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[142.68.128.5]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-46a3e64cf47sm146147721cf.3.2025.01.03.06.31.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 03 Jan 2025 06:31:39 -0800 (PST) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1tTiiA-00000000iUS-1wLH; Fri, 03 Jan 2025 10:31:38 -0400 Date: Fri, 3 Jan 2025 10:31:38 -0400 From: Jason Gunthorpe To: David Woodhouse Cc: Thomas Gleixner , Alex Williamson , kvm@vger.kernel.org, quic_bqiang@quicinc.com, kvalo@kernel.org, prestwoj@gmail.com, linux-wireless@vger.kernel.org, ath11k@lists.infradead.org, iommu@lists.linux.dev, kernel@quicinc.com, johannes@sipsolutions.net, jtornosm@redhat.com Subject: Re: [PATCH RFC/RFT] vfio/pci: Create feature to disable MSI virtualization Message-ID: <20250103143138.GC26854@ziepe.ca> References: <20240812170014.1583783-1-alex.williamson@redhat.com> <20240813163053.GK1985367@ziepe.ca> <87r0aspby6.ffs@tglx> <03fdfde8dc05ecce1f1edececf0800d8cb919ac1.camel@infradead.org> Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <03fdfde8dc05ecce1f1edececf0800d8cb919ac1.camel@infradead.org> On Fri, Dec 13, 2024 at 09:10:30AM +0000, David Woodhouse wrote: > > A: The guest OS just hands the device a standard MSI message encoding > the target guest APIC ID and vector (etc.), and the IOMMU does the > rest. Nothing 'intercedes' between the guest and the device to mess > with that MSI message. > /me wakes up... Well, I share your dream at least. :\ Have the VMM shadow the virtual interrupt remapping tables and assign it to the phyiscal remapping so that the physical addr/data pair doesn't change. Driving interrupt routing fully via the remapping HW and not via MSI interception. IIRC Alex had a patch series for qemu to capture and rewrite the ath non-standard MSI locations, so virtualization worries should not block moving ath to use the device-specific MSI.. Jason