linux-kernel - Re: [PATCH v6 02/38] KVM: x86: hyper-v: Resurrect dedicated KVM_REQ_HV_TLB

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Message-ID: <420b6cfdeab348f93c0de20ef07b66663fe5030c.camel@redhat.com>
Date:   Tue, 07 Jun 2022 11:46:10 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Michael Kelley <mikelley@...rosoft.com>,
        Siddharth Chandrasekaran <sidcha@...zon.de>,
        Yuan Yao <yuan.yao@...ux.intel.com>,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 02/38] KVM: x86: hyper-v: Resurrect dedicated
 KVM_REQ_HV_TLB_FLUSH flag

On Mon, 2022-06-06 at 10:36 +0200, Vitaly Kuznetsov wrote:
> In preparation to implementing fine-grained Hyper-V TLB flush and
> L2 TLB flush, resurrect dedicated KVM_REQ_HV_TLB_FLUSH request bit.
> As
> KVM_REQ_TLB_FLUSH_GUEST/KVM_REQ_TLB_FLUSH_CURRENT are stronger
> operations,
> clear KVM_REQ_HV_TLB_FLUSH request in
> kvm_service_local_tlb_flush_requests()
> when any of these were also requested.
> 
> No (real) functional change intended.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
> ---
>  arch/x86/include/asm/kvm_host.h |  2 ++
>  arch/x86/kvm/hyperv.c           |  4 ++--
>  arch/x86/kvm/x86.c              | 10 ++++++++--
>  3 files changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h
> b/arch/x86/include/asm/kvm_host.h
> index 8699f715d867..7a6a6f47b603 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -108,6 +108,8 @@
>         KVM_ARCH_REQ_FLAGS(30, KVM_REQUEST_WAIT |
> KVM_REQUEST_NO_WAKEUP)
>  #define KVM_REQ_MMU_FREE_OBSOLETE_ROOTS \
>         KVM_ARCH_REQ_FLAGS(31, KVM_REQUEST_WAIT |
> KVM_REQUEST_NO_WAKEUP)
> +#define KVM_REQ_HV_TLB_FLUSH \
> +       KVM_ARCH_REQ_FLAGS(32, KVM_REQUEST_WAIT |
> KVM_REQUEST_NO_WAKEUP)
>  
>  #define
> CR0_RESERVED_BITS                                               \
>         (~(unsigned long)(X86_CR0_PE | X86_CR0_MP | X86_CR0_EM |
> X86_CR0_TS \
> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> index 46f9dfb60469..b402ad059eb9 100644
> --- a/arch/x86/kvm/hyperv.c
> +++ b/arch/x86/kvm/hyperv.c
> @@ -1876,11 +1876,11 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu
> *vcpu, struct kvm_hv_hcall *hc)
>          * analyze it here, flush TLB regardless of the specified
> address space.
>          */
>         if (all_cpus) {
> -               kvm_make_all_cpus_request(kvm,
> KVM_REQ_TLB_FLUSH_GUEST);
> +               kvm_make_all_cpus_request(kvm, KVM_REQ_HV_TLB_FLUSH);
>         } else {
>                 sparse_set_to_vcpu_mask(kvm, sparse_banks,
> valid_bank_mask, vcpu_mask);
>  
> -               kvm_make_vcpus_request_mask(kvm,
> KVM_REQ_TLB_FLUSH_GUEST, vcpu_mask);
> +               kvm_make_vcpus_request_mask(kvm,
> KVM_REQ_HV_TLB_FLUSH, vcpu_mask);
>         }
>  
>  ret_success:
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 67732e658e76..80cd3eb5e7de 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3353,11 +3353,17 @@ static inline void
> kvm_vcpu_flush_tlb_current(struct kvm_vcpu *vcpu)
>   */
>  void kvm_service_local_tlb_flush_requests(struct kvm_vcpu *vcpu)
>  {
> -       if (kvm_check_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu))
> +       if (kvm_check_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu)) {
>                 kvm_vcpu_flush_tlb_current(vcpu);
> +               kvm_clear_request(KVM_REQ_HV_TLB_FLUSH, vcpu);
> +       }
>  
> -       if (kvm_check_request(KVM_REQ_TLB_FLUSH_GUEST, vcpu))
> +       if (kvm_check_request(KVM_REQ_TLB_FLUSH_GUEST, vcpu)) {
> +               kvm_vcpu_flush_tlb_guest(vcpu);
> +               kvm_clear_request(KVM_REQ_HV_TLB_FLUSH, vcpu);
> +       } else if (kvm_check_request(KVM_REQ_HV_TLB_FLUSH, vcpu)) {
>                 kvm_vcpu_flush_tlb_guest(vcpu);
> +       }
>  }
>  EXPORT_SYMBOL_GPL(kvm_service_local_tlb_flush_requests);
>  

Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>

Best regards,
	Maxim Levitsky