[Xen-devel] [PATCH] x86/AMD: Do not enable ARAT feature on AMD processors below family 0x12

[Boris Ostrovsky <boris.ostrovsky@xxxxxxx>]

# HG changeset patch
# User Boris Ostrovsky <boris.ostrovsky@xxxxxxx>
# Date 1317915395 14400
# Node ID 4374a261682e78d6bbf3b3fefb1e779b7a1fc3b3
# Parent  0b66e6450ffe6823d8b323ef4248b38fe7372d54
x86/AMD: Do not enable ARAT feature on AMD processors below family 0x12

Determining whether an AMD processor is affected by erratum 400 may
have some corner cases and handling these cases is somewhat complicated.
In the interest of simplicity we won't claim ARAT support on processor
families below 0x12.

Mirrors Linux commit e9cdd343a5e42c43bcda01e609fa23089e026470

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxx>

diff -r 0b66e6450ffe -r 4374a261682e xen/arch/x86/cpu/amd.c
--- a/xen/arch/x86/cpu/amd.c    Tue Oct 04 14:18:30 2011 +0200
+++ b/xen/arch/x86/cpu/amd.c    Thu Oct 06 11:36:35 2011 -0400
@@ -495,8 +495,11 @@
        }
 #endif
 
-       /* As a rule processors have APIC timer running in deep C states */
-       if (c->x86 > 0xf && !cpu_has_amd_erratum(c, AMD_ERRATUM_400))
+       /*
+        * Family 0x12 and above processors have APIC timer
+        * running in deep C states.
+        */
+       if (c->x86 > 0x11)
                set_bit(X86_FEATURE_ARAT, c->x86_capability);
 
        if (cpuid_edx(0x80000007) & (1 << 10)) {


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