From: Wanpeng Li <kernellwp@gmail.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
kvm <kvm@vger.kernel.org>, "Radim Krčmář" <rkrcmar@redhat.com>,
"Wanpeng Li" <wanpeng.li@hotmail.com>
Subject: Re: [PATCH RESEND 3/3] KVM: Add flush_on_enter before guest enter
Date: Thu, 9 Nov 2017 20:31:00 +0800 [thread overview]
Message-ID: <CANRm+CxK_aA6vCWsn+66=cYA7ztkB9qppenfrbixCck5zTsQNA@mail.gmail.com> (raw)
In-Reply-To: <cc07b143-d3ae-4ce3-fe87-73f3b3a73451@redhat.com>
2017-11-09 18:54 GMT+08:00 Paolo Bonzini <pbonzini@redhat.com>:
> On 09/11/2017 03:02, Wanpeng Li wrote:
>> From: Wanpeng Li <wanpeng.li@hotmail.com>
>>
>> PV-Flush guest would indicate to flush on enter, flush the TLB before
>> entering and exiting the guest.
>>
>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>> Cc: Radim Krčmář <rkrcmar@redhat.com>
>> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
>> ---
>> arch/x86/kvm/x86.c | 12 ++++++++++--
>> 1 file changed, 10 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index 1ea28a2..f295360 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -2116,7 +2116,13 @@ static void record_steal_time(struct kvm_vcpu *vcpu)
>> &vcpu->arch.st.steal, sizeof(struct kvm_steal_time))))
>> return;
>>
>> - vcpu->arch.st.steal.preempted = KVM_VCPU_NOT_PREEMPTED;
>> + if (xchg(&vcpu->arch.st.steal.preempted, KVM_VCPU_NOT_PREEMPTED) ==
>> + (KVM_VCPU_SHOULD_FLUSH | KVM_VCPU_PREEMPTED))
>> + /*
>> + * Do TLB_FLUSH before entering the guest, its passed
>> + * the stage of request checking
>> + */
>> + kvm_x86_ops->tlb_flush(vcpu);
>>
>> if (vcpu->arch.st.steal.version & 1)
>> vcpu->arch.st.steal.version += 1; /* first time write, random junk */
>> @@ -2887,7 +2893,9 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu)
>> if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED))
>> return;
>>
>> - vcpu->arch.st.steal.preempted = KVM_VCPU_PREEMPTED;
>> + if (xchg(&vcpu->arch.st.steal.preempted, KVM_VCPU_PREEMPTED) ==
>> + KVM_VCPU_SHOULD_FLUSH)
>> + kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
>
> This is not necessary. Instead, you can just OR the KVM_VCPU_PREEMPTED
> bit; record_steal_time will pick up the request and do the TLB flush later.
>
> Also, I think this is a case where you should prefer INVVPID to INVEP.
> That's because "execution of the INVEPT instruction invalidates
> guest-physical mappings and combined mappings" while "execution of the
> INVVPID instruction invalidates linear mappings and combined mappings".
> In this case, invalidating guest-physical mapping is unnecessary.
>
> So you could add a new bool argument to kvm_x86_ops->tlb_flush. In
> vmx.c, __vmx_flush_tlb can do invept if "enable_ept && (invalidate_gpa
> || !enable_vpid)".
Agreed.
Regards,
Wanpeng Li
prev parent reply other threads:[~2017-11-09 12:31 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-09 2:02 [PATCH RESEND 0/3] KVM: Paravirt remote TLB flush Wanpeng Li
2017-11-09 2:02 ` [PATCH RESEND 1/3] KVM: Add vCPU running/preempted state Wanpeng Li
2017-11-09 2:02 ` [PATCH RESEND 2/3] KVM: Add paravirt remote TLB flush Wanpeng Li
2017-11-09 10:48 ` Paolo Bonzini
2017-11-09 11:01 ` Wanpeng Li
2017-11-09 11:02 ` Paolo Bonzini
2017-11-09 11:08 ` Wanpeng Li
2017-11-09 15:11 ` Radim Krčmář
2017-11-09 2:02 ` [PATCH RESEND 3/3] KVM: Add flush_on_enter before guest enter Wanpeng Li
2017-11-09 10:54 ` Paolo Bonzini
2017-11-09 12:31 ` Wanpeng Li [this message]
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