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Message-ID: <8fb2f771-3354-3f52-f923-e7fe7861cfbf@suse.com> Date: Thu, 30 Mar 2023 08:24:20 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Subject: Re: [PATCH 4/5] multiboot2: parse console= option when setting GOP mode Content-Language: en-US To: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= Cc: marmarek@invisiblethingslab.com, Andrew Cooper , Wei Liu , xen-devel@lists.xenproject.org, Daniel Kiper References: <20221123154525.63068-1-roger.pau@citrix.com> <20221123154525.63068-5-roger.pau@citrix.com> <8f7e0393-8c0f-a924-7cee-25b9fca6f739@suse.com> From: Jan Beulich In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-ClientProxiedBy: FR0P281CA0073.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:1e::13) To VE1PR04MB6560.eurprd04.prod.outlook.com (2603:10a6:803:122::25) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: VE1PR04MB6560:EE_|AM7PR04MB7016:EE_ X-MS-Office365-Filtering-Correlation-Id: b435fd20-5700-404e-04bb-08db30e766c7 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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And how do you guarantee this? > > I think the comment is misleading, must be the last checked for tag in > the loop that does this in assembly, because it's not using cmove. > I've adjusted to: > > /* Get command line from Multiboot2 information. */ > cmpl $MULTIBOOT2_TAG_TYPE_CMDLINE,MB2_tag_type(%rcx) > jne .Lno_cmdline > lea MB2_tag_string(%rcx),%rdx > jmp .Lefi_mb2_next_tag > .Lno_cmdline: > > Maybe there's some instruction I'm missing similar to a conditional > lea? There isn't. If you want to get away without conditional branch, then you'll need to LEA to a scratch register (unconditional) and then CMOVcc from that scratch register. Jan