linux-kernel - Re: [PATCH v7 02/12] KVM: arm64: Use kvm_arch_flush_remote

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Message-ID: <ZMgsjx8dwKd4xBGe@google.com>
Date:   Mon, 31 Jul 2023 14:50:07 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     Raghavendra Rao Ananta <rananta@...gle.com>,
        Oliver Upton <oliver.upton@...ux.dev>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Paolo Bonzini <pbonzini@...hat.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>,
        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: [PATCH v7 02/12] KVM: arm64: Use kvm_arch_flush_remote_tlbs()

On Thu, Jul 27, 2023, Marc Zyngier wrote:
> On Sat, 22 Jul 2023 03:22:41 +0100,
> Raghavendra Rao Ananta <rananta@...gle.com> wrote:
> > 
> > Stop depending on CONFIG_HAVE_KVM_ARCH_TLB_FLUSH_ALL and opt to
> > standardize on kvm_arch_flush_remote_tlbs() since it avoids
> > duplicating the generic TLB stats across architectures that implement
> > their own remote TLB flush.
> > 
> > This adds an extra function call to the ARM64 kvm_flush_remote_tlbs()
> > path, but that is a small cost in comparison to flushing remote TLBs.
> 
> Well, there is no such thing as a "remote TLB" anyway. We either have
> a non-shareable or inner-shareable invalidation. The notion of remote
> would imply that we track who potentially has a TLB, which we
> obviously don't.

Maybe kvm_arch_flush_vm_tlbs()?  The "remote" part is misleading even on x86 when
running on Hyper-V, as the flush may be done via a single hypercall and by kicking
"remote" vCPUs.