linux-kernel - Re: [PATCH v4 02/37] KVM: x86: hyper-v: Resurrect dedicated KVM_REQ_HV_TLB

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Date:   Fri, 27 May 2022 11:00:11 +0800
From:   Yuan Yao <yuan.yao@...ux.intel.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Michael Kelley <mikelley@...rosoft.com>,
        Siddharth Chandrasekaran <sidcha@...zon.de>,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 02/37] KVM: x86: hyper-v: Resurrect dedicated
 KVM_REQ_HV_TLB_FLUSH flag

On Wed, May 25, 2022 at 11:00:58AM +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_GUEST/KVM_REQ_TLB_FLUSH_CURRENT

Duplicated KVM_REQ_TLB_FLUSH_GUEST here ?

> 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 151880cfab9e..92509ee6ae1b 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -105,6 +105,8 @@
>  	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 891507b2eca5..f98503431f8d 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3363,11 +3363,17 @@ 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);
>
> --
> 2.35.3
>