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Peter Anvin" , Ard Biesheuvel , Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Andy Lutomirski , Dave Hansen , Sergio Lopez , Peter Gonda , Peter Zijlstra , Srinivas Pandruvada , David Rientjes , Dov Murik , Tobin Feldman-Fitzthum , Michael Roth , Vlastimil Babka , tony.luck@intel.com, npmccallum@redhat.com, brijesh.ksingh@gmail.com Subject: Re: [PATCH Part1 RFC v4 15/36] x86/mm: Add support to validate memory when changing C-bit To: Borislav Petkov References: <20210707181506.30489-1-brijesh.singh@amd.com> <20210707181506.30489-16-brijesh.singh@amd.com> From: Brijesh Singh Message-ID: Date: Tue, 17 Aug 2021 15:34:41 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: SA9P223CA0030.NAMP223.PROD.OUTLOOK.COM (2603:10b6:806:26::35) To SN6PR12MB2718.namprd12.prod.outlook.com (2603:10b6:805:6f::22) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [10.236.31.95] (165.204.77.1) by SA9P223CA0030.NAMP223.PROD.OUTLOOK.COM (2603:10b6:806:26::35) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4436.19 via Frontend Transport; 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dkim=pass header.d=amd.com header.s=selector1 header.b=0Fyl9REp; dmarc=pass (policy=quarantine) header.from=amd.com; spf=pass (imf20.hostedemail.com: domain of brijesh.singh@amd.com designates 40.107.93.46 as permitted sender) smtp.mailfrom=brijesh.singh@amd.com X-Stat-Signature: wihdi7q8bfptzu1dtbuqfi1jom3ushks X-Rspamd-Queue-Id: A0FBDD000659 X-Rspamd-Server: rspam05 X-HE-Tag: 1629232487-268550 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi Boris, On 8/17/21 12:27 PM, Borislav Petkov wrote: > >> + /* Lets verify that reserved bit is not set in the header*/ >> + if (WARN(hdr->reserved, "Reserved bit is set in the PSC header\n")) > > psc_entry has a ->reserved field too and since we're iterating over the > entries... > I am not seeing any strong reason to sanity check the reserved bit in the psc_entry. The fields in the psc_entry are input from guest to the hypervisor. The hypervisor cannot trick a guest by changing anything in the psc_entry because guest does not read the hypervisor filled value. I am okay with the psc_hdr because we need to read the current and end entry after the PSC completes to determine whether it was successful and sanity checking PSC header makes much more sense. Let me know if you are okay with it ? thanks