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From:   Vitaly Kuznetsov <vkuznets@redhat.com>
To:     Maxim Levitsky <mlevitsk@redhat.com>, kvm@vger.kernel.org,
        Paolo Bonzini <pbonzini@redhat.com>
Cc:     Sean Christopherson <seanjc@google.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Michael Kelley <mikelley@microsoft.com>,
        Siddharth Chandrasekaran <sidcha@amazon.de>,
        Yuan Yao <yuan.yao@linux.intel.com>,
        linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v6 05/38] KVM: x86: hyper-v: Handle
 HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST{,EX} calls gently
In-Reply-To: <0a7cada4844181d50b7ca971af5d8a4731171336.camel@redhat.com>
References: <20220606083655.2014609-1-vkuznets@redhat.com>
 <20220606083655.2014609-6-vkuznets@redhat.com>
 <0a7cada4844181d50b7ca971af5d8a4731171336.camel@redhat.com>
Date:   Mon, 13 Jun 2022 14:58:39 +0200
Message-ID: <87leu0k9ds.fsf@redhat.com>
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Maxim Levitsky <mlevitsk@redhat.com> writes:

...

>> =C2=A0
>> =C2=A0void kvm_hv_vcpu_flush_tlb(struct kvm_vcpu *vcpu)
>> =C2=A0{
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0struct kvm_vcpu_hv_tlb_f=
lush_fifo *tlb_flush_fifo;
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0struct kvm_vcpu_hv *hv_v=
cpu =3D to_hv_vcpu(vcpu);
>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0u64 entries[KVM_HV_TLB_FLUSH_=
FIFO_SIZE];
>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0int i, j, count;
>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0gva_t gva;
>> =C2=A0
>> -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0kvm_vcpu_flush_tlb_guest(vcpu=
);
>> -
>> -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0if (!hv_vcpu)
>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0if (!tdp_enabled || !hv_vcpu)=
 {
> I haven't noticed that in the review I did back then, but
> any reason why !tdp_enabled?

This follows the logic in kvm_vcpu_flush_tlb_guest():

	if (!tdp_enabled) {
		/*
		 * A TLB flush on behalf of the guest is equivalent to
		 * INVPCID(all), toggling CR4.PGE, etc., which requires
		 * a forced sync of the shadow page tables.  Ensure all the
		 * roots are synced and the guest TLB in hardware is clean.
		 */
		kvm_mmu_sync_roots(vcpu);
		kvm_mmu_sync_prev_roots(vcpu);
	}

and as !tdp_enabled should be a rare debug or special case I decided to
take the shortcut and not drag any of this logic into hyperv emulation
code.

--=20
Vitaly