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Wed, 18 Jun 2025 11:43:40 +0000 Received: from CH3PR12MB8659.namprd12.prod.outlook.com ([fe80::6eb6:7d37:7b4b:1732]) by CH3PR12MB8659.namprd12.prod.outlook.com ([fe80::6eb6:7d37:7b4b:1732%7]) with mapi id 15.20.8835.027; Wed, 18 Jun 2025 11:43:40 +0000 Date: Wed, 18 Jun 2025 08:43:39 -0300 From: Jason Gunthorpe To: Yi Liu Cc: Nicolin Chen , "Duan, Zhenzhong" , Peter Xu , "qemu-devel@nongnu.org" , "alex.williamson@redhat.com" , "clg@redhat.com" , "eric.auger@redhat.com" , "mst@redhat.com" , "jasowang@redhat.com" , "ddutile@redhat.com" , "shameerali.kolothum.thodi@huawei.com" , "joao.m.martins@oracle.com" , "clement.mathieu--drif@eviden.com" , "Tian, Kevin" , "Peng, Chao P" , Yi Sun , Marcel Apfelbaum , Paolo Bonzini , Richard Henderson , Eduardo Habkost Subject: Re: [PATCH rfcv3 15/21] intel_iommu: Bind/unbind guest page table to host Message-ID: <20250618114339.GF1575786@nvidia.com> References: <29f5f434-1fe3-4b5e-91d1-f153e1e98602@intel.com> <20250617123707.GW1174925@nvidia.com> <20250617131113.GX1174925@nvidia.com> <6a9f95b4-3e56-4ed3-b2a2-c41a6f728eb2@intel.com> Content-Type: text/plain; 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envelope-from=jgg@nvidia.com; helo=NAM02-SN1-obe.outbound.protection.outlook.com X-Spam_score_int: -39 X-Spam_score: -4.0 X-Spam_bar: ---- X-Spam_report: (-4.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.895, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Wed, Jun 18, 2025 at 11:40:38AM +0800, Yi Liu wrote: > Actually, as I explained in the first hunk of [1], there is no issue with > the legacy mode support. :) > > [1] https://lore.kernel.org/qemu-devel/20250521111452.3316354-1-zhenzhong.duan@intel.com/T/#m4c8fa70742001d4c22b3c297e240a2151d2c617f My feeling is that it is undesirable to have the shadowing code in the VMM at all, as it increases the attack surface/complexity/etc. There should be a way to fully inhibit legacy mode, and if that means old kernels don't work that's just how it is. Jason