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Fri, 17 Jun 2022 14:58:57 -0700 Date: Fri, 17 Jun 2022 14:58:56 -0700 From: Nicolin Chen To: Christoph Hellwig CC: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [RFT][PATCH v1 5/6] vfio/ccw: Add kmap_local_page() for memcpy Message-ID: References: <20220616235212.15185-1-nicolinc@nvidia.com> <20220616235212.15185-6-nicolinc@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 4e5aec02-7951-43ed-ef56-08da50ac95ba X-MS-TrafficTypeDiagnostic: BL1PR12MB5109:EE_ X-Microsoft-Antispam-PRVS: X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:12.22.5.234;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:InfoNoRecords;CAT:NONE;SFS:(13230016)(4636009)(46966006)(40470700004)(36840700001)(9686003)(54906003)(26005)(426003)(70206006)(82310400005)(86362001)(5660300002)(186003)(336012)(6916009)(47076005)(7416002)(4744005)(7406005)(55016003)(36860700001)(316002)(40460700003)(498600001)(356005)(83380400001)(33716001)(81166007)(2906002)(8936002)(4326008)(8676002)(70586007)(36900700001);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 17 Jun 2022 21:59:00.1905 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 4e5aec02-7951-43ed-ef56-08da50ac95ba X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[12.22.5.234];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: DM6NAM11FT056.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL1PR12MB5109 Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Fri, Jun 17, 2022 at 01:44:30AM -0700, Christoph Hellwig wrote: > On Thu, Jun 16, 2022 at 04:52:11PM -0700, Nicolin Chen wrote: > > The pinned PFN list returned from vfio_pin_pages() is simply converted > > using page_to_pfn() without protection, so direct access via memcpy() > > will crash on S390 if the PFN is an IO PFN. Instead, the pages should > > be touched using kmap_local_page(). > > I don't see how this helps. kmap_local_page only works for either > pages in the kernel direct map or highmem, but not for memory that needs > to be ioremapped. And there is no highmem on s390. Oh..I will discuss with Jason once he's back, to see if we should simply drop this change. Thanks!