linux-kernel - Re: [PATCH v8 03/14] KVM: arm64: Use kvm_arch_flush_remote

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Message-ID: <b91d1869-3a1d-d9eb-27b0-0aac94cca8e0@redhat.com>
Date:   Wed, 9 Aug 2023 14:10:12 +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>,
        Reiji Watanabe <reijiw@...gle.com>,
        Colton Lewis <coltonlewis@...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, Shaoqin Huang <shahuang@...hat.com>
Subject: Re: [PATCH v8 03/14] KVM: arm64: Use kvm_arch_flush_remote_tlbs()


On 8/9/23 09:13, Raghavendra Rao Ananta 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.
> 
> 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: Raghavendra Rao Ananta <rananta@...gle.com>
> Reviewed-by: Shaoqin Huang <shahuang@...hat.com>
> ---
>   arch/arm64/include/asm/kvm_host.h | 2 ++
>   arch/arm64/kvm/Kconfig            | 1 -
>   arch/arm64/kvm/mmu.c              | 6 +++---
>   3 files changed, 5 insertions(+), 4 deletions(-)
> 

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

> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 8b6096753740c..20f2ba149c70c 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -1111,6 +1111,8 @@ int __init kvm_set_ipa_limit(void);
>   #define __KVM_HAVE_ARCH_VM_ALLOC
>   struct kvm *kvm_arch_alloc_vm(void);
>   
> +#define __KVM_HAVE_ARCH_FLUSH_REMOTE_TLBS
> +
>   static inline bool kvm_vm_is_protected(struct kvm *kvm)
>   {
>   	return false;
> diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
> index f531da6b362e9..6b730fcfee379 100644
> --- a/arch/arm64/kvm/Kconfig
> +++ b/arch/arm64/kvm/Kconfig
> @@ -25,7 +25,6 @@ menuconfig KVM
>   	select MMU_NOTIFIER
>   	select PREEMPT_NOTIFIERS
>   	select HAVE_KVM_CPU_RELAX_INTERCEPT
> -	select HAVE_KVM_ARCH_TLB_FLUSH_ALL
>   	select KVM_MMIO
>   	select KVM_GENERIC_DIRTYLOG_READ_PROTECT
>   	select KVM_XFER_TO_GUEST_WORK
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 6db9ef288ec38..0ac721fa27f18 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -161,15 +161,15 @@ static bool memslot_is_logging(struct kvm_memory_slot *memslot)
>   }
>   
>   /**
> - * kvm_flush_remote_tlbs() - flush all VM TLB entries for v7/8
> + * kvm_arch_flush_remote_tlbs() - flush all VM TLB entries for v7/8
>    * @kvm:	pointer to kvm structure.
>    *
>    * Interface to HYP function to flush all VM TLB entries
>    */
> -void kvm_flush_remote_tlbs(struct kvm *kvm)
> +int kvm_arch_flush_remote_tlbs(struct kvm *kvm)
>   {
> -	++kvm->stat.generic.remote_tlb_flush_requests;
>   	kvm_call_hyp(__kvm_tlb_flush_vmid, &kvm->arch.mmu);
> +	return 0;
>   }
>   
>   static bool kvm_is_device_pfn(unsigned long pfn)