[PATCH v3 5/6] x86, mm: Support huge I/O mapping capability I/F

[Toshi Kani <toshi.kani@hp.com>]

This patch implements huge I/O mapping capability interfaces
for ioremap() on x86.

IOREMAP_MAX_ORDER is defined to PUD_SHIFT on x86/64 and
PMD_SHIFT on x86/32, which overrides the default value
defined in <linux/vmalloc.h>.

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
---
 arch/x86/include/asm/page_types.h |    2 ++
 arch/x86/mm/ioremap.c             |   23 +++++++++++++++++++++--
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/page_types.h b/arch/x86/include/asm/page_types.h
index 95e11f7..b526093 100644
--- a/arch/x86/include/asm/page_types.h
+++ b/arch/x86/include/asm/page_types.h
@@ -40,8 +40,10 @@
 
 #ifdef CONFIG_X86_64
 #include <asm/page_64_types.h>
+#define IOREMAP_MAX_ORDER       (PUD_SHIFT)
 #else
 #include <asm/page_32_types.h>
+#define IOREMAP_MAX_ORDER       (PMD_SHIFT)
 #endif	/* CONFIG_X86_64 */
 
 #ifndef __ASSEMBLY__
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index fdf617c..5ead4d6 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -67,8 +67,13 @@ static int __ioremap_check_ram(unsigned long start_pfn, unsigned long nr_pages,
 
 /*
  * Remap an arbitrary physical address space into the kernel virtual
- * address space. Needed when the kernel wants to access high addresses
- * directly.
+ * address space. It transparently creates kernel huge I/O mapping when
+ * the physical address is aligned by a huge page size (1GB or 2MB) and
+ * the requested size is at least the huge page size.
+ *
+ * NOTE: MTRRs can override PAT memory types with a 4KB granularity.
+ * Therefore, the mapping code falls back to use a smaller page toward 4KB
+ * when a mapping range is covered by non-WB type of MTRRs.
  *
  * NOTE! We need to allow non-page-aligned mappings too: we will obviously
  * have to convert them into an offset in a page-aligned mapping, but the
@@ -326,6 +331,20 @@ void iounmap(volatile void __iomem *addr)
 }
 EXPORT_SYMBOL(iounmap);
 
+int arch_ioremap_pud_supported(void)
+{
+#ifdef CONFIG_X86_64
+	return cpu_has_gbpages;
+#else
+	return 0;
+#endif
+}
+
+int arch_ioremap_pmd_supported(void)
+{
+	return cpu_has_pse;
+}
+
 /*
  * Convert a physical pointer to a virtual kernel pointer for /dev/mem
  * access

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