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Peter Anvin" , Hugh Dickins , Jeff Layton , "J . Bruce Fields" , Andrew Morton , Mike Rapoport , "Maciej S . Szmigiero" , Vlastimil Babka , Vishal Annapurve , Yu Zhang , "Kirill A. Shutemov" , "Nakajima, Jun" , Dave Hansen , Andi Kleen , David Hildenbrand , Marc Zyngier , Will Deacon , nikunj@amd.com, ashish.kalra@amd.com References: <80aad2f9-9612-4e87-a27a-755d3fa97c92@www.fastmail.com> <83fd55f8-cd42-4588-9bf6-199cbce70f33@www.fastmail.com> <20220422105612.GB61987@chaop.bj.intel.com> <20220509223056.pyazfxjwjvipmytb@amd.com> From: "Gupta, Pankaj" In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: AS9P251CA0012.EURP251.PROD.OUTLOOK.COM (2603:10a6:20b:50f::14) To CY4PR1201MB0181.namprd12.prod.outlook.com (2603:10b6:910:1f::11) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 1c8b255a-0889-4432-cb74-08da6b545c21 X-MS-TrafficTypeDiagnostic: DM6PR12MB4107:EE_ X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: sEmKdjZAD9qshBW3nT+21kJBKQZsCqLDCjFqZQYFgyyfceVoecn4W30daLjcPmZt9iMwEDK6ZHm+Ws43qc8eaYJrQCBIYxhextSC1UP4QCX5Hwcwh6IPxgxL8L6okDH9Pi6F8bT3zUn5GoZrQU0JwbqQlwU+jNwRo2Zbryk/Bqys82Rw8AHENVzkoscwZrGqwwT5Sbp4FPLQV5AtproqpPalpw66N6FI1ybskVty5DrUtvRMz5mwePbrGMW4MyRK6pjRv71UK1ldE/6f7aRQq7u0uiZcKG0CNpXtngrJ0TbHXEyK0wt0+jq/QtPWc5bIC1/OdexNvVFuhTgUtITdt26J+EpCVJKrs0rD/qOO4oZIDkmRGl13RB32YqCUyFqwe++5RStrCQp6DYHLfT+boep2fYVBmdWXXjUV7NZqnfG6Js1/0HmLWKUWUmRZex5PCyhq5aYECutnndjYvl1cc7MmKAjyVtrFOlpsFYnXnoa/tddnsu7skl3CqBX7HsJa5jiCu6dtEEUNOkG5C2/MOg0HeGG1ZSN6jxkgXQoqeYABqUhmT6wNjLpyPM5WQi5a5LbtL2HNfg6/bFvMW16hadzrBD0dg+IE4JAnJUHowxomuOdmvdYStRPPa34qj7bToCflcPa+O0y9kRe9y4t5FaTj/sNxWtCqUKgdoCBGPL/mWEpAYX4zlsd729CRJ0IIOceyibsZtF+AVmEAZx2pqSGkfgjUb+A+fzBMrGlPs9N6OKelfEER5O73BEdMf2my3KSnUGVABEUiPr2o8radV099NlUAOYH6PccU4+RPROV8DjwVz7vAxlOavre0Cm+hXXA8qSRfjzc5Z60HSTIPcA== X-Forefront-Antispam-Report: CIP:255.255.255.255; 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envelope-from=Pankaj.Gupta@amd.com; helo=NAM10-DM6-obe.outbound.protection.outlook.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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" Hi Sean, Chao, While attempting to solve the pre-boot guest payload/firmware population into private memory for SEV SNP, retrieved this thread. Have question below: >>> Requirements & Gaps >>> ------------------------------------- >>> - Confidential computing(CC): TDX/SEV/CCA >>> * Need support both explicit/implicit conversions. >>> * Need support only destructive conversion at runtime. >>> * The current patch should just work, but prefer to have pre-boot guest >>> payload/firmware population into private memory for performance. >> >> Not just performance in the case of SEV, it's needed there because firmware >> only supports in-place encryption of guest memory, there's no mechanism to >> provide a separate buffer to load into guest memory at pre-boot time. I >> think you're aware of this but wanted to point that out just in case. > > I view it as a performance problem because nothing stops KVM from copying from > userspace into the private fd during the SEV ioctl(). What's missing is the > ability for userspace to directly initialze the private fd, which may or may not > avoid an extra memcpy() depending on how clever userspace is. Can you please elaborate more what you see as a performance problem? And possible ways to solve it? Thanks, Pankaj