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Date: Sun, 31 May 2015 11:48:05 +0200
From: Borislav Petkov <bp@...en8.de>
To: LKML <linux-kernel@...r.kernel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Andy Lutomirski <luto@...capital.net>, arnd@...db.de,
Elliott@...com, hch@....de, hmh@....eng.br,
"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
jgross@...e.com, konrad.wilk@...cle.com,
linux-mm <linux-mm@...ck.org>, linux-nvdimm@...ts.01.org,
"Luis R. Rodriguez" <mcgrof@...e.com>, stefan.bader@...onical.com,
Thomas Gleixner <tglx@...utronix.de>,
Toshi Kani <toshi.kani@...com>, x86-ml <x86@...nel.org>,
yigal@...xistor.com
Subject: [PATCH 3/4] x86/pat: Emulate PAT when it is disabled
From: Borislav Petkov <bp@...e.de>
In the case when PAT is disabled on the command line with "nopat" or
when virtualization doesn't support PAT (correctly) - see
9d34cfdf4796 ("x86: Don't rely on VMWare emulating PAT MSR correctly").
we emulate it using the PWT and PCD cache attribute bits. Get rid of
boot_pat_state while at it.
Based on a conglomerate patch from Toshi Kani.
Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: arnd@...db.de
Cc: Elliott@...com
Cc: hch@....de
Cc: hmh@....eng.br
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: jgross@...e.com
Cc: konrad.wilk@...cle.com
Cc: linux-mm <linux-mm@...ck.org>
Cc: linux-nvdimm@...ts.01.org
Cc: Luis R. Rodriguez <mcgrof@...e.com>
Cc: stefan.bader@...onical.com
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Toshi Kani <toshi.kani@...com>
Cc: x86-ml <x86@...nel.org>
Cc: yigal@...xistor.com
---
arch/x86/mm/init.c | 6 ++---
arch/x86/mm/pat.c | 72 +++++++++++++++++++++++++++++++++++++-----------------
2 files changed, 52 insertions(+), 26 deletions(-)
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index 1d553186c434..8533b46e6bee 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -40,7 +40,7 @@
*/
uint16_t __cachemode2pte_tbl[_PAGE_CACHE_MODE_NUM] = {
[_PAGE_CACHE_MODE_WB ] = 0 | 0 ,
- [_PAGE_CACHE_MODE_WC ] = _PAGE_PWT | 0 ,
+ [_PAGE_CACHE_MODE_WC ] = 0 | _PAGE_PCD,
[_PAGE_CACHE_MODE_UC_MINUS] = 0 | _PAGE_PCD,
[_PAGE_CACHE_MODE_UC ] = _PAGE_PWT | _PAGE_PCD,
[_PAGE_CACHE_MODE_WT ] = 0 | _PAGE_PCD,
@@ -50,11 +50,11 @@ EXPORT_SYMBOL(__cachemode2pte_tbl);
uint8_t __pte2cachemode_tbl[8] = {
[__pte2cm_idx( 0 | 0 | 0 )] = _PAGE_CACHE_MODE_WB,
- [__pte2cm_idx(_PAGE_PWT | 0 | 0 )] = _PAGE_CACHE_MODE_WC,
+ [__pte2cm_idx(_PAGE_PWT | 0 | 0 )] = _PAGE_CACHE_MODE_UC_MINUS,
[__pte2cm_idx( 0 | _PAGE_PCD | 0 )] = _PAGE_CACHE_MODE_UC_MINUS,
[__pte2cm_idx(_PAGE_PWT | _PAGE_PCD | 0 )] = _PAGE_CACHE_MODE_UC,
[__pte2cm_idx( 0 | 0 | _PAGE_PAT)] = _PAGE_CACHE_MODE_WB,
- [__pte2cm_idx(_PAGE_PWT | 0 | _PAGE_PAT)] = _PAGE_CACHE_MODE_WC,
+ [__pte2cm_idx(_PAGE_PWT | 0 | _PAGE_PAT)] = _PAGE_CACHE_MODE_UC_MINUS,
[__pte2cm_idx(0 | _PAGE_PCD | _PAGE_PAT)] = _PAGE_CACHE_MODE_UC_MINUS,
