From: Paolo Bonzini <pbonzini@redhat.com>
To: Joao Martins <joao.m.martins@oracle.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
"Radim Krčmář" <rkrcmar@redhat.com>,
"Sean Christopherson" <sean.j.christopherson@intel.com>,
"Vitaly Kuznetsov" <vkuznets@redhat.com>,
"Wanpeng Li" <wanpengli@tencent.com>,
"Jim Mattson" <jmattson@google.com>,
"Joerg Roedel" <joro@8bytes.org>,
"Liran Alon" <liran.alon@oracle.com>,
"Jag Raman" <jag.raman@oracle.com>
Subject: Re: [PATCH v1 1/3] KVM: VMX: Consider PID.PIR to determine if vCPU has pending interrupts
Date: Mon, 11 Nov 2019 16:58:33 +0100 [thread overview]
Message-ID: <5ee4c4ae-9d22-d560-bb61-e5f40b56da2e@redhat.com> (raw)
In-Reply-To: <030dd147-8c4f-d6e3-85a8-ee743ce4d5b0@oracle.com>
On 11/11/19 15:59, Joao Martins wrote:
>> Should we check the bitmap only if SN is false?
^^^^^
Of course it should be skipped if SN is false, as you correctly say below.
>> We have a precondition
>> that if SN is clear then non-empty PIR implies ON=1 (modulo the small
>> window in vmx_vcpu_pi_load of course), so that'd be a bit faster.
> Makes sense;
>
> The bitmap check was really meant for SN=1.
>
> Should SN=0 we would be saving ~22-27 cycles as far as I micro-benchmarked a few
> weeks ago. Now that you suggest it, it would be also good for older platforms too.
Or even newer platforms if they don't use VT-d.
Paolo
next prev parent reply other threads:[~2019-11-11 15:58 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-06 17:55 [PATCH v1 0/3] KVM: VMX: Posted Interrupts fixes Joao Martins
2019-11-06 17:56 ` [PATCH v1 1/3] KVM: VMX: Consider PID.PIR to determine if vCPU has pending interrupts Joao Martins
2019-11-07 16:00 ` Jag Raman
2019-11-11 14:46 ` Paolo Bonzini
2019-11-11 14:59 ` Joao Martins
2019-11-11 15:58 ` Paolo Bonzini [this message]
2019-11-06 17:56 ` [PATCH v1 2/3] KVM: VMX: Do not change PID.NDST when loading a blocked vCPU Joao Martins
2019-11-06 21:54 ` Joao Martins
2019-11-11 14:39 ` Paolo Bonzini
2019-11-11 14:48 ` Joao Martins
2019-11-11 14:50 ` Paolo Bonzini
2019-11-11 14:56 ` Joao Martins
2019-11-11 14:59 ` Liran Alon
2019-11-11 15:53 ` Sean Christopherson
2019-11-11 17:27 ` Joao Martins
2019-11-06 17:56 ` [PATCH v1 3/3] KVM: VMX: Introduce pi_is_pir_empty() helper Joao Martins
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