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Wed, 4 Nov 2020 12:40:19 +0000 Date: Wed, 4 Nov 2020 08:40:17 -0400 From: Jason Gunthorpe To: "Tian, Kevin" CC: "Jiang, Dave" , Bjorn Helgaas , "vkoul@kernel.org" , "Dey, Megha" , "maz@kernel.org" , "bhelgaas@google.com" , "tglx@linutronix.de" , "alex.williamson@redhat.com" , "Pan, Jacob jun" , "Raj, Ashok" , "Liu, Yi L" , "Lu, Baolu" , "Kumar, Sanjay K" , "Luck, Tony" , "jing.lin@intel.com" , "Williams, Dan J" , "kwankhede@nvidia.com" , "eric.auger@redhat.com" , "parav@mellanox.com" , "rafael@kernel.org" , "netanelg@mellanox.com" , "shahafs@mellanox.com" , "yan.y.zhao@linux.intel.com" , "pbonzini@redhat.com" , "Ortiz, Samuel" , "Hossain, Mona" , "dmaengine@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-pci@vger.kernel.org" , "kvm@vger.kernel.org" Subject: Re: [PATCH v4 06/17] PCI: add SIOV and IMS capability detection Message-ID: <20201104124017.GW2620339@nvidia.com> References: <20201030195159.GA589138@bjorn-Precision-5520> <71da5f66-e929-bab1-a1c6-a9ac9627a141@intel.com> <20201030224534.GN2620339@nvidia.com> <20201102132158.GA3352700@nvidia.com> <20201103124351.GM2620339@nvidia.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: MN2PR22CA0003.namprd22.prod.outlook.com (2603:10b6:208:238::8) To DM6PR12MB3834.namprd12.prod.outlook.com (2603:10b6:5:14a::12) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from mlx.ziepe.ca (156.34.48.30) by MN2PR22CA0003.namprd22.prod.outlook.com (2603:10b6:208:238::8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3499.18 via Frontend Transport; Wed, 4 Nov 2020 12:40:18 +0000 Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1kaI5J-00GU44-LN; Wed, 04 Nov 2020 08:40:17 -0400 X-LD-Processed: 43083d15-7273-40c1-b7db-39efd9ccc17a,ExtAddr DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1604493629; bh=ly2oeyLHt+9xgCf6InlNFupONQhHnN+seyBdY1snqFM=; h=ARC-Seal:ARC-Message-Signature:ARC-Authentication-Results:Date: From:To:CC:Subject:Message-ID:References:Content-Type: Content-Disposition:In-Reply-To:X-ClientProxiedBy:MIME-Version: X-MS-Exchange-MessageSentRepresentingType:X-LD-Processed; b=Fodb48BRizFtyLLl2nCM6FAknIzBy0v3MMHEJlFDmeQJ7Rtru0ycAtDwJX/1RS688 H3EQrsy4oQQtO9OPvoO230V97TPEYgWwHlr2PMnDcXCD6Z8XvsALcnuMh6hWKm1YgO Wa/lad7AY3njLf81mp1fVFjaJ6BjucLUhowWxGAaxyZLJzVDj1QjlQTN65ZTQeYILP JCZmC92zcdbMXDxpeZB6I6k/5SRBBSNtVX10O6lPLizqit+kMBx+NUtZYFzCwCkkXO VFxuEOHN/l3lSa8SWiVsyzV9kO6V4X0blymDK65UmdUoPGKfTw5DelnufLrUfeV0na CHmR8JyLD9/RA== Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 04, 2020 at 03:41:33AM +0000, Tian, Kevin wrote: > > From: Jason Gunthorpe > > Sent: Tuesday, November 3, 2020 8:44 PM > > > > On Tue, Nov 03, 2020 at 02:49:27AM +0000, Tian, Kevin wrote: > > > > > > There is a missing hypercall to allow the guest to do this on its own, > > > > presumably it will someday be fixed so IMS can work in guests. > > > > > > Hypercall is VMM specific, while IMS cap provides a VMM-agnostic > > > interface so any guest driver (if following the spec) can seamlessly > > > work on all hypervisors. > > > > It is a *VMM* issue, not PCI. Adding a PCI cap to describe a VMM issue > > is architecturally wrong. > > > > IMS *can not work* in any hypervsior without some special > > hypercall. Just block it in the platform code and forget about the PCI > > cap. > > > > It's per-device thing instead of platform thing. If the VMM understands > the IMS format of a specific device and virtualize it to the guest, Please no! Adding device specific emulation is just going down deeper into this bad architecture. Interrupts is a platform issue. Using emulation of MSI to dynamically insert vectors to a VM was a reasonable, but hacky thing. Now it needs proper platform support. Jason