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b=bmVG/CKQj3MEhqJLei/8f/aYOWy9R095Td/W0vMhHsEMEkiPyFIwZnrXRgwAXMetIYLzlamnpSWfrw/sG77I3BQUXxXw6rbhLYYLXE8meV2TenBFj2JVLflHFlYDsk7ZLm09aq/X3G1zHteorqwl6RdT6l/CveI1/2dQ5gfyyAE= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=amd.com; Received: from BL3PR12MB9049.namprd12.prod.outlook.com (2603:10b6:208:3b8::21) by BL1PR12MB5729.namprd12.prod.outlook.com (2603:10b6:208:384::14) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.7875.21; Thu, 29 Aug 2024 14:30:58 +0000 Received: from BL3PR12MB9049.namprd12.prod.outlook.com ([fe80::c170:6906:9ef3:ecef]) by BL3PR12MB9049.namprd12.prod.outlook.com ([fe80::c170:6906:9ef3:ecef%6]) with mapi id 15.20.7897.021; Thu, 29 Aug 2024 14:30:57 +0000 Message-ID: <3f887fb7-e30e-41f4-8ac1-bd245e707ccc@amd.com> Date: Thu, 29 Aug 2024 09:30:54 -0500 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] x86/sev: Fix host kdump support for SNP Content-Language: en-US To: Borislav Petkov , seanjc@google.com, pbonzini@redhat.com, dave.hansen@linux.intel.com, tglx@linutronix.de, mingo@redhat.com, x86@kernel.org Cc: hpa@zytor.com, peterz@infradead.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, thomas.lendacky@amd.com, michael.roth@amd.com, kexec@lists.infradead.org, linux-coco@lists.linux.dev References: <20240827203804.4989-1-Ashish.Kalra@amd.com> <87475131-856C-44DC-A27A-84648294F094@alien8.de> From: "Kalra, Ashish" In-Reply-To: <87475131-856C-44DC-A27A-84648294F094@alien8.de> Content-Type: text/plain; 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If SNP_SHUTDOWN is not done, then crashkernel panics during boot as the crashdump attached to the fix/patch here shows, so essentially if SNP_DECOMMISSION followed by SNP_SHUTDOWN is not done then we can't boot crashkernel in case of any active SNP guests (which i will believe is an important requirement for cloud providers). Additionally, in case of SNP_DECOMMISSION, the firmware marks the ASID of the guest as not runnable and then transitions the SNP guest context page into a Firmware page (so that is one RMP table change) and for SNP_SHUTDOWN_EX, the firmware transitions all pages associated with the IOMMU to the Reclaim state (which then the HV marks as hypervisor pages), these IOMMU pages are the event log, PPR log, and completion wait buffers of the IOMMU. Aside from the IOMMU pages mentioned above, the firmware will not automatically reclaim or modify any other pages in the RMP table and also does not reset the RMP table. So essentially all host memory (and guest data) will still be available and saved by crashkernel. Thanks, Ashish