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[142.68.80.239]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7a4c7e0ddfasm379556485a.126.2024.08.13.16.16.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 13 Aug 2024 16:16:43 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.95) (envelope-from ) id 1se0ks-00AITY-S3; Tue, 13 Aug 2024 20:16:42 -0300 Date: Tue, 13 Aug 2024 20:16:42 -0300 From: Jason Gunthorpe To: Alex Williamson Cc: Thomas Gleixner , kvm@vger.kernel.org, quic_bqiang@quicinc.com, kvalo@kernel.org, prestwoj@gmail.com, linux-wireless@vger.kernel.org, ath11k@lists.infradead.org, dwmw2@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: <20240813231642.GR1985367@ziepe.ca> References: <20240812170014.1583783-1-alex.williamson@redhat.com> <20240813163053.GK1985367@ziepe.ca> <20240813151401.789c578f.alex.williamson@redhat.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240813151401.789c578f.alex.williamson@redhat.com> On Tue, Aug 13, 2024 at 03:14:01PM -0600, Alex Williamson wrote: > > Personally, I very much dislike this. Encouraging such hacky driver > > use of the interrupt subsystem is not a good direction. Enabling this > > in VMs will further complicate fixing the IRQ usages in these drivers > > over the long run. > > Clearly these _guest_ drivers are doing this regardless of the > interfaces provided by vfio, so I don't see how we're encouraging hacky > driver behavior, especially when it comes to Windows guest drivers. Because people will then say the Linux driver can't be fixed to properly use an irq_domain/etc as the only option that works in VMs will be the hacky copy from MSI-X approach :\ > > Thomas Gleixner has done alot of great work recently to clean this up. > > > > So if you imagine the driver is fixed, then this is not necessary. > > How so? Because if the driver is properly using the new irq_domain/etc infrastructure to model its additional interrupt source then this patch won't make it work in the VM anyhow, so it is not necessary.. Your other patch would be the only short term answer. Jason