[__pte2cm_idx(_PAGE_PWT | _PAGE_PCD | _PAGE_PAT)] = _PAGE_CACHE_MODE_UC,
};
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 4d28759f5a1a..62171cb2b0cb 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -68,8 +68,6 @@ static int __init pat_debug_setup(char *str)
}
__setup("debugpat", pat_debug_setup);
-static u64 __read_mostly boot_pat_state;
-
#ifdef CONFIG_X86_PAT
/*
* X86 PAT uses page flags WC and Uncached together to keep track of
@@ -178,6 +176,7 @@ static void pat_bsp_init(u64 pat)
{
enum page_cache_mode cache;
char pat_msg[33];
+ u64 tmp_pat;
int i;
if (!cpu_has_pat) {
@@ -185,14 +184,18 @@ static void pat_bsp_init(u64 pat)
return;
}
- rdmsrl(MSR_IA32_CR_PAT, boot_pat_state);
- if (!boot_pat_state) {
+ if (!pat_enabled())
+ goto done;
+
+ rdmsrl(MSR_IA32_CR_PAT, tmp_pat);
+ if (!tmp_pat) {
pat_disable("PAT MSR is 0, disabled.");
return;
}
wrmsrl(MSR_IA32_CR_PAT, pat);
+done:
pat_msg[32] = 0;
/*
@@ -209,6 +212,9 @@ static void pat_bsp_init(u64 pat)
static void pat_ap_init(u64 pat)
{
+ if (!pat_enabled())
+ return;
+
if (!cpu_has_pat) {
/*
* If this happens we are on a secondary CPU, but switched to
@@ -224,25 +230,45 @@ void pat_init(void)
{
u64 pat;
- if (!pat_enabled())
- return;
-
- /*
- * Set PWT to Write-Combining. All other bits stay the same:
- *
- * PTE encoding used in Linux:
- * PAT
- * |PCD
- * ||PWT
- * |||
- * 000 WB _PAGE_CACHE_WB
- * 001 WC _PAGE_CACHE_WC
- * 010 UC- _PAGE_CACHE_UC_MINUS
- * 011 UC _PAGE_CACHE_UC
- * PAT bit unused
- */
- pat = PAT(0, WB) | PAT(1, WC) | PAT(2, UC_MINUS) | PAT(3, UC) |
- PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, UC);
+ if (!pat_enabled()) {
+ /*
+ * No PAT. Emulate the PAT table that corresponds to the two
+ * cache bits, PWT (Write Through) and PCD (Cache Disable). This
+ * setup is the same as the BIOS default setup when the system
+ * has PAT but the "nopat" boot option has been specified. This
+ * emulated PAT table is used when MSR_IA32_CR_PAT returns 0.
+ *
+ * PTE encoding used:
+ *
+ * PCD
+ * |PWT PAT
+ * || slot
+ * 00 0 WB : _PAGE_CACHE_MODE_WB
+ * 01 1 WT : _PAGE_CACHE_MODE_WT
+ * 10 2 UC-: _PAGE_CACHE_MODE_UC_MINUS
+ * 11 3 UC : _PAGE_CACHE_MODE_UC
+ *
+ * NOTE: When WC or WP is used, it is redirected to UC- per
+ * the default setup in __cachemode2pte_tbl[].
+ */
+ pat = PAT(0, WB) | PAT(1, WT) | PAT(2, UC_MINUS) | PAT(3, UC) |
+ PAT(4, WB) | PAT(5, WT) | PAT(6, UC_MINUS) | PAT(7, UC);
+ } else {
+ /*
+ * PTE encoding used in Linux:
+ * PAT
+ * |PCD
+ * ||PWT
+ * |||
+ * 000 WB _PAGE_CACHE_WB
+ * 001 WC _PAGE_CACHE_WC
+ * 010 UC- _PAGE_CACHE_UC_MINUS
+ * 011 UC _PAGE_CACHE_UC
+ * PAT bit unused
+ */
+ pat = PAT(0, WB) | PAT(1, WC) | PAT(2, UC_MINUS) | PAT(3, UC) |
+ PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, UC);
+ }
if (!boot_cpu_done) {
pat_bsp_init(pat);
--
2.3.5
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