[PATCH 1/3] KVM: arm64: Don't defer TLB invalidation when zapping table entries
Will Deacon
will at kernel.org
Mon Mar 25 11:51:56 PDT 2024
Commit 7657ea920c54 ("KVM: arm64: Use TLBI range-based instructions for
unmap") introduced deferred TLB invalidation for the stage-2 page-table
so that range-based invalidation can be used for the accumulated
addresses. This works fine if the structure of the page-tables remains
unchanged, but if entire tables are zapped and subsequently freed then
we transiently leave the hardware page-table walker with a reference
to freed memory thanks to the translation walk caches. For example,
stage2_unmap_walker() will free page-table pages:
if (childp)
mm_ops->put_page(childp);
and issue the TLB invalidation later in kvm_pgtable_stage2_unmap():
if (stage2_unmap_defer_tlb_flush(pgt))
/* Perform the deferred TLB invalidations */
kvm_tlb_flush_vmid_range(pgt->mmu, addr, size);
For now, take the conservative approach and invalidate the TLB eagerly
when we clear a table entry.
Cc: Raghavendra Rao Ananta <rananta at google.com>
Cc: Shaoqin Huang <shahuang at redhat.com>
Cc: Marc Zyngier <maz at kernel.org>
Cc: Oliver Upton <oliver.upton at linux.dev>
Signed-off-by: Will Deacon <will at kernel.org>
---
arch/arm64/kvm/hyp/pgtable.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index 3fae5830f8d2..de0b667ba296 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -896,9 +896,11 @@ static void stage2_unmap_put_pte(const struct kvm_pgtable_visit_ctx *ctx,
if (kvm_pte_valid(ctx->old)) {
kvm_clear_pte(ctx->ptep);
- if (!stage2_unmap_defer_tlb_flush(pgt))
+ if (!stage2_unmap_defer_tlb_flush(pgt) ||
+ kvm_pte_table(ctx->old, ctx->level)) {
kvm_call_hyp(__kvm_tlb_flush_vmid_ipa, mmu,
ctx->addr, ctx->level);
+ }
}
mm_ops->put_page(ctx->ptep);
--
2.44.0.396.g6e790dbe36-goog
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