Re: [PATCH] KVM: arm64: nv: Invalidate whole L1 blocks on TLBI RIPAS2E1

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Low] KVM: arm64: nv: multiple evaluation of compute_tlb_inval_range()
  in ALIGN*()
--

commit a02572444c705de05e0b8656d139113ddf1c61f9
Author: Dan Carpenter <dan@cryspen.com>

KVM: arm64: nv: Invalidate whole L1 blocks on TLBI RIPAS2E1

This commit widens the range unmapped by s2_mmu_unmap_range() to cover
the containing L1 stage-2 blocks using compute_tlb_inval_range().

> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 5ee1b521d2b3f..ef4554656ddfb 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -4116,6 +4116,17 @@ union tlbi_info {
>  static void s2_mmu_unmap_range(struct kvm_s2_mmu *mmu,
>  			       const union tlbi_info *info)
>  {
> +	u64 start = info->range.start;
> +	u64 end = start + info->range.size;
> +
> +	/*
> +	 * An L1 stage-2 block may be held in the shadow S2 as several smaller
> +	 * leaves, and R_TVTYQ requires the TLBI to invalidate all of them, so
> +	 * widen each end of the range to the L1 block containing it.
> +	 */
> +	start = ALIGN_DOWN(start, compute_tlb_inval_range(mmu, start >> 12));
> +	end = ALIGN(end, compute_tlb_inval_range(mmu, (end - 1) >> 12));

[Severity: Low]
Does passing compute_tlb_inval_range() directly to ALIGN_DOWN() and
ALIGN() evaluate it five times instead of twice?  ALIGN_DOWN(x, a)
expands a three times and ALIGN(x, a) expands a twice via
__ALIGN_KERNEL() and __ALIGN_KERNEL_MASK(), so each call to
s2_mmu_unmap_range() performs three redundant sets of shadow stage-2
page-table lookups under kvm->mmu_lock.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/6817d113e5f0a9cafe0ce5bc0847276b7f14aacc.1794210561.git.dan@cryspen.com?part=1