linux-kernel - [RFC PATCH 6/7] x86, mm: Support huge I/O mappings on x86

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Date:	Mon, 26 Jan 2015 16:13:28 -0700
From:	Toshi Kani <toshi.kani@...com>
To:	akpm@...ux-foundation.org, hpa@...or.com, tglx@...utronix.de,
	mingo@...hat.com, arnd@...db.de, linux-mm@...ck.org
Cc:	x86@...nel.org, linux-kernel@...r.kernel.org,
	Toshi Kani <toshi.kani@...com>
Subject: [RFC PATCH 6/7] x86, mm: Support huge I/O mappings on x86

Implement huge I/O mapping capability interfaces on x86.

Also define IOREMAP_MAX_ORDER to the size of PUD or PMD on x86.
When IOREMAP_MAX_ORDER is not defined on x86, it will be defined
to the default value in <linux/vmalloc.h>.

Signed-off-by: Toshi Kani <toshi.kani@...com>
---
 arch/x86/include/asm/page_types.h |    8 ++++++++
 arch/x86/mm/ioremap.c             |   16 ++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/arch/x86/include/asm/page_types.h b/arch/x86/include/asm/page_types.h
index f97fbe3..debbfff 100644
--- a/arch/x86/include/asm/page_types.h
+++ b/arch/x86/include/asm/page_types.h
@@ -38,6 +38,14 @@
 
 #define __START_KERNEL		(__START_KERNEL_map + __PHYSICAL_START)
 
+#ifdef CONFIG_HUGE_IOMAP
+#ifdef CONFIG_X86_64
+#define IOREMAP_MAX_ORDER       (PUD_SHIFT)
+#elif defined(PMD_SHIFT)
+#define IOREMAP_MAX_ORDER       (PMD_SHIFT)
+#endif
+#endif  /* CONFIG_HUGE_IOMAP */
+
 #ifdef CONFIG_X86_64
 #include <asm/page_64_types.h>
 #else
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index fdf617c..ef32bec 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -326,6 +326,22 @@ void iounmap(volatile void __iomem *addr)
 }
 EXPORT_SYMBOL(iounmap);
 
+#ifdef CONFIG_HUGE_IOMAP
+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;
+}
+#endif	/* CONFIG_HUGE_IOMAP */
+
 /*
  * Convert a physical pointer to a virtual kernel pointer for /dev/mem
  * access
--
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