Patch "x86/xen, pat: Remove PAT table init code from Xen" has been added to the 4.6-stable tree

This is a note to let you know that I've just added the patch titled

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

to the 4.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
x86-xen-pat-remove-pat-table-init-code-from-xen.patch
and it can be found in the queue-4.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Toshi Kani <[email protected]>
Date: Wed, 23 Mar 2016 15:42:02 -0600
Subject: x86/xen, pat: Remove PAT table init code from Xen

From: Toshi Kani <[email protected]>

commit 88ba281108ed0c25c9d292b48bd3f272fcb90dd0 upstream.

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.

---
 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(-)

@@ -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);

@@ -192,7 +192,7 @@ static enum page_cache_mode pat_get_cach
  * 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];

@@ -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_sta
 {
 	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_sta
 				   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

Patches currently in stable-queue which might be from [email protected] are

queue-4.6/x86-mm-pat-replace-cpu_has_pat-with-boot_cpu_has.patch queue-4.6/x86-mtrr-fix-xorg-crashes-in-qemu-sessions.patch queue-4.6/libnvdimm-pfn-dax-fix-initialization-vs-autodetect-for-mode-alignment.patch queue-4.6/x86-mm-pat-add-support-of-non-default-pat-msr-setting.patch queue-4.6/x86-xen-pat-remove-pat-table-init-code-from-xen.patch queue-4.6/x86-mtrr-fix-pat-init-handling-when-mtrr-is-disabled.patch queue-4.6/x86-mm-pat-add-pat_disable-interface.patch queue-4.6/x86-mm-pat-fix-bug_on-in-mmap_mem-on-qemu-i386.patch queue-4.6/x86-pat-document-the-pat-initialization-sequence.patch