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Wed, 16 Sep 2026 11:36:35 -0700 From: To: , , , , , , , , , , , , , , , , , , , , CC: , , , , , , , , , , , Subject: [PATCH v5 04/27] cxl: Add cxl_reset_dvsec_sequence() for vfio-pci Date: Thu, 17 Sep 2026 00:05:17 +0530 Message-ID: <20260916183540.3813685-5-mhonap@nvidia.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20260916183540.3813685-1-mhonap@nvidia.com> References: <20260916183540.3813685-1-mhonap@nvidia.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: rnnvmail202.nvidia.com (10.129.68.7) To rnnvmail202.nvidia.com (10.129.68.7) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LV8PEPF0000006B:EE_|CY8PR12MB7364:EE_ X-MS-Office365-Filtering-Correlation-Id: 4e96fd61-9e46-4ac6-3588-08df1421861e X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700016|82310400026|1800799024|23010399003|376014|7416014|22082099003|18002099003|921020|10067099003|56012099006|5023799004|11063799006|6133799003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: +t1sYfLkbPTBBEjJtGB5kdBd0uMuUl8krgn+I8OPJsFB73gsDQBum8bWT2bBusFQiV1dV2i0njBKTwkJ/4DQ3KAboOvdnkW/oAcEh9u+vbnB+BSGwvryDIM8jrllo3qH0eaC5p5/jOWdFvN7pgzv08e+tfggCfMGqRohbY/j4FKMDXokubKpQJzMVKiJZrM07TDn9TB+4Vph/1Vs4GsJY2p1Fg4GvzaflBxofxXYHU3lZ94QkFTArT0H/yNBjBtaINutv+SGC8EzOedOhDh3bhglLpRQSt0NmnSp/S40KbBd4zbjzT7+g501dmzJ6fIW1h/+1BBMfMB4lKkSgs9d9u/z1BBLyKSUOiSAyD13b6HhysDAzY1TEbJl9MvxLwbJm/Xe22HwikMInU2Z1F1GBtQsaCHokNOINtsBMv0Yyz3+dGWZRHxCcNFrKhwPvvVL X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 16 Sep 2026 18:37:12.4632 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 4e96fd61-9e46-4ac6-3588-08df1421861e X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.160];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: LV8PEPF0000006B.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY8PR12MB7364 From: Manish Honap vfio-pci needs to run a CXL reset on a passed-through Type-2 device without the host-memory handling in cxl_reset_function(): the memory behind the decoder belongs to the guest, so the HDM range collection and host CPU cache flush that the host path performs must be skipped. Add cxl_reset_dvsec_sequence(), which runs the DVSEC reset under the device lock and restores HDM state through cxl_restore_state_after_pci_reset(), and cxl_reset_capable() to gate it on a function-scoped reset. Both are exported to the vfio-cxl module so vfio-pci core does not import the CXL namespace. CXL Reset always clears memory, so there is no caller Memory Clear choice. Assisted-by: LLM Signed-off-by: Manish Honap --- drivers/cxl/core/resource.c | 53 +++++++++++++++++++++++++++++++++++++ include/cxl/cxl.h | 12 +++++++++ 2 files changed, 65 insertions(+) diff --git a/drivers/cxl/core/resource.c b/drivers/cxl/core/resource.c index d3491e20c1ca..d373df9aa127 100644 --- a/drivers/cxl/core/resource.c +++ b/drivers/cxl/core/resource.c @@ -1398,3 +1398,56 @@ int cxl_reset_function(struct pci_dev *pdev, bool probe) cxl_pci_target_reset_done(pdev, &target_prepared); return rc; } + +/* True when a function-scoped CXL reset is available for @pdev. */ +bool cxl_reset_capable(struct pci_dev *pdev) +{ + u16 cap; + + if (cxl_reset_get_dvsec(pdev, &cap) < 0) + return false; + + if (pdev->multifunction || pci_num_vf(pdev)) + return false; + + return cxl_reset_hdm_available(pdev); +} +EXPORT_SYMBOL_FOR_MODULES(cxl_reset_capable, "vfio-cxl"); + +/* + * Run the DVSEC reset sequence and restore HDM state for a caller that owns + * device quiesce and PCI config save/restore, such as vfio-pci. + * The HDM range collection and host CPU cache flush that cxl_reset_function() + * performs for host-owned memory are skipped as that memory belongs to the + * guest. + */ +int cxl_reset_dvsec_sequence(struct pci_dev *pdev) +{ + bool target_prepared = false; + bool reset_initiated = false; + int dvsec; + int rc; + u16 cap; + + dvsec = cxl_reset_get_dvsec(pdev, &cap); + if (dvsec < 0) + return dvsec; + + if (pdev->multifunction || pci_num_vf(pdev)) + return -ENOTTY; + + if (!pci_dev_trylock(pdev)) + return -EBUSY; + + rc = cxl_reset_execute(pdev, &target_prepared, &reset_initiated, dvsec, + cap); + if (!rc) + rc = cxl_restore_state_after_pci_reset(pdev); + else if (reset_initiated) + cxl_reset_save_disabled_state(pdev); + + cxl_pci_target_reset_done(pdev, &target_prepared); + pci_dev_unlock(pdev); + return rc; +} +EXPORT_SYMBOL_FOR_MODULES(cxl_reset_dvsec_sequence, "vfio-cxl"); diff --git a/include/cxl/cxl.h b/include/cxl/cxl.h index 92314f67b702..a28903fc2960 100644 --- a/include/cxl/cxl.h +++ b/include/cxl/cxl.h @@ -168,6 +168,8 @@ void pci_cxl_hdm_init(struct pci_dev *pdev); void pci_cxl_hdm_release(struct pci_dev *pdev); int cxl_restore_state_after_pci_reset(struct pci_dev *pdev); int cxl_reset_function(struct pci_dev *pdev, bool probe); +bool cxl_reset_capable(struct pci_dev *pdev); +int cxl_reset_dvsec_sequence(struct pci_dev *pdev); #else static inline void pci_cxl_hdm_init(struct pci_dev *pdev) { @@ -186,6 +188,16 @@ static inline int cxl_reset_function(struct pci_dev *pdev, bool probe) { return -ENOTTY; } + +static inline bool cxl_reset_capable(struct pci_dev *pdev) +{ + return false; +} + +static inline int cxl_reset_dvsec_sequence(struct pci_dev *pdev) +{ + return -ENOTTY; +} #endif struct cxl_reg_map { -- 2.25.1