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From: Toshi Kani <toshi.kani@hp.com>
To: hpa@zytor.com, tglx@linutronix.de, mingo@redhat.com,
	akpm@linux-foundation.org, arnd@arndb.de
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	jgross@suse.com, stefan.bader@canonical.com, luto@amacapital.net,
	hmh@hmh.eng.br, yigal@plexistor.com, konrad.wilk@oracle.com,
	Elliott@hp.com, Toshi Kani <toshi.kani@hp.com>
Subject: [PATCH v8 6/7] x86, mm, asm: Add WT support to set_page_memtype()
Date: Tue, 24 Feb 2015 17:15:00 -0700	[thread overview]
Message-ID: <1424823301-30927-7-git-send-email-toshi.kani@hp.com> (raw)
In-Reply-To: <1424823301-30927-1-git-send-email-toshi.kani@hp.com>

As set_memory_wb() calls set_page_memtype() with -1, _PGMT_DEFAULT is
solely used for tracking the WB type.  _PGMT_WB is defined but unused.
Hence, this patch renames _PGMT_DEFAULT to _PGMT_WB to clarify its
usage, and releases the slot used by _PGMT_WB before.  As a result,
set_memory_wb() is changed to call set_page_memtype() with _PGMT_WB,
and get_page_memtype() returns _PAGE_CACHE_MODE_WB for _PGMT_WB.

This patch then defines _PGMT_WT to the released slot.  This enables
set_page_memtype() to track the WT type.

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
---
 arch/x86/mm/pat.c |   48 +++++++++++++++++++++---------------------------
 1 file changed, 21 insertions(+), 27 deletions(-)

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index db3cc89..cfb14ac 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -69,18 +69,18 @@ static u64 __read_mostly boot_pat_state;
 
 #ifdef CONFIG_X86_PAT
 /*
- * X86 PAT uses page flags WC and Uncached together to keep track of
- * memory type of pages that have backing page struct. X86 PAT supports 3
- * different memory types, _PAGE_CACHE_MODE_WB, _PAGE_CACHE_MODE_WC and
- * _PAGE_CACHE_MODE_UC_MINUS and fourth state where page's memory type has not
- * been changed from its default (value of -1 used to denote this).
+ * X86 PAT uses page flags arch_1 and uncached together to keep track of
+ * memory type of pages that have backing page struct. X86 PAT supports 4
+ * different memory types, _PAGE_CACHE_MODE_WT, _PAGE_CACHE_MODE_WC,
+ * _PAGE_CACHE_MODE_UC_MINUS and _PAGE_CACHE_MODE_WB where page's memory
+ * type has not been changed from its default.
  * Note we do not support _PAGE_CACHE_MODE_UC here.
  */
 
-#define _PGMT_DEFAULT		0
+#define _PGMT_WB		0	/* default */
 #define _PGMT_WC		(1UL << PG_arch_1)
 #define _PGMT_UC_MINUS		(1UL << PG_uncached)
-#define _PGMT_WB		(1UL << PG_uncached | 1UL << PG_arch_1)
+#define _PGMT_WT		(1UL << PG_uncached | 1UL << PG_arch_1)
 #define _PGMT_MASK		(1UL << PG_uncached | 1UL << PG_arch_1)
 #define _PGMT_CLEAR_MASK	(~_PGMT_MASK)
 
@@ -88,14 +88,14 @@ static inline enum page_cache_mode get_page_memtype(struct page *pg)
 {
 	unsigned long pg_flags = pg->flags & _PGMT_MASK;
 
-	if (pg_flags == _PGMT_DEFAULT)
-		return -1;
+	if (pg_flags == _PGMT_WB)
+		return _PAGE_CACHE_MODE_WB;
 	else if (pg_flags == _PGMT_WC)
 		return _PAGE_CACHE_MODE_WC;
 	else if (pg_flags == _PGMT_UC_MINUS)
 		return _PAGE_CACHE_MODE_UC_MINUS;
 	else
-		return _PAGE_CACHE_MODE_WB;
+		return _PAGE_CACHE_MODE_WT;
 }
 
 static inline void set_page_memtype(struct page *pg,
@@ -112,11 +112,12 @@ static inline void set_page_memtype(struct page *pg,
 	case _PAGE_CACHE_MODE_UC_MINUS:
 		memtype_flags = _PGMT_UC_MINUS;
 		break;
-	case _PAGE_CACHE_MODE_WB:
-		memtype_flags = _PGMT_WB;
+	case _PAGE_CACHE_MODE_WT:
+		memtype_flags = _PGMT_WT;
 		break;
+	case _PAGE_CACHE_MODE_WB:
 	default:
-		memtype_flags = _PGMT_DEFAULT;
+		memtype_flags = _PGMT_WB;	/* default */
 		break;
 	}
 
