linux-kernel - Re: [PATCH v3 15/34] KVM: x86: hyper-v: Introduce kvm_hv_is_tlb_flush

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Date:   Wed, 11 May 2022 14:25:33 +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>,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 15/34] KVM: x86: hyper-v: Introduce
 kvm_hv_is_tlb_flush_hcall()

On Thu, 2022-04-14 at 15:19 +0200, Vitaly Kuznetsov wrote:
> The newly introduced helper checks whether vCPU is performing a
> Hyper-V TLB flush hypercall. This is required to filter out L2 TLB
> flush hypercalls for processing.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
> ---
>  arch/x86/kvm/hyperv.h | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h
> index d59f96700104..ca67c18cef2c 100644
> --- a/arch/x86/kvm/hyperv.h
> +++ b/arch/x86/kvm/hyperv.h
> @@ -170,6 +170,24 @@ static inline void kvm_hv_vcpu_empty_flush_tlb(struct kvm_vcpu *vcpu)
>  	tlb_flush_ring = kvm_hv_get_tlb_flush_ring(vcpu);
>  	tlb_flush_ring->read_idx = tlb_flush_ring->write_idx;
>  }
> +
> +static inline bool kvm_hv_is_tlb_flush_hcall(struct kvm_vcpu *vcpu)
> +{
> +	struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
> +	u16 code;
> +
> +	if (!hv_vcpu)
> +		return false;
> +
> +	code = is_64_bit_hypercall(vcpu) ? kvm_rcx_read(vcpu) :
> +		kvm_rax_read(vcpu);
> +
> +	return (code == HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE ||
> +		code == HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST ||
> +		code == HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX ||
> +		code == HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST_EX);
> +}
> +
>  void kvm_hv_vcpu_flush_tlb(struct kvm_vcpu *vcpu);
>  
>  

Looks Ok, but my knowelege of HV spec is limited so I might have missed something.

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

Best regards,
	Maxim Levitsky