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Tsirkin" To: Jason Gunthorpe Subject: Re: Virtio-IOMMU interrupt remapping design Message-ID: <20250617154331-mutt-send-email-mst@kernel.org> References: <> <20250616132031.GB1354058@ziepe.ca> MIME-Version: 1.0 In-Reply-To: <20250616132031.GB1354058@ziepe.ca> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: nLDlZRlVfcDTaxZyYHcbnU0pGxZiVjKZUhDC4bGQ1oc_1750189464 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Message-ID-Hash: TA4UU7C7NV6TNBQZMTOKNK7FPIPKPHBA X-Message-ID-Hash: TA4UU7C7NV6TNBQZMTOKNK7FPIPKPHBA X-MailFrom: mst@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; header-match-devel.spectrum-os.org-0; header-match-devel.spectrum-os.org-1; header-match-devel.spectrum-os.org-2; header-match-devel.spectrum-os.org-3; header-match-devel.spectrum-os.org-4; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: Demi Marie Obenour , Jason Wang , Xuan Zhuo , Eugenio =?iso-8859-1?Q?P=E9rez?= , "Rafael J. Wysocki" , Len Brown , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Joerg Roedel , Will Deacon , Robin Murphy , Alyssa Ross , virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, iommu@lists.linux.dev, x86@kernel.org, Spectrum OS Development X-Mailman-Version: 3.3.9 Precedence: list List-Id: Patches and low-level development discussion Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On Mon, Jun 16, 2025 at 10:20:31AM -0300, Jason Gunthorpe wrote: > On Sun, Jun 15, 2025 at 02:47:15PM -0400, Demi Marie Obenour wrote: > > > Is a paravirtualized IOMMU with interrupt remapping something that makes > > sense? > > IMHO linking interrupt remapping to the iommu is a poor design, > interrupt routing belongs in the irq subsystem, not in the iommu. > > The fact AMD and Intel both coupled their interrupt routing to their > iommu hardware is just a weird design decision. ARM didn't do this, > for instance. why does it matter in which device it resides? Way I see it, there is little reason to remap interrupts without also using an iommu, so why not a single device. what did I miss? > So I would not try to do this at all, you should have a > para-virtualized IRQ interface, not an extension to virtio-iommu > adding interrupt handling. :\ > > AFAIK hyperv shows how to build something like this. > > Jason