linux-kernel - Re: [PATCH v6 02/11] KVM: arm64: Use kvm_arch_flush_remote

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Message-ID: <0e5dd611-b047-5565-cf09-ad8844386b81@redhat.com>
Date:   Mon, 17 Jul 2023 19:27:29 +0800
From:   Shaoqin Huang <shahuang@...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, Zenghui Yu <zenghui.yu@...ux.dev>,
        Gavin Shan <gshan@...hat.com>
Subject: Re: [PATCH v6 02/11] KVM: arm64: Use kvm_arch_flush_remote_tlbs()



On 7/15/23 08:53, Raghavendra Rao Ananta wrote:
> From: David Matlack <dmatlack@...gle.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@...gle.com>
> Signed-off-by: Raghavendra Rao Ananta <rananta@...gle.com>
> Reviewed-by: Zenghui Yu <zenghui.yu@...ux.dev>
> Acked-by: Oliver Upton <oliver.upton@...ux.dev>
> Reviewed-by: Gavin Shan <gshan@...hat.com>
Reviewed-by: Shaoqin Huang <shahuang@...hat.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(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 8b6096753740..7281222f24ef 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -1111,6 +1111,9 @@ 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
> +int kvm_arch_flush_remote_tlbs(struct kvm *kvm);
> +
>   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 f531da6b362e..6b730fcfee37 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 6db9ef288ec3..0ac721fa27f1 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)
> diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
> index b74916de5183..484d0873061c 100644
> --- a/virt/kvm/Kconfig
> +++ b/virt/kvm/Kconfig
> @@ -62,9 +62,6 @@ config HAVE_KVM_CPU_RELAX_INTERCEPT
>   config KVM_VFIO
>          bool
>   
> -config HAVE_KVM_ARCH_TLB_FLUSH_ALL
> -       bool
> -
>   config HAVE_KVM_INVALID_WAKEUPS
>          bool
>   
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 70e5479797ac..d6b050786155 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -345,7 +345,6 @@ bool kvm_make_all_cpus_request(struct kvm *kvm, unsigned int req)
>   }
>   EXPORT_SYMBOL_GPL(kvm_make_all_cpus_request);
>   
> -#ifndef CONFIG_HAVE_KVM_ARCH_TLB_FLUSH_ALL
>   void kvm_flush_remote_tlbs(struct kvm *kvm)
>   {
>   	++kvm->stat.generic.remote_tlb_flush_requests;
> @@ -366,7 +365,6 @@ void kvm_flush_remote_tlbs(struct kvm *kvm)
>   		++kvm->stat.generic.remote_tlb_flush;
>   }
>   EXPORT_SYMBOL_GPL(kvm_flush_remote_tlbs);
> -#endif
>   
>   static void kvm_flush_shadow_all(struct kvm *kvm)
>   {

-- 
Shaoqin