linux-kernel - [PATCH V3 2/2] cxl/doe: Request exclusive DOE access

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Message-Id: <20220926215711.2893286-3-ira.weiny@intel.com>
Date:   Mon, 26 Sep 2022 14:57:11 -0700
From:   ira.weiny@...el.com
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     Ira Weiny <ira.weiny@...el.com>,
        Alison Schofield <alison.schofield@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Ben Widawsky <bwidawsk@...nel.org>, linux-cxl@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: [PATCH V3 2/2] cxl/doe: Request exclusive DOE access

From: Ira Weiny <ira.weiny@...el.com>

The PCIE Data Object Exchange (DOE) mailbox is a protocol run over
configuration cycles.  It assumes one initiator at a time.  While the
kernel has control of the mailbox user space writes could interfere with
the kernel access.

Mark DOE mailbox config space exclusive when iterated by the CXL driver.

Signed-off-by: Ira Weiny <ira.weiny@...el.com>

---
Changes from V2:
	Jonathan:
		s/PCI_DOE_CAP_SIZE/PCI_DOE_CAP_SIZEOF
		Set PCI_DOE_CAP_SIZEOF directly
---
 drivers/cxl/pci.c             | 5 +++++
 include/uapi/linux/pci_regs.h | 1 +
 2 files changed, 6 insertions(+)

diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
index faeb5d9d7a7a..621a0522b554 100644
--- a/drivers/cxl/pci.c
+++ b/drivers/cxl/pci.c
@@ -418,6 +418,11 @@ static void devm_cxl_pci_create_doe(struct cxl_dev_state *cxlds)
 			continue;
 		}
 
+		if (!pci_request_config_region_exclusive(pdev, off,
+							 PCI_DOE_CAP_SIZEOF,
+							 dev_name(dev)))
+			pci_err(pdev, "Failed to exclude DOE registers\n");
+
 		if (xa_insert(&cxlds->doe_mbs, off, doe_mb, GFP_KERNEL)) {
 			dev_err(dev, "xa_insert failed to insert MB @ %x\n",
 				off);
diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
index 57b8e2ffb1dd..82a03ea954af 100644
--- a/include/uapi/linux/pci_regs.h
+++ b/include/uapi/linux/pci_regs.h
@@ -1119,6 +1119,7 @@
 #define  PCI_DOE_STATUS_DATA_OBJECT_READY	0x80000000  /* Data Object Ready */
 #define PCI_DOE_WRITE		0x10    /* DOE Write Data Mailbox Register */
 #define PCI_DOE_READ		0x14    /* DOE Read Data Mailbox Register */
+#define PCI_DOE_CAP_SIZEOF	0x18	/* Size of DOE register block */
 
 /* DOE Data Object - note not actually registers */
 #define PCI_DOE_DATA_OBJECT_HEADER_1_VID		0x0000ffff
-- 
2.37.2