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Peter Anvin" , Ard Biesheuvel , Paolo Bonzini , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Andy Lutomirski , Dave Hansen , Sergio Lopez , Peter Zijlstra , Srinivas Pandruvada , David Rientjes , Dov Murik , Tobin Feldman-Fitzthum , Michael Roth , Vlastimil Babka , "Kirill A . Shutemov" , Andi Kleen , tony.luck@intel.com, marcorr@google.com, sathyanarayanan.kuppuswamy@linux.intel.com Subject: Re: [PATCH Part2 v5 00/45] Add AMD Secure Nested Paging (SEV-SNP) Hypervisor Support To: Sean Christopherson References: <20210820155918.7518-1-brijesh.singh@amd.com> <061ccd49-3b9f-d603-bafd-61a067c3f6fa@intel.com> From: Brijesh Singh Message-ID: Date: Mon, 15 Nov 2021 12:58:54 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: MN2PR02CA0016.namprd02.prod.outlook.com (2603:10b6:208:fc::29) To SN6PR12MB2718.namprd12.prod.outlook.com (2603:10b6:805:6f::22) MIME-Version: 1.0 Received: from [10.236.30.107] (165.204.77.1) by MN2PR02CA0016.namprd02.prod.outlook.com (2603:10b6:208:fc::29) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4690.25 via Frontend Transport; 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If a kexec/kdump occurs while the VM is still active, the new >> kernel will encounter the #PF (RMP violation) because some pages are still >> marked 'private' in the RMP table. > > There are two basic options: a) eagerly purge the RMP or b) lazily fixup the RMP > on #PF. Either approach can be made to work. I'm not opposed to fixing up the RMP > on #PF in the kexec/kdump case, I'm opposed to blindly updating the RMP on _all_ > RMP #PFs, i.e. the kernel should modify the RMP if and only if it knows that doing > so is correct. E.g. a naive lazy-fixup solution would be to track which pages have > been sanitized and adjust the RMP on #PF to a page that hasn't yet been sanitized. > Yap, I think option #a will require the current kernel to iterate through the entire memory and make it shared before booting the kexec kernel. It may bring another ask to track the guest private/shared on the host to minimize the iterations. thanks