linux-kernel - [PATCH v4 5/6] KVM: arm64: Invalidate the table entries upon a range

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Date:   Fri, 19 May 2023 00:52:30 +0000
From:   Raghavendra Rao Ananta <rananta@...gle.com>
To:     Oliver Upton <oliver.upton@...ux.dev>,
        Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>
Cc:     Ricardo Koller <ricarkol@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jing Zhang <jingzhangos@...gle.com>,
        Colton Lewis <coltonlewis@...gle.com>,
        Raghavendra Rao Anata <rananta@...gle.com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: [PATCH v4 5/6] KVM: arm64: Invalidate the table entries upon a range

Currently, during the operations such as a hugepage collapse,
KVM would flush the entire VM's context using 'vmalls12e1is'
TLBI operation. Specifically, if the VM is faulting on many
hugepages (say after dirty-logging), it creates a performance
penalty for the guest whose pages have already been faulted
earlier as they would have to refill their TLBs again.

Instead, call __kvm_tlb_flush_vmid_range() for table entries.
If the system supports it, only the required range will be
flushed. Else, it'll fallback to the previous mechanism.

Signed-off-by: Raghavendra Rao Ananta <rananta@...gle.com>
---
 arch/arm64/kvm/hyp/pgtable.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index 3d61bd3e591d2..b8f0dbd12f773 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -745,10 +745,13 @@ static bool stage2_try_break_pte(const struct kvm_pgtable_visit_ctx *ctx,
 	 * Perform the appropriate TLB invalidation based on the evicted pte
 	 * value (if any).
 	 */
-	if (kvm_pte_table(ctx->old, ctx->level))
-		kvm_call_hyp(__kvm_tlb_flush_vmid, mmu);
-	else if (kvm_pte_valid(ctx->old))
+	if (kvm_pte_table(ctx->old, ctx->level)) {
+		u64 end = ctx->addr + kvm_granule_size(ctx->level);
+
+		kvm_call_hyp(__kvm_tlb_flush_vmid_range, mmu, ctx->addr, end);
+	} else if (kvm_pte_valid(ctx->old)) {
 		kvm_call_hyp(__kvm_tlb_flush_vmid_ipa, mmu, ctx->addr, ctx->level);
+	}
 
 	if (stage2_pte_is_counted(ctx->old))
 		mm_ops->put_page(ctx->ptep);
-- 
2.40.1.698.g37aff9b760-goog