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[PATCH v2 4/6] x86: Add clear_page_nocache

To: linux-mm@kvack.org
Subject: [PATCH v2 4/6] x86: Add clear_page_nocache
From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Date: Thu, 9 Aug 2012 18:03:01 +0300
Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org, Andi Kleen <ak@linux.intel.com>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Tim Chen <tim.c.chen@linux.intel.com>, Alex Shi <alex.shu@intel.com>, Jan Beulich <jbeulich@novell.com>, Robert Richter <robert.richter@amd.com>, Andy Lutomirski <luto@amacapital.net>, Andrew Morton <akpm@linux-foundation.org>, Andrea Arcangeli <aarcange@redhat.com>, Johannes Weiner <hannes@cmpxchg.org>, Hugh Dickins <hughd@google.com>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>, Mel Gorman <mgorman@suse.de>, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-mips@linux-mips.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org
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From: Andi Kleen <ak@linux.intel.com>

Add a cache avoiding version of clear_page. Straight forward integer variant
of the existing 64bit clear_page, for both 32bit and 64bit.

Also add the necessary glue for highmem including a layer that non cache
coherent architectures that use the virtual address for flushing can
hook in. This is not needed on x86 of course.

If an architecture wants to provide cache avoiding version of clear_page
it should to define ARCH_HAS_USER_NOCACHE to 1 and implement
clear_page_nocache() and clear_user_highpage_nocache().

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/include/asm/page.h          |    2 ++
 arch/x86/include/asm/string_32.h     |    5 +++++
 arch/x86/include/asm/string_64.h     |    5 +++++
 arch/x86/lib/Makefile                |    1 +
 arch/x86/lib/clear_page_nocache_32.S |   30 ++++++++++++++++++++++++++++++
 arch/x86/lib/clear_page_nocache_64.S |   29 +++++++++++++++++++++++++++++
 arch/x86/mm/fault.c                  |    7 +++++++
 7 files changed, 79 insertions(+), 0 deletions(-)
 create mode 100644 arch/x86/lib/clear_page_nocache_32.S
 create mode 100644 arch/x86/lib/clear_page_nocache_64.S

diff --git a/arch/x86/include/asm/page.h b/arch/x86/include/asm/page.h
index 8ca8283..aa83a1b 100644
--- a/arch/x86/include/asm/page.h
+++ b/arch/x86/include/asm/page.h
@@ -29,6 +29,8 @@ static inline void copy_user_page(void *to, void *from, 
unsigned long vaddr,
        copy_page(to, from);
 }
 
+void clear_user_highpage_nocache(struct page *page, unsigned long vaddr);
+
 #define __alloc_zeroed_user_highpage(movableflags, vma, vaddr) \
        alloc_page_vma(GFP_HIGHUSER | __GFP_ZERO | movableflags, vma, vaddr)
 #define __HAVE_ARCH_ALLOC_ZEROED_USER_HIGHPAGE
diff --git a/arch/x86/include/asm/string_32.h b/arch/x86/include/asm/string_32.h
index 3d3e835..3f2fbcf 100644
--- a/arch/x86/include/asm/string_32.h
+++ b/arch/x86/include/asm/string_32.h
@@ -3,6 +3,8 @@
 
 #ifdef __KERNEL__
 
+#include <linux/linkage.h>
+
 /* Let gcc decide whether to inline or use the out of line functions */
 
 #define __HAVE_ARCH_STRCPY
@@ -337,6 +339,9 @@ void *__constant_c_and_count_memset(void *s, unsigned long 
pattern,
 #define __HAVE_ARCH_MEMSCAN
 extern void *memscan(void *addr, int c, size_t size);
 
+#define ARCH_HAS_USER_NOCACHE 1
+asmlinkage void clear_page_nocache(void *page);
+
 #endif /* __KERNEL__ */
 
