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Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH] accel/amdxdna: document trusted mailbox ring geometry and drop the power-of-two check Content-Language: en-US To: Eva Crystal <0xiviel@gmail.com>, Min Ma , Oded Gabbay CC: Max Zhen , , , , References: <67698952-6394-44a8-01fe-3e3558b7cb4c@amd.com> <20261002205814.178031-1-0xiviel@gmail.com> From: Lizhi Hou In-Reply-To: <20261002205814.178031-1-0xiviel@gmail.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BY1PEPF0001AE1B:EE_|MW4PR12MB5666:EE_ X-MS-Office365-Filtering-Correlation-Id: 75e6cf85-8e6d-40f3-8051-08df23c274d1 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700016|1800799024|82310400026|376014|23010399003|22082099003|18002099003|10067099003|13003099007|4143699003|5023799004|11063799006|56012099006; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:satlexmb08.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(36860700016)(1800799024)(82310400026)(376014)(23010399003)(22082099003)(18002099003)(10067099003)(13003099007)(4143699003)(5023799004)(11063799006)(56012099006);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: 48CElgeCcNkyLfdWDY5A7b+Ywl/mxZc6Es5GDf9ZCV864tLqmzODc3WhRHSCsMAsFztQTishyDT8bytRtKrPWQeuM8t5Y2qar7TisPxOQldg36BNsYADoFIEYrSYmqicZJHuYRNu4Zpg7AuTdcd65j7d80YdvZGH2rXHv5Ie6whBnOBfx5VAHvELOuvk54YwgpjXcFnz9r8pF1QW9t6syOCHMI0NTbnopsCWiM6bTpSmHp67KjrtD2wqGXinGfVIELdmtpbjmBprVT+9j6XB1HAH/pWeFLVjhMrwmIrFxTeZMcmtILTIBPluBr3h+mXTqsM/N1jk5swPboiZwBvmfGcM0b9p+exa+bSYVBvdNNg+fyavszzV1sE9QBx3xuIXi6pjmqIRUXaZnWZM9RmH6HXgihelIDmsrQgwSUEV8c1ZzABXNxiWo0Cog3cox2qg X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Oct 2026 15:56:59.9142 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 75e6cf85-8e6d-40f3-8051-08df23c274d1 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb08.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BY1PEPF0001AE1B.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW4PR12MB5666 On 10/2/26 13:58, Eva Crystal wrote: > The mailbox ring buffer geometry comes from AMD signed firmware, through > the management or mailbox information block, or through the CREATE_CONTEXT > response, and the driver trusts it by design. > > The power-of-two test on rb_size was a firmware debugging aid. Nothing in > the driver derives a mask, a shift or a modulo from rb_size, so no code > depends on the property it tested. The ring index wrap is handled by the > explicit comparisons in mailbox_send_msg() and mailbox_get_msg(). > > Replace the test with a comment that records the design, so that > automated review does not flag the absence of a bound here again. > > Suggested-by: Lizhi Hou > Link: https://lore.kernel.org/all/67698952-6394-44a8-01fe-3e3558b7cb4c@amd.com/ > Signed-off-by: Eva Crystal <0xiviel@gmail.com> > --- > The pkg_size check in xdna_mailbox_send_msg() is left in place on > purpose: it bounds a driver-supplied size, and with Max Zhen's pool > patch (20261002161122.1350075-1-max.zhen@amd.com) it is the only bound > on the write into a pre-allocated message slot. > > drivers/accel/amdxdna/amdxdna_mailbox.c | 12 +++++++----- > 1 file changed, 7 insertions(+), 5 deletions(-) > > diff --git a/drivers/accel/amdxdna/amdxdna_mailbox.c b/drivers/accel/amdxdna/amdxdna_mailbox.c > index 05c3786de135..c4a36858668f 100644 > --- a/drivers/accel/amdxdna/amdxdna_mailbox.c > +++ b/drivers/accel/amdxdna/amdxdna_mailbox.c > @@ -513,11 +513,13 @@ xdna_mailbox_start_channel(struct mailbox_channel *mb_chann, > { > int ret; > > - if (!is_power_of_2(x2i->rb_size) || !is_power_of_2(i2x->rb_size)) { > - pr_err("Ring buf size must be power of 2\n"); > - return -EINVAL; > - } > - > + /* > + * The ring buffer geometry, rb_start_addr and rb_size for both the > + * x2i and the i2x channel, comes from AMD signed firmware, through > + * the management or mailbox information block, or through the > + * CREATE_CONTEXT response. The driver trusts those values by design > + * and does not bound them against the mapped region. > + */ Reviewed-by: Lizhi Hou > mb_chann->msix_irq = mb_irq; > mb_chann->iohub_int_addr = iohub_int_addr; > memcpy(&mb_chann->res[CHAN_RES_X2I], x2i, sizeof(*x2i));