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Fri, 8 Jul 2022 22:44:49 +0000 Received: from drhqmail202.nvidia.com (10.126.190.181) by drhqmail201.nvidia.com (10.126.190.180) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.986.26; Fri, 8 Jul 2022 15:44:48 -0700 Received: from Asurada-Nvidia.nvidia.com (10.127.8.13) by mail.nvidia.com (10.126.190.181) with Microsoft SMTP Server id 15.2.986.26 via Frontend Transport; Fri, 8 Jul 2022 15:44:46 -0700 From: Nicolin Chen To: , , , , , , , , , , , , , , , , , , , , , , , , , , , CC: , , , , , , , , Subject: [PATCH v3 09/10] vfio/ccw: Add kmap_local_page() for memcpy Date: Fri, 8 Jul 2022 15:44:27 -0700 Message-ID: <20220708224427.1245-10-nicolinc@nvidia.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20220708224427.1245-1-nicolinc@nvidia.com> References: <20220708224427.1245-1-nicolinc@nvidia.com> MIME-Version: 1.0 X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: c0925e06-7428-4b4a-ea5f-08da61337721 X-MS-TrafficTypeDiagnostic: DS7PR12MB6359:EE_ X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Jul 2022 22:44:49.4565 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: c0925e06-7428-4b4a-ea5f-08da61337721 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[12.22.5.235];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BN8NAM11FT005.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS7PR12MB6359 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org A PFN is not secure enough to promise that the memory is not IO. And direct access via memcpy() that only handles CPU memory will crash on S390 if the PFN is an IO PFN, as we have to use the memcpy_to/fromio() that uses the special S390 IO access instructions. On the other hand, a "struct page *" is always a CPU coherent thing that fits memcpy(). Also, casting a PFN to "void *" for memcpy() is not a proper practice, kmap_local_page() is the correct API to call here, though S390 doesn't use highmem, which means kmap_local_page() is a NOP. There's a following patch changing the vfio_pin_pages() API to return a list of "struct page *" instead of PFNs. It will block any IO memory from ever getting into this call path, for such a security purpose. In this patch, add kmap_local_page() to prepare for that. Suggested-by: Jason Gunthorpe Reviewed-by: Jason Gunthorpe Acked-by: Eric Farman Tested-by: Eric Farman Signed-off-by: Nicolin Chen --- drivers/s390/cio/vfio_ccw_cp.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c index 3854c3d573f5..cd4ec4f6d6ff 100644 --- a/drivers/s390/cio/vfio_ccw_cp.c +++ b/drivers/s390/cio/vfio_ccw_cp.c @@ -11,6 +11,7 @@ #include #include #include +#include #include #include #include @@ -230,7 +231,6 @@ static long copy_from_iova(struct vfio_device *vdev, void *to, u64 iova, unsigned long n) { struct page_array pa = {0}; - u64 from; int i, ret; unsigned long l, m; @@ -246,7 +246,9 @@ static long copy_from_iova(struct vfio_device *vdev, void *to, u64 iova, l = n; for (i = 0; i < pa.pa_nr; i++) { - from = pa.pa_pfn[i] << PAGE_SHIFT; + struct page *page = pfn_to_page(pa.pa_pfn[i]); + void *from = kmap_local_page(page); + m = PAGE_SIZE; if (i == 0) { from += iova & (PAGE_SIZE - 1); @@ -254,7 +256,8 @@ static long copy_from_iova(struct vfio_device *vdev, void *to, u64 iova, } m = min(l, m); - memcpy(to + (n - l), (void *)from, m); + memcpy(to + (n - l), from, m); + kunmap_local(from); l -= m; if (l == 0)