[PATCH 04/17] pci: Add arch_can_pci_mmap_wc() macro
From: David Woodhouse
Date: Wed Mar 22 2017 - 09:31:58 EST
From: David Woodhouse <dwmw@xxxxxxxxxxxx>
Most of the almost-identical versions of pci_mmap_page_range() silently
ignore the 'write_combine' argument and give uncached mappings.
Yet we allow the PCIIOC_WRITE_COMBINE ioctl in /proc/bus/pci, expose the
'resourceX_wc' file in sysfs, and allow an attempted mapping to apparently
succeed.
To fix this, introduce a macro arch_can_pci_mmap_wc() which indicates
whether the platform can do a write-combining mapping. On x86 this ends
up being pat_enabled(), while the few other platforms that support it
can just set it to a literal '1'.
Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
---
Documentation/filesystems/sysfs-pci.txt | 4 ++++
arch/ia64/include/asm/pci.h | 2 ++
arch/powerpc/include/asm/pci.h | 5 +++--
arch/x86/include/asm/pci.h | 2 ++
arch/xtensa/include/asm/pci.h | 6 +++++-
arch/xtensa/kernel/pci.c | 2 +-
drivers/pci/pci-sysfs.c | 6 ++++--
drivers/pci/proc.c | 17 ++++++++++-------
8 files changed, 31 insertions(+), 13 deletions(-)
diff --git a/Documentation/filesystems/sysfs-pci.txt b/Documentation/filesystems/sysfs-pci.txt
index 6ea1ced..25b7f1c 100644
--- a/Documentation/filesystems/sysfs-pci.txt
+++ b/Documentation/filesystems/sysfs-pci.txt
@@ -117,6 +117,10 @@ code must define HAVE_PCI_MMAP and provide a pci_mmap_page_range function.
Platforms are free to only support subsets of the mmap functionality, but
useful return codes should be provided.
+Platforms which support write-combining maps of PCI resources must define
+arch_can_pci_mmap_wc() which shall evaluate to non-zero at runtime when
+write-combining is permitted.
+
Legacy resources are protected by the HAVE_PCI_LEGACY define. Platforms
wishing to support legacy functionality should define it and provide
pci_legacy_read, pci_legacy_write and pci_mmap_legacy_page_range functions.
diff --git a/arch/ia64/include/asm/pci.h b/arch/ia64/include/asm/pci.h
index c0835b0..6283758 100644
--- a/arch/ia64/include/asm/pci.h
+++ b/arch/ia64/include/asm/pci.h
@@ -51,6 +51,8 @@ extern unsigned long ia64_max_iommu_merge_mask;
#define PCI_DMA_BUS_IS_PHYS (ia64_max_iommu_merge_mask == ~0UL)
#define HAVE_PCI_MMAP
+#define arch_can_pci_mmap_wc() 1
+
extern int pci_mmap_page_range (struct pci_dev *dev, struct vm_area_struct *vma,
enum pci_mmap_state mmap_state, int write_combine);
#define HAVE_PCI_LEGACY
diff --git a/arch/powerpc/include/asm/pci.h b/arch/powerpc/include/asm/pci.h
index 93eded8..b5b68c6 100644
--- a/arch/powerpc/include/asm/pci.h
+++ b/arch/powerpc/include/asm/pci.h
@@ -81,8 +81,9 @@ struct vm_area_struct;
int pci_mmap_page_range(struct pci_dev *pdev, struct vm_area_struct *vma,
enum pci_mmap_state mmap_state, int write_combine);
-/* Tell drivers/pci/proc.c that we have pci_mmap_page_range() */
-#define HAVE_PCI_MMAP 1
+/* Tell drivers/pci/proc.c that we have pci_mmap_page_range() and it does WC */
+#define HAVE_PCI_MMAP 1
