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Date:   Mon, 17 Jul 2023 10:12:57 +0200
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Subject: Re: [PATCH v6 02/11] KVM: arm64: Use kvm_arch_flush_remote_tlbs()
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To:     Raghavendra Rao Ananta <rananta@google.com>,
        Oliver Upton <oliver.upton@linux.dev>,
        Marc Zyngier <maz@kernel.org>,
        James Morse <james.morse@arm.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>
Cc:     Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <seanjc@google.com>,
        Huacai Chen <chenhuacai@kernel.org>,
        Zenghui Yu <yuzenghui@huawei.com>,
        Anup Patel <anup@brainfault.org>,
        Atish Patra <atishp@atishpatra.org>,
        Jing Zhang <jingzhangos@google.com>,
        Colton Lewis <coltonlewis@google.com>,
        David Matlack <dmatlack@google.com>,
        linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev,
        linux-mips@vger.kernel.org, kvm-riscv@lists.infradead.org,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org, Zenghui Yu <zenghui.yu@linux.dev>,
        Gavin Shan <gshan@redhat.com>
References: <20230715005405.3689586-1-rananta@google.com>
 <20230715005405.3689586-3-rananta@google.com>
From:   =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= <philmd@linaro.org>
In-Reply-To: <20230715005405.3689586-3-rananta@google.com>
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Hi Raghavendra, David,

On 15/7/23 02:53, Raghavendra Rao Ananta wrote:
> From: David Matlack <dmatlack@google.com>
> 
> Use kvm_arch_flush_remote_tlbs() instead of
> CONFIG_HAVE_KVM_ARCH_TLB_FLUSH_ALL. The two mechanisms solve the same
> problem, allowing architecture-specific code to provide a non-IPI
> implementation of remote TLB flushing.
> 
> Dropping CONFIG_HAVE_KVM_ARCH_TLB_FLUSH_ALL allows KVM to standardize
> all architectures on kvm_arch_flush_remote_tlbs() instead of maintaining
> two mechanisms.
> 
> 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.
> 
> In addition, instead of just incrementing remote_tlb_flush_requests
> stat, the generic interface would also increment the
> remote_tlb_flush stat.
> 
> Signed-off-by: David Matlack <dmatlack@google.com>
> Signed-off-by: Raghavendra Rao Ananta <rananta@google.com>
> Reviewed-by: Zenghui Yu <zenghui.yu@linux.dev>
> Acked-by: Oliver Upton <oliver.upton@linux.dev>
> Reviewed-by: Gavin Shan <gshan@redhat.com>
> ---
>   arch/arm64/include/asm/kvm_host.h | 3 +++
>   arch/arm64/kvm/Kconfig            | 1 -
>   arch/arm64/kvm/mmu.c              | 6 +++---
>   virt/kvm/Kconfig                  | 3 ---
>   virt/kvm/kvm_main.c               | 2 --
>   5 files changed, 6 insertions(+), 9 deletions(-)

You are doing 2 changes in the same patch:

- Have ARM use kvm_arch_flush_remote_tlbs() instead of
   HAVE_KVM_ARCH_TLB_FLUSH_ALL,
- Drop the now unused HAVE_KVM_ARCH_TLB_FLUSH_ALL.

Commits should be atomic, to allow partial
revert or cherry-pick.

Preferably splitting this patch in 2:
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>

Regards,

Phil.