[PATCH] KVM: arm64: Don't use the VMA to size stage-2 block mappings for VM_PFNMAP

[Mostafa Saleh <smostafa@google.com>]

[ Upstream commit 71cc2c67fb8f8d5aa8154eb482e9846d2214f11b ]

get_vma_page_shift() derives the stage-2 block size for VM_PFNMAP VMAs
from the VMA layout alone, which does not necessarily match what
stage-1 maps for that VMA.

Upstream commit 71cc2c67fb8f ("KVM: arm64: Use stage-1 leaf size for
VM_PFNMAP") drops that calculation and lets transparent_hugepage_adjust()
derive the mapping size from the stage-1 leaf instead. The second part
is not applicable here: in this kernel transparent_hugepage_adjust()
takes a reference on the backing struct page, which is not safe for
MMIO, and stage-1 has no huge PFNMAP before v6.12 anyway. Only drop the
VMA-based calculation, so VM_PFNMAP VMAs are mapped at PAGE_SIZE.

Fixes: 2aa53d68cee6 ("KVM: arm64: Try stage2 block mapping for host device MMIO")
Cc: stable@vger.kernel.org
Signed-off-by: Mostafa Saleh <smostafa@google.com>
---
 arch/arm64/kvm/mmu.c | 25 ++-----------------------
 1 file changed, 2 insertions(+), 23 deletions(-)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 7d04f9670644..c5697cbbfabe 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -904,32 +904,11 @@ transparent_hugepage_adjust(struct kvm *kvm, struct kvm_memory_slot *memslot,
 	return PAGE_SIZE;
 }
 
-static int get_vma_page_shift(struct vm_area_struct *vma, unsigned long hva)
+static int get_vma_page_shift(struct vm_area_struct *vma)
 {
-	unsigned long pa;
-
 	if (is_vm_hugetlb_page(vma) && !(vma->vm_flags & VM_PFNMAP))
 		return huge_page_shift(hstate_vma(vma));
 
-	if (!(vma->vm_flags & VM_PFNMAP))
-		return PAGE_SHIFT;
-
-	VM_BUG_ON(is_vm_hugetlb_page(vma));
-
-	pa = (vma->vm_pgoff << PAGE_SHIFT) + (hva - vma->vm_start);
-
-#ifndef __PAGETABLE_PMD_FOLDED
-	if ((hva & (PUD_SIZE - 1)) == (pa & (PUD_SIZE - 1)) &&
-	    ALIGN_DOWN(hva, PUD_SIZE) >= vma->vm_start &&
-	    ALIGN(hva, PUD_SIZE) <= vma->vm_end)
-		return PUD_SHIFT;
-#endif
-
-	if ((hva & (PMD_SIZE - 1)) == (pa & (PMD_SIZE - 1)) &&
-	    ALIGN_DOWN(hva, PMD_SIZE) >= vma->vm_start &&
-	    ALIGN(hva, PMD_SIZE) <= vma->vm_end)
-		return PMD_SHIFT;
-
 	return PAGE_SHIFT;
 }
 
@@ -1038,7 +1017,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 		force_pte = true;
 		vma_shift = PAGE_SHIFT;
 	} else {
-		vma_shift = get_vma_page_shift(vma, hva);
+		vma_shift = get_vma_page_shift(vma);
 	}
 
 	shared = (vma->vm_flags & VM_SHARED);
-- 
2.56.0.rc1.315.gc6ed9934b7-goog