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AJvYcCU1340Azt3wORl4WcV5qL0qZbY4eE2h0kgTyCrgJmPxuzZEXzrTt7H1WmxfD60npCW/rrRDx52580pn30s=@vger.kernel.org X-Gm-Message-State: AOJu0YysL5O5NYLFydaB9F5ey6wOj38M0WaLznAAfNn6Q+8FJAxvWlUz gjPIbtcS8xnuAxikg9S9iYSWK9U94iWUZ0rohA02dNjyZTTO5g8/NNdK9PTS2mn44Ug6CUElO+K Hpg== X-Google-Smtp-Source: AGHT+IF09wFzorMUM4Gi7oaYBSS+7g0HTnWRlVNYWepX7kLirX/lzxgzzddN7SGhZH0LCUn3aRIezx8SRCU= X-Received: from pjbsc7.prod.google.com ([2002:a17:90b:5107:b0:2ff:5fee:5e17]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:c949:b0:220:da88:2009 with SMTP id d9443c01a7336-22780e23fcfmr60355015ad.45.1742589889236; Fri, 21 Mar 2025 13:44:49 -0700 (PDT) Date: Fri, 21 Mar 2025 13:44:47 -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: <20250320142022.766201-1-seanjc@google.com> <20250320142022.766201-4-seanjc@google.com> Message-ID: Subject: Re: [PATCH v2 3/3] KVM: x86: Add a module param to control and enumerate device posted IRQs From: Sean Christopherson To: Chao Gao Cc: Paolo Bonzini , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Yosry Ahmed Content-Type: text/plain; charset="us-ascii" On Fri, Mar 21, 2025, Chao Gao wrote: > On Thu, Mar 20, 2025 at 10:59:19AM -0700, Sean Christopherson wrote: > >@@ -9776,8 +9777,8 @@ int kvm_x86_vendor_init(struct kvm_x86_init_ops *ops) > > if (r != 0) > > goto out_mmu_exit; > > > >- enable_device_posted_irqs &= enable_apicv && > >- irq_remapping_cap(IRQ_POSTING_CAP); > >+ enable_device_posted_irqs = allow_device_posted_irqs && enable_apicv && > >+ irq_remapping_cap(IRQ_POSTING_CAP); > > Can we simply drop this ... > > > > > kvm_ops_update(ops); > > > >@@ -14033,6 +14034,8 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_rmp_fault); > > > > static int __init kvm_x86_init(void) > > { > >+ allow_device_posted_irqs = enable_device_posted_irqs; > >+ > > kvm_init_xstate_sizes(); > > > > kvm_mmu_x86_module_init(); > > > > > >Option #2 is to shove the module param into vendor code, but leave the variable > >in kvm.ko, like we do for enable_apicv. > > > >I'm leaning toward option #2, as it's more flexible, arguably more intuitive, and > >doesn't prevent putting the logic in kvm_x86_vendor_init(). > > > > and do > > bool kvm_arch_has_irq_bypass(void) > { > return enable_device_posted_irqs && enable_apicv && > irq_remapping_cap(IRQ_POSTING_CAP); > } That would avoid the vendor module issues, but it would result in allow_device_posted_irqs not reflecting the state of KVM. We could partially address that by having the variable incorporate irq_remapping_cap(IRQ_POSTING_CAP) but not enable_apicv, but that's still a bit funky. Given that enable_apicv already has the "variable in kvm.ko, module param in kvm-{amd,intel}.ko" behavior, and that I am planning on giving enable_ipiv the same treatment (long story), my strong vote is to go with option #2 as it's the most flexibile, most accurate, and consistent with existing knobs.