 #endif /* _ASM_X86_STRING_32_H */
diff --git a/arch/x86/include/asm/string_64.h b/arch/x86/include/asm/string_64.h
index 19e2c46..ca23d1d 100644
--- a/arch/x86/include/asm/string_64.h
+++ b/arch/x86/include/asm/string_64.h
@@ -3,6 +3,8 @@
 
 #ifdef __KERNEL__
 
+#include <linux/linkage.h>
+
 /* Written 2002 by Andi Kleen */
 
 /* Only used for special circumstances. Stolen from i386/string.h */
@@ -63,6 +65,9 @@ char *strcpy(char *dest, const char *src);
 char *strcat(char *dest, const char *src);
 int strcmp(const char *cs, const char *ct);
 
+#define ARCH_HAS_USER_NOCACHE 1
+asmlinkage void clear_page_nocache(void *page);
+
 #endif /* __KERNEL__ */
 
 #endif /* _ASM_X86_STRING_64_H */
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index b00f678..a8ad6dd 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -23,6 +23,7 @@ lib-y += memcpy_$(BITS).o
 lib-$(CONFIG_SMP) += rwlock.o
 lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem.o
 lib-$(CONFIG_INSTRUCTION_DECODER) += insn.o inat.o
+lib-y += clear_page_nocache_$(BITS).o
 
 obj-y += msr.o msr-reg.o msr-reg-export.o
 
diff --git a/arch/x86/lib/clear_page_nocache_32.S 
b/arch/x86/lib/clear_page_nocache_32.S
new file mode 100644
index 0000000..2394e0c
--- /dev/null
+++ b/arch/x86/lib/clear_page_nocache_32.S
@@ -0,0 +1,30 @@
+#include <linux/linkage.h>
+#include <asm/dwarf2.h>
+
+/*
+ * Zero a page avoiding the caches
+ * rdi page
+ */
+ENTRY(clear_page_nocache)
+       CFI_STARTPROC
+       mov    %eax,%edi
+       xorl   %eax,%eax
+       movl   $4096/64,%ecx
+       .p2align 4
+.Lloop:
+       decl    %ecx
+#define PUT(x) movnti %eax,x*8(%edi) ; movnti %eax,x*8+4(%edi)
+       PUT(0)
+       PUT(1)
+       PUT(2)
+       PUT(3)
+       PUT(4)
+       PUT(5)
+       PUT(6)
+       PUT(7)
+       lea     64(%edi),%edi
+       jnz     .Lloop
+       nop
+       ret
+       CFI_ENDPROC
+ENDPROC(clear_page_nocache)
diff --git a/arch/x86/lib/clear_page_nocache_64.S 
b/arch/x86/lib/clear_page_nocache_64.S
new file mode 100644
index 0000000..ee16d15
--- /dev/null
+++ b/arch/x86/lib/clear_page_nocache_64.S
@@ -0,0 +1,29 @@
+#include <linux/linkage.h>
+#include <asm/dwarf2.h>
+
+/*
+ * Zero a page avoiding the caches
+ * rdi page
+ */
+ENTRY(clear_page_nocache)
+       CFI_STARTPROC
+       xorl   %eax,%eax
+       movl   $4096/64,%ecx
+       .p2align 4
+.Lloop:
+       decl    %ecx
+#define PUT(x) movnti %rax,x*8(%rdi)
+       movnti %rax,(%rdi)
+       PUT(1)
+       PUT(2)
+       PUT(3)
+       PUT(4)
+       PUT(5)
+       PUT(6)
+       PUT(7)
+       leaq    64(%rdi),%rdi
+       jnz     .Lloop
+       nop
+       ret
+       CFI_ENDPROC
+ENDPROC(clear_page_nocache)
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 76dcd9d..20888b4 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1209,3 +1209,10 @@ good_area:
 
        up_read(&mm->mmap_sem);
 }
+
+void clear_user_highpage_nocache(struct page *page, unsigned long vaddr)
+{
+       void *p = kmap_atomic(page, KM_USER0);
+       clear_page_nocache(p);
+       kunmap_atomic(p);
+}
-- 
1.7.7.6


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