[PATCH 4/6] Use MTRR for pci_mmap_resource_wc if PAT is not available

[Thomas Schlichter]

X.org uses libpciaccess which tries to mmap with write combining enabled via
/sys/bus/pci/devices/*/resource0_wc. Currently, when PAT is not enabled, we
fall back to uncached mmap. Then libpciaccess thinks it succeeded mapping
with write combining anabled and does not set up suited MTRR entries. ;-(

So when falling back to uncached mapping, we better try to set up MTRR
entries automatically. When the resource file is closed, we remove the MTRR
entries again.

Signed-off-by: Thomas Schlichter <thomas.schlichter@xxxxxx>
---
 drivers/pci/pci-sysfs.c |   45 +++++++++++++++++++++++++++++++++++++++++++--
 1 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 0f6382f..604a063 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -23,6 +23,11 @@
 #include <linux/mm.h>
 #include <linux/capability.h>
 #include <linux/pci-aspm.h>
+#include <linux/fs.h>
+#ifdef CONFIG_X86
+#  include <asm/mtrr.h>
+#  include <asm/pat.h>
+#endif
 #include "pci.h"
 
 static int sysfs_initialized;	/* = 0 */
@@ -692,9 +697,10 @@ pci_mmap_resource(struct kobject *kobj, struct bin_attribute *attr,
 	struct pci_dev *pdev = to_pci_dev(container_of(kobj,
 						       struct device, kobj));
 	struct resource *res = (struct resource *)attr->private;
+	struct bin_buffer *bb = (struct bin_buffer *)vma->vm_file->private_data;
 	enum pci_mmap_state mmap_type;
 	resource_size_t start, end;
-	int i;
+	int rc, i;
 
 	for (i = 0; i < PCI_ROM_RESOURCE; i++)
 		if (res == &pdev->resource[i])
@@ -716,7 +722,18 @@ pci_mmap_resource(struct kobject *kobj, struct bin_attribute *attr,
 	if (res->flags & IORESOURCE_MEM && iomem_is_exclusive(start))
 		return -EINVAL;
 
-	return pci_mmap_page_range(pdev, vma, mmap_type, write_combine);
+	rc = pci_mmap_page_range(pdev, vma, mmap_type, write_combine);
+#ifdef CONFIG_X86
+	if (!rc && !pat_enabled && write_combine) {
+		if (!bb->private)
+			bb->private = kzalloc(num_var_ranges * sizeof(int),
+					      GFP_KERNEL);
+		mtrr_add_unaligned(vma->vm_pgoff << PAGE_SHIFT,
+				   vma->vm_end - vma->vm_start,
+				   MTRR_TYPE_WRCOMB, true, bb->private);
+	}
+#endif // CONFIG_X86
+	return rc;
 }
 
 static int
@@ -733,6 +750,29 @@ pci_mmap_resource_wc(struct kobject *kobj, struct bin_attribute *attr,
 	return pci_mmap_resource(kobj, attr, vma, 1);
 }
 
+static int
+pci_release(struct kobject *kobj, struct bin_attribute *attr, struct file *file)
+{
+#ifdef CONFIG_X86
+	struct bin_buffer *bb = (struct bin_buffer *)file->private_data;
+	int i, *mtrr_usage = (int *)bb->private;
+
+	if (!mtrr_usage)
+		return 0;
+
+	for (i = 0; i < num_var_ranges; ++i) {
+		while (mtrr_usage[i] > 0) {
+			mtrr_del(i, 0, 0);
+			--mtrr_usage[i];
+		}
+	}
+
+	kfree(bb->private);
+	bb->private = NULL;
+#endif // CONFIG_X86
+	return 0;
+}
+
 /**
  * pci_remove_resource_files - cleanup resource files
  * @pdev: dev to cleanup
@@ -782,6 +822,7 @@ static int pci_create_attr(struct pci_dev *pdev, int num, int write_combine)
 			sprintf(res_attr_name, "resource%d", num);
 			res_attr->mmap = pci_mmap_resource_uc;
 		}
+		res_attr->release = pci_release;
 		res_attr->attr.name = res_attr_name;
 		res_attr->attr.mode = S_IRUSR | S_IWUSR;
 		res_attr->size = pci_resource_len(pdev, num);
-- 
1.6.5


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  charset="iso-8859-1";
  name="0006-Set-up-MTRR-entries-within-set_memory_wc.patch"
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Content-Disposition: inline;
	filename="0006-Set-up-MTRR-entries-within-set_memory_wc.patch"