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AJvYcCVS+0U5n1OisVvU4lveHUrndG6txlmdiXvJSbnrQtTjzYjvoGAscpHRs0EE7fqleD5swUfCixv91mQG8AA=@vger.kernel.org X-Gm-Message-State: AOJu0YxK/RAcTtPaR4dt6er+Fyw7nu85uZMbqf5Bgtg/wuRgo9QJ5OnN FhR4Q/ou7NAxMyoWdEXPSRpqJ/qJ0s/e9gIP4cjqJgYXh2WzvvzcFKOmx1c+eLNorTRiAobcfS2 MQA== X-Google-Smtp-Source: AGHT+IFyxCzl6htX/DS8ClLuQoR7pJ/TqB4Bmf2NEvfb9DmOqq4wCNxnwjdldtCmTRsZzd2uBHMx+RmD5A4= X-Received: from pggs1.prod.google.com ([2002:a63:dc01:0:b0:af2:50f0:bc79]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a21:32a2:b0:1f5:7007:9eb7 with SMTP id adf61e73a8af0-20179983274mr4861364637.37.1744381968654; Fri, 11 Apr 2025 07:32:48 -0700 (PDT) Date: Fri, 11 Apr 2025 07:32:47 -0700 In-Reply-To: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250404193923.1413163-1-seanjc@google.com> <20250404193923.1413163-10-seanjc@google.com> Message-ID: Subject: Re: [PATCH 09/67] KVM: SVM: Track per-vCPU IRTEs using kvm_kernel_irqfd structure From: Sean Christopherson To: Sairaj Arun Kodilkar Cc: Paolo Bonzini , Joerg Roedel , David Woodhouse , Lu Baolu , kvm@vger.kernel.org, iommu@lists.linux.dev, linux-kernel@vger.kernel.org, Maxim Levitsky , Joao Martins , David Matlack Content-Type: text/plain; charset="us-ascii" On Fri, Apr 11, 2025, Arun Kodilkar, Sairaj wrote: > On 4/5/2025 1:08 AM, Sean Christopherson wrote: > > diff --git a/include/linux/kvm_irqfd.h b/include/linux/kvm_irqfd.h > > index 8ad43692e3bb..6510a48e62aa 100644 > > --- a/include/linux/kvm_irqfd.h > > +++ b/include/linux/kvm_irqfd.h > > @@ -59,6 +59,9 @@ struct kvm_kernel_irqfd { > > struct work_struct shutdown; > > struct irq_bypass_consumer consumer; > > struct irq_bypass_producer *producer; > > + > > + struct list_head vcpu_list; > > + void *irq_bypass_data; > > }; > > #endif /* __LINUX_KVM_IRQFD_H */ > > Hi Sean, > You missed to update the functions avic_set_pi_irte_mode and > avic_update_iommu_vcpu_affinity, which iterate over the ir_list. Well bugger, I did indeed. And now I'm questioning my (hacky) testing, as I don't see how avic_update_iommu_vcpu_affinity() survived. Oh, wow. This is disgustingly hilarious. By dumb luck, the offset of the data pointer relative to the list_head structure is the same in amd_svm_iommu_ir and kvm_kernel_irqfd. And the usage in avic_set_pi_irte_mode() and avic_update_iommu_vcpu_affinity() only ever touches the data, not "svm". So even though the structure is completely wrong, the math works out and avic_set_pi_irte_mode() and avic_update_iommu_vcpu_affinity() unknowingly pass in irq_bypass_data, and all is well. struct amd_svm_iommu_ir { struct list_head node; /* Used by SVM for per-vcpu ir_list */ void *data; /* Storing pointer to struct amd_ir_data */ struct vcpu_svm *svm; }; struct kvm_kernel_irqfd { ... struct kvm_vcpu *irq_bypass_vcpu; struct list_head vcpu_list; void *irq_bypass_data; }; Great catch! And thanks for the reviews!