm_memmap *memmap)
 	mmap_read_lock(current->mm);
 	vma = vma_lookup(current->mm, memmap->vma_base);
 	if (vma && ((vma->vm_flags & VM_PFNMAP) != 0)) {
+		spinlock_t *ptl;
+		pte_t *ptep;
+
 		if ((memmap->vma_base + memmap->len) > vma->vm_end) {
 			mmap_read_unlock(current->mm);
 			return -EINVAL;
 		}
 
-		ret = follow_pfn(vma, memmap->vma_base, &pfn);
-		mmap_read_unlock(current->mm);
+		ret = follow_pte(vma->vm_mm, memmap->vma_base, &ptep, &ptl);
 		if (ret < 0) {
+			mmap_read_unlock(current->mm);
 			dev_dbg(acrn_dev.this_device,
 				"Failed to lookup PFN at VMA:%pK.\n", (void *)memmap->vma_base);
 			return ret;
 		}
+		pfn = pte_pfn(ptep_get(ptep));
+		pte_unmap_unlock(ptep, ptl);
+		mmap_read_unlock(current->mm);
 
 		return acrn_mm_region_add(vm, memmap->user_vm_pa,
 			 PFN_PHYS(pfn), memmap->len,
-- 
2.39.2