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KVM: arm64: Simplify nested VMA shift calculation

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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@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Fuad Tabba 2026-03-06 14:02:26 +00:00 committed by Marc Zyngier
parent 5557a3f843
commit 2175ca5384
1 changed files with 1 additions and 5 deletions
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6
arch/arm64/kvm/mmu.c
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@ -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;