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Thu, 15 Jan 2026 08:34:45 -0800 Date: Thu, 15 Jan 2026 08:34:43 -0800 From: Nicolin Chen To: Jason Gunthorpe CC: Will Deacon , , , , , , , , , Subject: Re: [PATCH rc v5 1/4] iommu/arm-smmu-v3: Add update_safe bits to fix STE update sequence Message-ID: References: <20260112161010.GC812923@nvidia.com> <20260113161253.GG812923@nvidia.com> <20260113205112.GJ812923@nvidia.com> <20260115131151.GA1081267@nvidia.com> <20260115162919.GG961588@nvidia.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20260115162919.GG961588@nvidia.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN2PEPF00004FBA:EE_|IA1PR12MB6556:EE_ X-MS-Office365-Filtering-Correlation-Id: 20e27909-df9a-4251-73b3-08de54540c72 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|82310400026|36860700013|1800799024; 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X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Jan 2026 16:35:09.4208 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 20e27909-df9a-4251-73b3-08de54540c72 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.161];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BN2PEPF00004FBA.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA1PR12MB6556 On Thu, Jan 15, 2026 at 12:29:19PM -0400, Jason Gunthorpe wrote: > On Thu, Jan 15, 2026 at 08:25:05AM -0800, Nicolin Chen wrote: > > On Thu, Jan 15, 2026 at 09:11:51AM -0400, Jason Gunthorpe wrote: > > > On Tue, Jan 13, 2026 at 04:51:12PM -0400, Jason Gunthorpe wrote: > > > > > - safe_bits[1] |= cpu_to_le64(STRTAB_STE_1_EATS); > > > > > + if (!((cur[2] | target[2]) & cpu_to_le64(STRTAB_STE_2_S2S))) > > > > > + safe_bits[1] |= cpu_to_le64( > > > > > + FIELD_PREP(STRTAB_STE_1_EATS, STRTAB_STE_1_EATS_TRANS)); > > > > > -------------------------------------------------------------------------- > > > > > > > > > > @will, does this look good to you? I can send a v7 with this. > > > > > > > > That is an easy way to address Will's observation, makes sense to me. > > > > > > Ah, but it looks like it can generate an errant view of a EATS that is > > > neither old or new. Ie value 3, reserved. > > > > > > I think you should just check if old or new has EATS bit 1 set: > > > > > > if (!((cur[2] | target[2]) & cpu_to_le64(STRTAB_STE_2_S2S)) && > > > !((cur[1] | target[1]) & cpu_to_le64(FIELD_PREP(STRTAB_STE_1_EATS, 2)))) > > > > > > Which the current driver never does.. > > > > The EATS field is completely controlled by the driver. So, we are > > safe for now, right? > > > > Should we add this when the driver has the actual support for the > > split stage thing? > > If we have figured it out now I would add it because it would be a big > leap to think the next person will remember about this detail.. > > But yes, this and the S2S thing don't effect the driver as it is now, > it is just doing work to help future people. OK. Let's add that. I will send the v7 by the end of the day. Hopefully, Will is okay with all of these.. Thanks Nicolin