x86, hotplug: Fix powersavings with offlined cores on AMD

Upstream commits: 93789b32dbf355e70f18b17a82e8661677a7f7fb,
	 1c9d16e35911090dee3f9313e6af13af623d66ee

ea53069231f9317062910d6e772cca4ce93de8c8 made a CPU use monitor/mwait
when offline. This is not the optimal choice for AMD wrt to powersavings
and we'd prefer our cores to halt (i.e. enter C1) instead. For this, the
same selection whether to use monitor/mwait has to be used as when we
select the idle routine for the machine.

With this patch, offlining cores 1-5 on a X6 machine allows core0 to
boost again.

[ hpa: putting this in urgent since it is a (power) regression fix ]

Reported-by: Andreas Herrmann <andreas.herrmann3@amd.com>
Cc: H. Peter Anvin <hpa@linux.intel.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Venkatesh Pallipadi <venki@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.hl>
Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
LKML-Reference: <1295534572-10730-1-git-send-email-bp@amd64.org>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h
index 4fab24de26b18404069994b908c79d3e4e481c50..4564c8e28a33562a347066c4e87b5ec09a01e497 100644 (file)
--- a/arch/x86/include/asm/cpu.h
+++ b/arch/x86/include/asm/cpu.h
@@ -32,5 +32,6 @@ extern void arch_unregister_cpu(int);
 
 DECLARE_PER_CPU(int, cpu_state);
 
+int mwait_usable(const struct cpuinfo_x86 *);
 
 #endif /* _ASM_X86_CPU_H */

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 2502aafeeb3de8b5e3835d1a4f22a73ac132a423..12d4bf11b4106042715521ab38d708c0ec61c886 100644 (file)
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -14,6 +14,7 @@
 #include <linux/utsname.h>
 #include <trace/events/power.h>
 #include <linux/hw_breakpoint.h>
+#include <asm/cpu.h>
 #include <asm/system.h>
 #include <asm/apic.h>
 #include <asm/syscalls.h>
@@ -509,13 +510,13 @@ static void poll_idle(void)
  *
  * idle=mwait overrides this decision and forces the usage of mwait.
  */
-static int __cpuinitdata force_mwait;
+static int force_mwait;
 
 #define MWAIT_INFO                     0x05
 #define MWAIT_ECX_EXTENDED_INFO                0x01
 #define MWAIT_EDX_C1                   0xf0
 
-static int __cpuinit mwait_usable(const struct cpuinfo_x86 *c)
+int mwait_usable(const struct cpuinfo_x86 *c)
 {
        u32 eax, ebx, ecx, edx;
 

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 083e99d1b7df2aba236563467f47ebb21a09943d..d8fd571d57bd35c95e08c878e5aa74685e695a9f 100644 (file)
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1396,8 +1396,9 @@ static inline void mwait_play_dead(void)
        unsigned int highest_subcstate = 0;
        int i;
        void *mwait_ptr;
+       struct cpuinfo_x86 *c = &current_cpu_data;
 
-       if (!cpu_has(&current_cpu_data, X86_FEATURE_MWAIT))
+       if (!(cpu_has(c, X86_FEATURE_MWAIT) && mwait_usable(c)))
                return;
        if (!cpu_has(&current_cpu_data, X86_FEATURE_CLFLSH))
                return;