linux-kernel - [PATCH v9 13/14] KVM: arm64: Invalidate the table entries upon a range

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Date:   Fri, 11 Aug 2023 04:51:26 +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:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Huacai Chen <chenhuacai@...nel.org>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Anup Patel <anup@...infault.org>,
        Atish Patra <atishp@...shpatra.org>,
        Jing Zhang <jingzhangos@...gle.com>,
        Reiji Watanabe <reijiw@...gle.com>,
        Colton Lewis <coltonlewis@...gle.com>,
        Raghavendra Rao Anata <rananta@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Fuad Tabba <tabba@...gle.com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        linux-mips@...r.kernel.org, kvm-riscv@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, Gavin Shan <gshan@...hat.com>,
        Shaoqin Huang <shahuang@...hat.com>
Subject: [PATCH v9 13/14] 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, leverage 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>
Reviewed-by: Gavin Shan <gshan@...hat.com>
Reviewed-by: Shaoqin Huang <shahuang@...hat.com>
---
 arch/arm64/kvm/hyp/pgtable.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index 5d14d5d5819a1..5ef098af17362 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -806,7 +806,8 @@ static bool stage2_try_break_pte(const struct kvm_pgtable_visit_ctx *ctx,
 		 * evicted pte value (if any).
 		 */
 		if (kvm_pte_table(ctx->old, ctx->level))
-			kvm_call_hyp(__kvm_tlb_flush_vmid, mmu);
+			kvm_tlb_flush_vmid_range(mmu, ctx->addr,
+						kvm_granule_size(ctx->level));
 		else if (kvm_pte_valid(ctx->old))
 			kvm_call_hyp(__kvm_tlb_flush_vmid_ipa, mmu,
 				     ctx->addr, ctx->level);
-- 
2.41.0.640.ga95def55d0-goog