linux-kernel - Re: [PATCH v2 18/31] KVM: nSVM: hyper-v: Direct TLB flush

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Date:   Thu, 7 Apr 2022 18:50:29 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Michael Kelley <mikelley@...rosoft.com>,
        Siddharth Chandrasekaran <sidcha@...zon.de>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 18/31] KVM: nSVM: hyper-v: Direct TLB flush

On Thu, Apr 07, 2022, Vitaly Kuznetsov wrote:
> @@ -486,6 +487,17 @@ static void nested_save_pending_event_to_vmcb12(struct vcpu_svm *svm,
>  
>  static void nested_svm_transition_tlb_flush(struct kvm_vcpu *vcpu)
>  {
> +	/*
> +	 * KVM_REQ_HV_TLB_FLUSH flushes entries from either L1's VPID or

Can you use VP_ID or some variation to avoid "VPID"?  This looks like a copy+paste
from nVMX gone bad and will confuse the heck out of people that are more familiar
with VMX's VPID.

> +	 * L2's VPID upon request from the guest. Make sure we check for
> +	 * pending entries for the case when the request got misplaced (e.g.
> +	 * a transition from L2->L1 happened while processing Direct TLB flush
> +	 * request or vice versa). kvm_hv_vcpu_flush_tlb() will not flush
> +	 * anything if there are no requests in the corresponding buffer.
> +	 */
> +	if (to_hv_vcpu(vcpu))
> +		kvm_make_request(KVM_REQ_HV_TLB_FLUSH, vcpu);
> +
>  	/*
>  	 * TODO: optimize unconditional TLB flush/MMU sync.  A partial list of
>  	 * things to fix before this can be conditional: