[PATCH v2 07/30] KVM: arm64: Simplify nested VMA shift calculation

[Marc Zyngier]

From: Fuad Tabba <tabba at google.com>

In the kvm_s2_resolve_vma_size() helper, the local variable vma_pagesize
is calculated from vma_shift, only to be used to bound the vma_pagesize
by max_map_size and subsequently convert it back to a shift via __ffs().

Because vma_pagesize and max_map_size are both powers of two, we can
simplify the logic by omitting vma_pagesize entirely and bounding the
vma_shift directly using the shift of max_map_size. This achieves the
same result while keeping the size-to-shift conversion out of the helper
logic.

Signed-off-by: Fuad Tabba <tabba at google.com>
Signed-off-by: Marc Zyngier <maz at kernel.org>
---
 arch/arm64/kvm/mmu.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 164f1160ea33d..5572b127f8663 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1646,7 +1646,6 @@ static short kvm_s2_resolve_vma_size(struct vm_area_struct *vma,
 				     bool *force_pte, phys_addr_t *ipa)
 {
 	short vma_shift;
-	long vma_pagesize;
 
 	if (*force_pte)
 		vma_shift = PAGE_SHIFT;
@@ -1677,8 +1676,6 @@ static short kvm_s2_resolve_vma_size(struct vm_area_struct *vma,
 		WARN_ONCE(1, "Unknown vma_shift %d", vma_shift);
 	}
 
-	vma_pagesize = 1UL << vma_shift;
-
 	if (nested) {
 		unsigned long max_map_size;
 
@@ -1703,8 +1700,7 @@ static short kvm_s2_resolve_vma_size(struct vm_area_struct *vma,
 			max_map_size = PAGE_SIZE;
 
 		*force_pte = (max_map_size == PAGE_SIZE);
-		vma_pagesize = min_t(long, vma_pagesize, max_map_size);
-		vma_shift = __ffs(vma_pagesize);
+		vma_shift = min_t(short, vma_shift, __ffs(max_map_size));
 	}
 
 	return vma_shift;
-- 
2.47.3