RE: [Xen-devel] [PATCH]ACPI: re-enable mwait for xen cpuidle

["Wei, Gang" <gang.wei@xxxxxxxxx>]

The 3rd choice: don't clear MWAIT feature in xen. This should be the best 
choice.

Jimmy

X86: re-enable mwait for xen cpuidle

Xen hypervisor doesn't export mwait feature to dom0, but latest Linux kernel
start to check this feature while initializing _PDC object. Pass the MWAIT
feature to dom0 to let dom0 got & pass to xen correct C state info.

Signed-off-by: Wei Gang <gang.wei@xxxxxxxxx>

diff -r 537451477469 xen/arch/x86/traps.c
--- a/xen/arch/x86/traps.c      Thu Apr 01 09:55:27 2010 +0100
+++ b/xen/arch/x86/traps.c      Sat Apr 03 05:26:53 2010 +0800
@@ -776,7 +776,6 @@ static void pv_cpuid(struct cpu_user_reg
         __clear_bit(X86_FEATURE_PBE, &d);
 
         __clear_bit(X86_FEATURE_DTES64 % 32, &c);
-        __clear_bit(X86_FEATURE_MWAIT % 32, &c);
         __clear_bit(X86_FEATURE_DSCPL % 32, &c);
         __clear_bit(X86_FEATURE_VMXE % 32, &c);
         __clear_bit(X86_FEATURE_SMXE % 32, &c);
@@ -814,7 +813,6 @@ static void pv_cpuid(struct cpu_user_reg
         __clear_bit(X86_FEATURE_SKINIT % 32, &c);
         __clear_bit(X86_FEATURE_WDT % 32, &c);
         break;
-    case 5: /* MONITOR/MWAIT */
     case 0xa: /* Architectural Performance Monitor Features */
     case 0x8000000a: /* SVM revision and features */
     case 0x8000001b: /* Instruction Based Sampling */

Attachment: re-enable-mwait-for-dom0.patch
Description: re-enable-mwait-for-dom0.patch

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