linux-kernel - [tip:x86/mm] x86/xen, pat: Remove PAT table init code from Xen

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Date:	Tue, 29 Mar 2016 03:39:58 -0700
From:	tip-bot for Toshi Kani <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	toshi.kani@...com, tglx@...utronix.de, bp@...en8.de,
	luto@...capital.net, bp@...e.de, hpa@...or.com,
	dvlasenk@...hat.com, toshi.kani@....com, mingo@...nel.org,
	jgross@...e.com, konrad.wilk@...cle.com,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, peterz@...radead.org,
	mcgrof@...e.com, brgerst@...il.com
Subject: [tip:x86/mm] x86/xen, pat: Remove PAT table init code from Xen

Commit-ID:  88ba281108ed0c25c9d292b48bd3f272fcb90dd0
Gitweb:     http://git.kernel.org/tip/88ba281108ed0c25c9d292b48bd3f272fcb90dd0
Author:     Toshi Kani <toshi.kani@....com>
AuthorDate: Wed, 23 Mar 2016 15:42:02 -0600
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 29 Mar 2016 12:23:27 +0200

x86/xen, pat: Remove PAT table init code from Xen

Xen supports PAT without MTRRs for its guests.  In order to
enable WC attribute, it was necessary for xen_start_kernel()
to call pat_init_cache_modes() to update PAT table before
starting guest kernel.

Now that the kernel initializes PAT table to the BIOS handoff
state when MTRR is disabled, this Xen-specific PAT init code
is no longer necessary.  Delete it from xen_start_kernel().

Also change __init_cache_modes() to a static function since
PAT table should not be tweaked by other modules.

Signed-off-by: Toshi Kani <toshi.kani@....com>
Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: Juergen Gross <jgross@...e.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Borislav Petkov <bp@...e.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Luis R. Rodriguez <mcgrof@...e.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Toshi Kani <toshi.kani@...com>
Cc: elliott@....com
Cc: paul.gortmaker@...driver.com
Cc: xen-devel@...ts.xenproject.org
Link: http://lkml.kernel.org/r/1458769323-24491-7-git-send-email-toshi.kani@hpe.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/include/asm/pat.h | 1 -
 arch/x86/mm/pat.c          | 2 +-
 arch/x86/xen/enlighten.c   | 9 ---------
 3 files changed, 1 insertion(+), 11 deletions(-)

diff --git a/arch/x86/include/asm/pat.h b/arch/x86/include/asm/pat.h
index 0ad356c..0b1ff4c 100644
--- a/arch/x86/include/asm/pat.h
+++ b/arch/x86/include/asm/pat.h
@@ -7,7 +7,6 @@
 bool pat_enabled(void);
 void pat_disable(const char *reason);
 extern void pat_init(void);
-void __init_cache_modes(u64);
 
 extern int reserve_memtype(u64 start, u64 end,
 		enum page_cache_mode req_pcm, enum page_cache_mode *ret_pcm);
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 59ec038..c4c3ddc 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -192,7 +192,7 @@ static enum page_cache_mode pat_get_cache_mode(unsigned pat_val, char *msg)
  * configuration.
  * Using lower indices is preferred, so we start with highest index.
  */
-void __init_cache_modes(u64 pat)
+static void __init_cache_modes(u64 pat)
 {
 	enum page_cache_mode cache;
 	char pat_msg[33];
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index c469a7c..d8cca75 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -75,7 +75,6 @@
 #include <asm/mach_traps.h>
 #include <asm/mwait.h>
 #include <asm/pci_x86.h>
-#include <asm/pat.h>
 #include <asm/cpu.h>
 
 #ifdef CONFIG_ACPI
@@ -1511,7 +1510,6 @@ asmlinkage __visible void __init xen_start_kernel(void)
 {
 	struct physdev_set_iopl set_iopl;
 	unsigned long initrd_start = 0;
-	u64 pat;
 	int rc;
 
 	if (!xen_start_info)
@@ -1618,13 +1616,6 @@ asmlinkage __visible void __init xen_start_kernel(void)
 				   xen_start_info->nr_pages);
 	xen_reserve_special_pages();
 
-	/*
-	 * Modify the cache mode translation tables to match Xen's PAT
-	 * configuration.
-	 */
-	rdmsrl(MSR_IA32_CR_PAT, pat);
-	__init_cache_modes(pat);
-
 	/* keep using Xen gdt for now; no urgent need to change it */
 
 #ifdef CONFIG_X86_32