@@ -391,8 +392,9 @@ static int pat_pagerange_is_ram(resource_size_t start, resource_size_t end)
 
 /*
  * For RAM pages, we use page flags to mark the pages with appropriate type.
- * The page flags are limited to three types, WB, WC and UC-.
- * WT and WP requests fail with -EINVAL, and UC gets redirected to UC-.
+ * The page flags are limited to four types, WB (default), WC, WT and UC-.
+ * WP request fails with -EINVAL, and UC gets redirected to UC-.
+ * A new memtype can only be set to the default memtype WB.
  * Here we do two pass:
  * - Find the memtype of all the pages in the range, look for any conflicts
  * - In case of no conflicts, set the new memtype for pages in the range
@@ -404,8 +406,7 @@ static int reserve_ram_pages_type(u64 start, u64 end,
 	struct page *page;
 	u64 pfn;
 
-	if ((req_type == _PAGE_CACHE_MODE_WT) ||
-	    (req_type == _PAGE_CACHE_MODE_WP)) {
+	if (req_type == _PAGE_CACHE_MODE_WP) {
 		if (new_type)
 			*new_type = _PAGE_CACHE_MODE_UC_MINUS;
 		return -EINVAL;
@@ -422,7 +423,7 @@ static int reserve_ram_pages_type(u64 start, u64 end,
 
 		page = pfn_to_page(pfn);
 		type = get_page_memtype(page);
-		if (type != -1) {
+		if (type != _PAGE_CACHE_MODE_WB) {
 			pr_info("reserve_ram_pages_type failed [mem %#010Lx-%#010Lx], track 0x%x, req 0x%x\n",
 				start, end - 1, type, req_type);
 			if (new_type)
@@ -449,7 +450,7 @@ static int free_ram_pages_type(u64 start, u64 end)
 
 	for (pfn = (start >> PAGE_SHIFT); pfn < (end >> PAGE_SHIFT); ++pfn) {
 		page = pfn_to_page(pfn);
-		set_page_memtype(page, -1);
+		set_page_memtype(page, _PAGE_CACHE_MODE_WB);
 	}
 	return 0;
 }
@@ -589,7 +590,7 @@ int free_memtype(u64 start, u64 end)
  * Only to be called when PAT is enabled
  *
  * Returns _PAGE_CACHE_MODE_WB, _PAGE_CACHE_MODE_WC, _PAGE_CACHE_MODE_UC_MINUS
- * or _PAGE_CACHE_MODE_UC
+ * or _PAGE_CACHE_MODE_WT.
  */
 static enum page_cache_mode lookup_memtype(u64 paddr)
 {
@@ -603,13 +604,6 @@ static enum page_cache_mode lookup_memtype(u64 paddr)
 		struct page *page;
 		page = pfn_to_page(paddr >> PAGE_SHIFT);
 		rettype = get_page_memtype(page);
-		/*
-		 * -1 from get_page_memtype() implies RAM page is in its
-		 * default state and not reserved, and hence of type WB
-		 */
-		if (rettype == -1)
-			rettype = _PAGE_CACHE_MODE_WB;
-
 		return rettype;
 	}
 

  parent reply	other threads:[~2015-02-25  0:15 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-02-25  0:14 [PATCH v8 0/7] Support Write-Through mapping on x86 Toshi Kani
2015-02-25  0:14 ` [PATCH v8 1/7] x86, mm, pat: Set WT to PA7 slot of PAT MSR Toshi Kani
2015-02-25  0:14 ` [PATCH v8 2/7] x86, mm, pat: Change reserve_memtype() to handle WT Toshi Kani
2015-02-25  0:14 ` [PATCH v8 3/7] x86, mm, asm-gen: Add ioremap_wt() for WT Toshi Kani
2015-02-25  0:14 ` [PATCH v8 4/7] x86, mm, pat: Add pgprot_writethrough() " Toshi Kani
2015-02-25  0:14 ` [PATCH v8 5/7] x86, mm, pat: Refactor !pat_enabled handling Toshi Kani
2015-02-25  0:15 ` Toshi Kani [this message]
2015-02-25  0:15 ` [PATCH v8 7/7] x86, mm: Add set_memory_wt() for WT Toshi Kani
2015-02-25  7:22   ` Ingo Molnar
2015-02-25 15:20     ` Toshi Kani
2015-02-26 11:30       ` Ingo Molnar
2015-02-26 14:44         ` Toshi Kani
2015-03-04 18:27           ` Toshi Kani

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