linux-kernel - Re: [RESEND PATCH v5 10/11] KVM: arm64: Invalidate the table entries upon a range

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Date:   Wed, 5 Jul 2023 10:51:18 +1000
From:   Gavin Shan <gshan@...hat.com>
To:     Raghavendra Rao Ananta <rananta@...gle.com>,
        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>,
        Colton Lewis <coltonlewis@...gle.com>,
        David Matlack <dmatlack@...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
Subject: Re: [RESEND PATCH v5 10/11] KVM: arm64: Invalidate the table entries
 upon a range


On 6/22/23 03:50, Raghavendra Rao Ananta wrote:
> 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>
> ---
>   arch/arm64/kvm/hyp/pgtable.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 

Reviewed-by: Gavin Shan <gshan@...hat.com>

> diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
> index df8ac14d9d3d4..50ef7623c54db 100644
> --- a/arch/arm64/kvm/hyp/pgtable.c
> +++ b/arch/arm64/kvm/hyp/pgtable.c
> @@ -766,7 +766,8 @@ static bool stage2_try_break_pte(const struct kvm_pgtable_visit_ctx *ctx,
>   	 * 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);
>