[Xen-devel] [PATCH 4.6 28/56] x86/xen, pat: Remove PAT table init code from Xen

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

4.6-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Toshi Kani <toshi.kani@xxxxxxx>

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.

Signed-off-by: Toshi Kani <toshi.kani@xxxxxxx>
Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Acked-by: Juergen Gross <jgross@xxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Luis R. Rodriguez <mcgrof@xxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Toshi Kani <toshi.kani@xxxxxx>
Cc: elliott@xxxxxxx
Cc: paul.gortmaker@xxxxxxxxxxxxx
Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
Link: 
http://lkml.kernel.org/r/1458769323-24491-7-git-send-email-toshi.kani@xxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 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(-)

--- 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);
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -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];
--- 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_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



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