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[2001:14ba:7262:6300:31d3:dad0:4a4b:3d13]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5389fd5df91sm1912604e87.82.2024.10.02.05.43.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Oct 2024 05:43:50 -0700 (PDT) From: =?UTF-8?q?Markku=20Ahvenj=C3=A4rvi?= To: seanjc@google.com Cc: bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, janne.karhunen@gmail.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, mankku@gmail.com, mingo@redhat.com, pbonzini@redhat.com, tglx@linutronix.de, x86@kernel.org Subject: Re: [PATCH 1/1] KVM: nVMX: update VPPR on vmlaunch/vmresume Date: Wed, 2 Oct 2024 15:42:56 +0300 Message-ID: <20241002124324.14360-1-mankku@gmail.com> X-Mailer: git-send-email 2.44.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Sean, > On Fri, Sep 20, 2024, Markku Ahvenjärvi wrote: > > Running certain hypervisors under KVM on VMX suffered L1 hangs after > > launching a nested guest. The external interrupts were not processed on > > vmlaunch/vmresume due to stale VPPR, and L2 guest would resume without > > allowing L1 hypervisor to process the events. > > > > The patch ensures VPPR to be updated when checking for pending > > interrupts. > > This is architecturally incorrect, PPR isn't refreshed at VM-Enter. I looked into this and found the following from Intel manual: "30.1.3 PPR Virtualization The processor performs PPR virtualization in response to the following operations: (1) VM entry; (2) TPR virtualization; and (3) EOI virtualization. ..." The section "27.3.2.5 Updating Non-Register State" further explains the VM enter: "If the “virtual-interrupt delivery” VM-execution control is 1, VM entry loads the values of RVI and SVI from the guest interrupt-status field in the VMCS (see Section 25.4.2). After doing so, the logical processor first causes PPR virtualization (Section 30.1.3) and then evaluates pending virtual interrupts (Section 30.2.1). If a virtual interrupt is recognized, it may be delivered in VMX non-root operation immediately after VM entry (including any specified event injection) completes; ..." According to that, PPR is supposed to be refreshed at VM-Enter, or am I missing something here? Kind regards, Markku