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[142.68.128.5]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6e65d9f325fsm68981726d6.76.2025.02.18.15.51.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 18 Feb 2025 15:51:06 -0800 (PST) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1tkXMn-0000000020v-3I9I; Tue, 18 Feb 2025 19:51:05 -0400 Date: Tue, 18 Feb 2025 19:51:05 -0400 From: Jason Gunthorpe To: Alexey Kardashevskiy Cc: x86@kernel.org, kvm@vger.kernel.org, linux-crypto@vger.kernel.org, linux-pci@vger.kernel.org, linux-arch@vger.kernel.org, Sean Christopherson , Paolo Bonzini , Tom Lendacky , Ashish Kalra , Joerg Roedel , Suravee Suthikulpanit , Robin Murphy , Kevin Tian , Bjorn Helgaas , Dan Williams , Christoph Hellwig , Nikunj A Dadhania , Michael Roth , Vasant Hegde , Joao Martins , Nicolin Chen , Lu Baolu , Steve Sistare , Lukas Wunner , Jonathan Cameron , Suzuki K Poulose , Dionna Glaze , Yi Liu , iommu@lists.linux.dev, linux-coco@lists.linux.dev, Zhi Wang , AXu Yilun , "Aneesh Kumar K . V" Subject: Re: [RFC PATCH v2 12/22] iommufd: Allow mapping from guest_memfd Message-ID: <20250218235105.GK3696814@ziepe.ca> References: <20250218111017.491719-1-aik@amd.com> <20250218111017.491719-13-aik@amd.com> <20250218141634.GI3696814@ziepe.ca> <340d8dba-1b09-4875-8604-cd9f66ca1407@amd.com> 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: <340d8dba-1b09-4875-8604-cd9f66ca1407@amd.com> On Wed, Feb 19, 2025 at 10:35:28AM +1100, Alexey Kardashevskiy wrote: > With in-place conversion, we could map the entire guest once in the HV IOMMU > and control the Cbit via the guest's IOMMU table (when available). Thanks, Isn't it more complicated than that? I understood you need to have a IOPTE boundary in the hypervisor at any point where the guest Cbit changes - so you can't just dump 1G hypervisor pages to cover the whole VM, you have to actively resize ioptes? This was the whole motivation to adding the page size override kernel command line. Jason