From patchwork Mon Mar 11 20:39:53 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dave Jiang X-Patchwork-Id: 13589310 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 051EC56B6F; Mon, 11 Mar 2024 20:41:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710189708; cv=none; b=kW89QuVqEEageQZ3AvAu2qxCzSV7Kh5jywgaXTZkBnJTTRkyAUafbJ2eewJVQhaXP+ebDCLNYVEFAiIAFjCMaZquLc2TOSA2ZFoCxydr/xKIqcExLhFwcGI9gNorVk7ATXaY8iOS5koZDk39WhhCf2pQ0zIYeS33/rDR0ED3vy8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710189708; c=relaxed/simple; bh=2M4ITpyEL+gdUTWCafXQu5fJYPdFIH6LMSuR0+oAl+0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=SzTFGiB8ljoaRHnLSe1GUCGkAjz28z9+Fai9nXXRJiw0loAlIkvLlaa5StXYgGspaSSlEcPxVIXvxy9K9SheA4HU3fHC2e2vDLVAIT00cv5WwvXobJquZX7ZS6mQXOtIia0TK2tIZJcgLVfEwtQc5OYrdyGn8qlKqrFOfegQ4PM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id B0DC5C433C7; Mon, 11 Mar 2024 20:41:46 +0000 (UTC) From: Dave Jiang To: linux-cxl@vger.kernel.org, linux-pci@vger.kernel.org Cc: dan.j.williams@intel.com, ira.weiny@intel.com, vishal.l.verma@intel.com, alison.schofield@intel.com, Jonathan.Cameron@huawei.com, dave@stgolabs.net, bhelgaas@google.com, lukas@wunner.de Subject: [PATCH 1/3] PCI: Add check for CXL Secondary Bus Reset Date: Mon, 11 Mar 2024 13:39:53 -0700 Message-ID: <20240311204132.62757-2-dave.jiang@intel.com> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240311204132.62757-1-dave.jiang@intel.com> References: <20240311204132.62757-1-dave.jiang@intel.com> Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Per CXL spec r3.1 8.1.5.2, secondary bus reset is masked unless the "Unmask SBR" bit is set. Add a check to the PCI secondary bus reset path to fail the CXL SBR request if the "Unmask SBR" bit is clear in the CXL Port Control Extensions regiser by returning -EPERM. The expectation is that if a user overrides the "Unmask SBR" via a user tool such as setpci, they can trigger a bus reset after that. Signed-off-by: Dave Jiang --- drivers/cxl/cxlpci.h | 2 -- drivers/pci/pci.c | 45 +++++++++++++++++++++++++++++++++++ include/uapi/linux/pci_regs.h | 7 ++++++ 3 files changed, 52 insertions(+), 2 deletions(-) diff --git a/drivers/cxl/cxlpci.h b/drivers/cxl/cxlpci.h index 711b05d9a370..8d7952d7ca59 100644 --- a/drivers/cxl/cxlpci.h +++ b/drivers/cxl/cxlpci.h @@ -13,10 +13,8 @@ * "DVSEC" redundancies removed. When obvious, abbreviations may be used. */ #define PCI_DVSEC_HEADER1_LENGTH_MASK GENMASK(31, 20) -#define PCI_DVSEC_VENDOR_ID_CXL 0x1E98 /* CXL 2.0 8.1.3: PCIe DVSEC for CXL Device */ -#define CXL_DVSEC_PCIE_DEVICE 0 #define CXL_DVSEC_CAP_OFFSET 0xA #define CXL_DVSEC_MEM_CAPABLE BIT(2) #define CXL_DVSEC_HDM_COUNT_MASK GENMASK(5, 4) diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index c3585229c12a..5e5550f54053 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -5347,10 +5347,55 @@ static int pci_dev_reset_slot_function(struct pci_dev *dev, bool probe) return pci_reset_hotplug_slot(dev->slot->hotplug, probe); } +static bool is_cxl_device(struct pci_dev *dev) +{ + return pci_find_dvsec_capability(dev, PCI_DVSEC_VENDOR_ID_CXL, + CXL_DVSEC_PCIE_DEVICE); +} + +static bool is_cxl_port_sbr_masked(struct pci_dev *dev) +{ + int dvsec; + int rc; + u16 reg; + + /* + * No DVSEC found, must not be CXL port. + */ + dvsec = pci_find_dvsec_capability(dev, PCI_DVSEC_VENDOR_ID_CXL, + CXL_DVSEC_PCIE_PORT); + if (!dvsec) + return false; + + rc = pci_read_config_word(dev, dvsec + CXL_DVSEC_PORT_CONTROL, ®); + if (rc) + return true; + + /* + * CXL spec r3.1 8.1.5.2 + * When 0, SBR bit in Bridge Control register of this Port has no effect. + * When 1, the Port shall generate hot reset when SBR bit in Bridge + * Control gets set to 1. + */ + if (reg & CXL_DVSEC_PORT_CONTROL_UNMASK_SBR) + return false; + + return true; +} + static int pci_reset_bus_function(struct pci_dev *dev, bool probe) { int rc; + /* If it's a CXL port and the SBR control is masked, fail the SBR */ + if (is_cxl_device(dev) && dev->bus->self && + is_cxl_port_sbr_masked(dev->bus->self)) { + if (probe) + return 0; + + return -EPERM; + } + rc = pci_dev_reset_slot_function(dev, probe); if (rc != -ENOTTY) return rc; diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h index a39193213ff2..5f2c66987299 100644 --- a/include/uapi/linux/pci_regs.h +++ b/include/uapi/linux/pci_regs.h @@ -1148,4 +1148,11 @@ #define PCI_DOE_DATA_OBJECT_DISC_RSP_3_PROTOCOL 0x00ff0000 #define PCI_DOE_DATA_OBJECT_DISC_RSP_3_NEXT_INDEX 0xff000000 +/* Compute Express Link (CXL) */ +#define PCI_DVSEC_VENDOR_ID_CXL 0x1e98 +#define CXL_DVSEC_PCIE_DEVICE 0 +#define CXL_DVSEC_PCIE_PORT 3 +#define CXL_DVSEC_PORT_CONTROL 0x0c +#define CXL_DVSEC_PORT_CONTROL_UNMASK_SBR 0x00000001 + #endif /* LINUX_PCI_REGS_H */