From: Will Deacon <will@kernel.org>
To: kvmarm@lists.linux.dev
Cc: linux-arm-kernel@lists.infradead.org,
	Will Deacon <will@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Gavin Shan <gshan@redhat.com>,
	Marc Zyngier <maz@kernel.org>,
	Mostafa Saleh <smostafa@google.com>,
	Oliver Upton <oliver.upton@linux.dev>,
	Quentin Perret <qperret@google.com>,
	Raghavendra Rao Ananta <rananta@google.com>,
	Ryan Roberts <ryan.roberts@arm.com>,
	Shaoqin Huang <shahuang@redhat.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Zenghui Yu <yuzenghui@huawei.com>
Subject: [PATCH 1/3] KVM: arm64: Don't defer TLB invalidation when zapping table entries
Date: Mon, 25 Mar 2024 18:51:56 +0000
Message-Id: <20240325185158.8565-2-will@kernel.org>
In-Reply-To: <20240325185158.8565-1-will@kernel.org>
References: <20240325185158.8565-1-will@kernel.org>
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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@google.com>
Cc: Shaoqin Huang <shahuang@redhat.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Will Deacon <will@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