+#define arch_can_pci_mmap_wc() 1
extern int pci_legacy_read(struct pci_bus *bus, loff_t port, u32 *val,
size_t count);
diff --git a/arch/x86/include/asm/pci.h b/arch/x86/include/asm/pci.h
index 1411dbe..f6e22c2 100644
--- a/arch/x86/include/asm/pci.h
+++ b/arch/x86/include/asm/pci.h
@@ -7,6 +7,7 @@
#include <linux/string.h>
#include <linux/scatterlist.h>
#include <asm/io.h>
+#include <asm/pat.h>
#include <asm/x86_init.h>
#ifdef __KERNEL__
@@ -102,6 +103,7 @@ int pcibios_set_irq_routing(struct pci_dev *dev, int pin, int irq);
#define HAVE_PCI_MMAP
+#define arch_can_pci_mmap_wc() pat_enabled()
extern int pci_mmap_page_range(struct pci_dev *dev, struct vm_area_struct *vma,
enum pci_mmap_state mmap_state,
int write_combine);
diff --git a/arch/xtensa/include/asm/pci.h b/arch/xtensa/include/asm/pci.h
index 5d6bd93..f106879 100644
--- a/arch/xtensa/include/asm/pci.h
+++ b/arch/xtensa/include/asm/pci.h
@@ -51,7 +51,11 @@ int pci_mmap_page_range(struct pci_dev *pdev, struct vm_area_struct *vma,
enum pci_mmap_state mmap_state, int write_combine);
/* Tell drivers/pci/proc.c that we have pci_mmap_page_range() */
-#define HAVE_PCI_MMAP 1
+#define HAVE_PCI_MMAP 1
+
+/* This was wrapped in #if 0 since the first merge of xtensa support...
+#define arch_can_pci_mmap_wc() 1
+*/
#endif /* __KERNEL__ */
diff --git a/arch/xtensa/kernel/pci.c b/arch/xtensa/kernel/pci.c
index b848cc3..c5944d3 100644
--- a/arch/xtensa/kernel/pci.c
+++ b/arch/xtensa/kernel/pci.c
@@ -345,7 +345,7 @@ __pci_mmap_set_pgprot(struct pci_dev *dev, struct vm_area_struct *vma,
/* Set to write-through */
prot = (prot & _PAGE_CA_MASK) | _PAGE_CA_WT;
-#if 0
+#ifdef arch_can_pci_mmap_wc
if (!write_combine)
prot |= _PAGE_WRITETHRU;
#endif
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 7ac258f..cf2c7d8 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -1210,10 +1210,12 @@ static int pci_create_resource_files(struct pci_dev *pdev)
continue;
retval = pci_create_attr(pdev, i, 0);
+#ifdef arch_can_pci_mmap_wc
/* for prefetchable resources, create a WC mappable file */
- if (!retval && pdev->resource[i].flags & IORESOURCE_PREFETCH)
+ if (!retval && arch_can_pci_mmap_wc() &&
+ pdev->resource[i].flags & IORESOURCE_PREFETCH)
retval = pci_create_attr(pdev, i, 1);
-
+#endif
if (retval) {
pci_remove_resource_files(pdev);
return retval;
diff --git a/drivers/pci/proc.c b/drivers/pci/proc.c
index dc8912e..c49be71 100644
--- a/drivers/pci/proc.c
+++ b/drivers/pci/proc.c
@@ -209,15 +209,18 @@ static long proc_bus_pci_ioctl(struct file *file, unsigned int cmd,
fpriv->mmap_state = pci_mmap_mem;
break;
+#ifdef arch_can_pci_mmap_wc
case PCIIOC_WRITE_COMBINE:
- if (arg)
- fpriv->write_combine = 1;
- else
- fpriv->write_combine = 0;
- break;
-
+ if (arch_can_pci_mmap_wc()) {
+ if (arg)
+ fpriv->write_combine = 1;
+ else
+ fpriv->write_combine = 0;
+ break;
+ }
+ /* If arch decided it can't, fall through... */
+#endif /* arch_can_pci_mmap_wc */
#endif /* HAVE_PCI_MMAP */
-
default:
ret = -EINVAL;
break;
--
2.9.3