[v2,4/9] x86/clear_page: extend clear_page*() for multi-page clearing

Commit Message

Ankur Arora Aug. 30, 2023, 6:49 p.m. UTC

clear_page*() variants now take a page-aligned length parameter and
clear the whole region.

Rename to clear_pages*().

Signed-off-by: Ankur Arora <[e-mail]>
---
 arch/x86/include/asm/page_64.h | 20 +++++++------
 arch/x86/lib/clear_page_64.S   | 52 +++++++++++++++++++++++++---------
 2 files changed, 49 insertions(+), 23 deletions(-)

Comments

Matthew Wilcox Sept. 8, 2023, 1:11 p.m. UTC | #1

On Wed, Aug 30, 2023 at 11:49:53AM -0700, Ankur Arora wrote:
> -void clear_page_orig(void *page);
> -void clear_page_rep(void *page);
> -void clear_page_erms(void *page);
> +void clear_pages_orig(void *page, unsigned int length);
> +void clear_pages_rep(void *page, unsigned int length);
> +void clear_pages_erms(void *page, unsigned int length);

Maybe make this size_t so we know it's a byte count rather than being
some other unit of length?

Patch

diff --git a/arch/x86/include/asm/page_64.h b/arch/x86/include/asm/page_64.h
index cc6b8e087192..56f9adf0e892 100644
--- a/arch/x86/include/asm/page_64.h
+++ b/arch/x86/include/asm/page_64.h
@@ -39,22 +39,24 @@  extern unsigned long __phys_addr_symbol(unsigned long);
 
 #define __phys_reloc_hide(x)	(x)
 
-void clear_page_orig(void *page);
-void clear_page_rep(void *page);
-void clear_page_erms(void *page);
+void clear_pages_orig(void *page, unsigned int length);
+void clear_pages_rep(void *page, unsigned int length);
+void clear_pages_erms(void *page, unsigned int length);
 
 static inline void clear_page(void *page)
 {
+	unsigned int length = PAGE_SIZE;
 	/*
-	 * Clean up KMSAN metadata for the page being cleared. The assembly call
+	 * Clean up KMSAN metadata for the pages being cleared. The assembly call
 	 * below clobbers @page, so we perform unpoisoning before it.
 	 */
-	kmsan_unpoison_memory(page, PAGE_SIZE);
-	alternative_call_2(clear_page_orig,
-			   clear_page_rep, X86_FEATURE_REP_GOOD,
-			   clear_page_erms, X86_FEATURE_ERMS,
+	kmsan_unpoison_memory(page, length);
+
+	alternative_call_2(clear_pages_orig,
+			   clear_pages_rep, X86_FEATURE_REP_GOOD,
+			   clear_pages_erms, X86_FEATURE_ERMS,
 			   "=D" (page),
-			   "0" (page)
+			   "0" (page), "S" (length)
 			   : "cc", "memory", "rax", "rcx");
 }
 
diff --git a/arch/x86/lib/clear_page_64.S b/arch/x86/lib/clear_page_64.S
index f74a3e704a1c..58cb1d6355a7 100644
--- a/arch/x86/lib/clear_page_64.S
+++ b/arch/x86/lib/clear_page_64.S
@@ -11,20 +11,35 @@ 
  */
 
 /*
- * Zero a page.
- * %rdi	- page
+ * Zero kernel page aligned region.
+ *
+ * Input:
+ * %rdi	- destination
+ * %esi	- length
+ *
+ * Clobbers: %rax, %rcx
  */
-SYM_FUNC_START(clear_page_rep)
-	movl $4096/8,%ecx
+SYM_FUNC_START(clear_pages_rep)
+	movl %esi, %ecx
 	xorl %eax,%eax
+	shrl $3,%ecx
 	rep stosq
 	RET
-SYM_FUNC_END(clear_page_rep)
-EXPORT_SYMBOL_GPL(clear_page_rep)
+SYM_FUNC_END(clear_pages_rep)
+EXPORT_SYMBOL_GPL(clear_pages_rep)
 
-SYM_FUNC_START(clear_page_orig)
+/*
+ * Original page zeroing loop.
+ * Input:
+ * %rdi	- destination
+ * %esi	- length
+ *
+ * Clobbers: %rax, %rcx, %rflags
+ */
+SYM_FUNC_START(clear_pages_orig)
+	movl   %esi, %ecx
 	xorl   %eax,%eax
-	movl   $4096/64,%ecx
+	shrl   $6,%ecx
 	.p2align 4
 .Lloop:
 	decl	%ecx
@@ -41,16 +56,25 @@  SYM_FUNC_START(clear_page_orig)
 	jnz	.Lloop
 	nop
 	RET
-SYM_FUNC_END(clear_page_orig)
-EXPORT_SYMBOL_GPL(clear_page_orig)
+SYM_FUNC_END(clear_pages_orig)
+EXPORT_SYMBOL_GPL(clear_pages_orig)
 
-SYM_FUNC_START(clear_page_erms)
-	movl $4096,%ecx
+/*
+ * Zero kernel page aligned region.
+ *
+ * Input:
+ * %rdi	- destination
+ * %esi	- length
+ *
+ * Clobbers: %rax, %rcx
+ */
+SYM_FUNC_START(clear_pages_erms)
+	movl %esi, %ecx
 	xorl %eax,%eax
 	rep stosb
 	RET
-SYM_FUNC_END(clear_page_erms)
-EXPORT_SYMBOL_GPL(clear_page_erms)
+SYM_FUNC_END(clear_pages_erms)
+EXPORT_SYMBOL_GPL(clear_pages_erms)
 
 /*
  * Default clear user-space.