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AFNElJ85amJhnN18vZTuFe79aZCUJnTDh+hVmzzMKJu2NTq4RpknIoXwdQZkWuEnAQ/iA30aVJ8=@vger.kernel.org X-Gm-Message-State: AOJu0YxbMLgdLjh83TzlMcveFarUuymjORzitBbIt01khmqHz3efnVYc 59LiYHSzoF+Dmm7phweLJn3Kr0iBmm/C3cmDN2Kg6X+CXvfBlu4cRbOSb1o/Bz969rvseqyELkt zu2Cn9A== X-Received: from plbf14.prod.google.com ([2002:a17:902:e98e:b0:2b2:470c:82e2]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:d510:b0:2b4:586d:2e5c with SMTP id d9443c01a7336-2b98b2842admr23964655ad.2.1777467533978; Wed, 29 Apr 2026 05:58:53 -0700 (PDT) Date: Wed, 29 Apr 2026 05:58:51 -0700 In-Reply-To: <0dacbe06-5b97-4dee-b8f2-a235b70448e2@intel.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260428070349.1633238-1-chenyi.qiang@intel.com> <3235eb76-9b28-4000-920a-491659927e67@redhat.com> <04c954e6-a23a-4cc8-8bd3-5882a951a8cc@intel.com> <0dacbe06-5b97-4dee-b8f2-a235b70448e2@intel.com> Message-ID: Subject: Re: [PATCH] KVM: VMX: Fall back to IRR scan when PIR is empty despite PID.ON being set From: Sean Christopherson To: Chenyi Qiang Cc: Paolo Bonzini , kvm@vger.kernel.org, Jim Mattson , Gao Chao , Farrah Chen Content-Type: text/plain; charset="us-ascii" On Wed, Apr 29, 2026, Chenyi Qiang wrote: > On 4/28/2026 11:50 PM, Sean Christopherson wrote: > > On Tue, Apr 28, 2026, Chenyi Qiang wrote: > >> On 4/28/2026 3:45 PM, Paolo Bonzini wrote: > >>> On 4/28/26 09:03, Chenyi Qiang wrote: > >>>> The interrupt is not lost (it resides in the IRR from the first sync and > >>>> is recovered on the next vcpu_enter_guest() iteration), but the incorrect > >>>> max_irr causes a spurious WARNING and a wasted L2 VM-Enter/VM-Exit cycle. > >>>> > >>>> Fixes: b41f8638b9d3 ("KVM: VMX: Isolate pure loads from atomic XCHG when processing PIR") > > > > Cc: stable@vger.kernel.org > > > >>>> Reported-by: Farrah Chen > >>>> Assisted-by: GitHub Copilot:Claude Opus 4.6 > >>>> Signed-off-by: Chenyi Qiang > >>>> > >>>> --- > >>>> There is a WARNING call trace during a nested VM stress test. > > > > Any chance the stress test is something that can be shared? I've seen this WARN > > 2-3 times over the last year, but it was never reproducible, and so intermittent > > that I couldn't even correlate what I was doing at the time with the WARN. > > It's not something special. The stress test is only to create and tear down > 20 nested VM instance in a cycle. It often takes more than 20 cycles to > reproduce this issue. Got it, thanks much!