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charset=UTF-8 Date: Fri, 26 Sep 2025 11:20:25 +0900 Message-Id: Subject: Re: [PATCH v2 05/10] gpu: nova-core: gsp: Add GSP command queue handling From: "Alexandre Courbot" To: "Alistair Popple" , "Lyude Paul" Cc: , , , , "Miguel Ojeda" , "Alex Gaynor" , "Boqun Feng" , "Gary Guo" , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , "Benno Lossin" , "Andreas Hindborg" , "Alice Ryhl" , "Trevor Gross" , "David Airlie" , "Simona Vetter" , "Maarten Lankhorst" , "Maxime Ripard" , "Thomas Zimmermann" , "John Hubbard" , "Joel Fernandes" , "Timur Tabi" , , X-Mailer: aerc 0.21.0-0-g5549850facc2 References: <20250922113026.3083103-1-apopple@nvidia.com> <20250922113026.3083103-6-apopple@nvidia.com> In-Reply-To: X-ClientProxiedBy: TYCP286CA0098.JPNP286.PROD.OUTLOOK.COM (2603:1096:400:2b4::19) To CH2PR12MB3990.namprd12.prod.outlook.com (2603:10b6:610:28::18) 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: CH2PR12MB3990:EE_|SJ1PR12MB6097:EE_ X-MS-Office365-Filtering-Correlation-Id: a04f66a5-254c-40fd-f601-08ddfca34275 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|7416014|376014|10070799003|1800799024; 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>> > + // TODO: find an alternative to as_flattened() >> > + #[allow(clippy::incompatible_msrv)] >> > + let (msg_header_slice, slice_1) =3D driver_area >> > + .0 >> > + .as_flattened() >> > + .split_at(size_of::()); >> > + >> > + // Can't fail because msg_slice will always be >> > + // size_of::() bytes long by the above spl= it. >> > + let msg_header =3D GspMsgElement::from_bytes(msg_header_s= lice).unwrap(); >>=20 >> Any reason we're not just using unwrap_unchecked() here then? > > Because whilst my assertions about the code are currently correct if it e= ver > changes I figured it would be better to explicitly panic than end up with > undefined behaviour. Is there some other advantage to using unwrap_unchec= ked()? > I can't imagine there'd be much of a performance difference. Here I think we should just use the `?` operator. The function already returns a `Result` so it would fit. I'd be willing to consider unwrapping is this can prevent an obviously-unfallible method from having to return a `Result` - but here this is not the case, and handling the error doesn't cost us more than the `unwrap`, so let's do that. >> > +impl GspRpcHeader { >> > + pub(crate) fn new(cmd_size: u32, function: u32) -> Self { >> > + Self { >> > + // TODO: magic number >> > + header_version: 0x03000000, >> > + signature: bindings::NV_VGPU_MSG_SIGNATURE_VALID, >> > + function, >> > + // TODO: overflow check? >> > + length: size_of::() as u32 + cmd_size, >>=20 >> (just curious, do you mean overflow as in arith overflow or overflow as = in >> going past the boundaries of the header?) > > Actually this snuck in from some of Alex's suggested code improvements (I= had > intended to credit him in the commit message! Will fix that) so maybe he = can > answer what he had in mind? I assumed arith overflow but maybe he meant r= ing > buffer overflow or something. I was thinking about arithmetic overflow, but maybe that was just overthinking. :) We're probably not going to send a 4 GB payload anytime soon...