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Peter Anvin" , Ard Biesheuvel , Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Jim Mattson , Andy Lutomirski , Dave Hansen , Sergio Lopez , Peter Gonda , Peter Zijlstra , Srinivas Pandruvada , David Rientjes , Dov Murik , Tobin Feldman-Fitzthum , Borislav Petkov , Michael Roth , Vlastimil Babka , "Kirill A . Shutemov" , Andi Kleen , "Dr . David Alan Gilbert" , tony.luck@intel.com, marcorr@google.com, sathyanarayanan.kuppuswamy@linux.intel.com Subject: Re: [PATCH v8 09/40] x86/compressed: Add helper for validating pages in the decompression stage Content-Language: en-US To: Venu Busireddy References: <20211210154332.11526-1-brijesh.singh@amd.com> <20211210154332.11526-10-brijesh.singh@amd.com> From: Brijesh Singh In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-ClientProxiedBy: SN7PR04CA0100.namprd04.prod.outlook.com (2603:10b6:806:122::15) To SN6PR12MB2718.namprd12.prod.outlook.com (2603:10b6:805:6f::22) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: c9ee1d66-5f68-4a29-7edd-08d9c1b46a00 X-MS-TrafficTypeDiagnostic: SN1PR12MB2541:EE_ X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:8273; X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:SN6PR12MB2718.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(4636009)(366004)(6506007)(38100700002)(316002)(53546011)(54906003)(4326008)(66946007)(7406005)(44832011)(66556008)(7416002)(8676002)(66476007)(83380400001)(6486002)(2906002)(6512007)(186003)(5660300002)(31686004)(6916009)(86362001)(26005)(8936002)(31696002)(6666004)(36756003)(2616005)(508600001)(43740500002)(45980500001);DIR:OUT;SFP:1101; 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>> >> + /* >> + * If the encryption attribute is being cleared, then change >> + * the page state to shared in the RMP table. >> + */ >> + if (clr) > This function is also called by set_page_non_present() with clr set to > _PAGE_PRESENT. Do we want to change the page state to shared even when > the page is not present? If not, shouldn't the check be (clr & _PAGE_ENC)? I am not able to follow your comment. Here we only pay attention to the encryption attribute, if encryption attribute is getting cleared then make PSC. In the case ov set_page_non_present(), the outer if() block will return false.  Am I missing something ? >> + /* >> + * If private -> shared then invalidate the page before requesting the > This comment is confusing. We don't know what the present state is, > right? If we don't, shouldn't we just say: > > If the operation is SNP_PAGE_STATE_SHARED, invalidate the page before > requesting the state change in the RMP table. > By default all the pages are private, so I don't see any issue with saying "private -> shared". >> + * state change in the RMP table. >> + */ >> + if (op == SNP_PAGE_STATE_SHARED && pvalidate(paddr, RMP_PG_SIZE_4K, 0)) >> + sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_PVALIDATE); >> + >> + /* Issue VMGEXIT to change the page state in RMP table. */ >> + sev_es_wr_ghcb_msr(GHCB_MSR_PSC_REQ_GFN(paddr >> PAGE_SHIFT, op)); >> + VMGEXIT(); >> + >> + /* Read the response of the VMGEXIT. */ >> + val = sev_es_rd_ghcb_msr(); >> + if ((GHCB_RESP_CODE(val) != GHCB_MSR_PSC_RESP) || GHCB_MSR_PSC_RESP_VAL(val)) >> + sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_PSC); >> + >> + /* >> + * Now that page is added in the RMP table, validate it so that it is >> + * consistent with the RMP entry. > The page is not "added", right? Shouldn't we just say: Technically, PSC modifies the RMP entry, so I should use that  instead of calling "added". > Validate the page so that it is consistent with the RMP entry. Yes, I am okay with it. > Venu