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Message-ID: Date: Thu, 26 Oct 2023 14:35:53 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 Subject: Re: [PATCH] x86/hvm/dom0: fix PVH initrd and metadata placement Content-Language: en-US To: Xenia Ragiadakou Cc: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= , Wei Liu , xen-devel@lists.xenproject.org, Andrew Cooper References: <20231026064543.43369-1-xenia.ragiadakou@amd.com> <7712c60b-4f89-483e-89e4-7ac8f4d0311e@amd.com> <84b6679c-1956-4c6d-1fbd-b72846b69d1a@suse.com> From: Jan Beulich In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-ClientProxiedBy: FR5P281CA0003.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:f2::14) To DU2PR04MB8790.eurprd04.prod.outlook.com (2603:10a6:10:2e1::23) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DU2PR04MB8790:EE_|AS8PR04MB9205:EE_ X-MS-Office365-Filtering-Correlation-Id: ccdfc767-f08f-4850-8580-08dbd62018e9 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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I'd like to ask though >>>>> under what conditions that can happen, as it seems suspicious for the >>>>> kernel range to span multiple E820 ranges. >>>> We tried to boot Zephyr as pvh dom0 and its load address was under 1MB. >>>> >>>> I know ... that maybe shouldn't have been permitted at all, but >>>> nevertheless we hit this issue. >>> >>> Zephyr is linked to run at 4k. That's what the ELF Headers say, and the >>> entrypoint is not position-independent. >> Very interesting. What size is their kernel? And, Xenia, can you provide >> the E820 map that you were finding the collision with? > > Sure. > > Xen-e820 RAM map: > >  [0000000000000000, 000000000009fbff] (usable) >  [000000000009fc00, 000000000009ffff] (reserved) >  [00000000000f0000, 00000000000fffff] (reserved) >  [0000000000100000, 000000007ffdefff] (usable) >  [000000007ffdf000, 000000007fffffff] (reserved) >  [00000000b0000000, 00000000bfffffff] (reserved) >  [00000000fed1c000, 00000000fed1ffff] (reserved) >  [00000000fffc0000, 00000000ffffffff] (reserved) >  [0000000100000000, 000000027fffffff] (usable) > > (XEN) ELF: phdr: paddr=0x1000 memsz=0x8000 > (XEN) ELF: phdr: paddr=0x100000 memsz=0x28a90 > (XEN) ELF: phdr: paddr=0x128aa0 memsz=0x7560 > (XEN) ELF: memory: 0x1000 -> 0x130000 Oh, so it's not any particular range that crosses any E820 boundaries, but merely the total range including all holes which does. That raises the (only somewhat related) question what we would do with a kernel having a really large hole somewhere. Jan