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charset=UTF-8 Date: Wed, 15 Apr 2026 11:35:18 +0900 Message-Id: From: "Eliot Courtney" To: "Timur Tabi" , "Alexandre Courbot" , "dakr@kernel.org" , "Eliot Courtney" , "Joel Fernandes" , "John Hubbard" , "rust-for-linux@vger.kernel.org" Subject: Re: [PATCH 3/6] gpu: nova-core: only boot FRTS if it actually exists X-Mailer: aerc 0.21.0-0-g5549850facc2 References: <20260410203722.1586938-1-ttabi@nvidia.com> <20260410203722.1586938-4-ttabi@nvidia.com> <15e06581b295691731145b55ecc337ea2ed8dcba.camel@nvidia.com> <838f5d39768881b05fa83c20f2706faf2b043a43.camel@nvidia.com> In-Reply-To: <838f5d39768881b05fa83c20f2706faf2b043a43.camel@nvidia.com> X-ClientProxiedBy: TYCPR01CA0099.jpnprd01.prod.outlook.com (2603:1096:405:4::15) To BL0PR12MB2353.namprd12.prod.outlook.com (2603:10b6:207:4c::31) Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BL0PR12MB2353:EE_|DS2PR12MB9709:EE_ X-MS-Office365-Filtering-Correlation-Id: c68a7687-1491-445f-ae19-08de9a97a494 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|10070799003|366016|22082099003|56012099003|18002099003; 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I think it will make it clearer in other locations that use >> > > FRTS that it possibly might not exist. >> >=20 >> > Yeah, I like that. >>=20 >> Actually, using Option won't work.=C2=A0 The problem is that ev= en if frtsSize is 0, frtsStart >> (aka frtsOffset) must still be a non-zero number, which means we still n= eed to keep the FbRange, >> but >> it would need to be FbRange. >>=20 >> So I can update the HAL, but not the FbRange code. > > So after working on this a bit, I don't think it's actually going to impr= ove things. The problem is > that even though I saw that "the FRTS region doesn't exist", it kinda doe= s, it's just zero size.=20 > That's because GSP-RM actually cares (and uses) frtsStart (RM calls it fr= tsOffset) even if frtsSize > is zero. So we need to keep the FbRange no matter what. Changing frts_s= ize() to return an > Option results in this code: > > let frts_size =3D hal.frts_size().map_or(0, |n| n.get()); > > We all know what's actually going on internally, but this line just obfus= cates it. > > I will reword the commit messages to say that the window is zero size rat= her than being non- > existent. That seems fair enough, thank you for trying it out.