[Xen-devel] [PATCH] x86, AMD: Fix crash as Xen Dom0 on AMD Trinity systems

[Borislav Petkov <bp@xxxxxxxxx>]

From: Andre Przywara <andre.przywara@xxxxxxx>

f7f286a910221 ("x86/amd: Re-enable CPU topology extensions in case BIOS
has disabled it") wrongfully added code which used the AMD-specific
{rd,wr}msr variants for no real reason.

This caused boot panics on xen which wasn't initializing the
{rd,wr}msr_safe_regs pv_ops members properly.

This, in turn, caused a heated discussion leading to us reviewing all
uses of the AMD-specific variants and removing them where unneeded
(almost everywhere except an obscure K8 BIOS fix, see 6b0f43ddfa358).

Finally, this patch switches to the standard {rd,wr}msr*_safe* variants
which should've been used in the first place anyway and avoided unneeded
excitation with xen.

Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
Cc: Andreas Herrmann <andreas.herrmann3@xxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # 3.4+
Link: 
<http://lkml.kernel.org/r/1338383402-3838-1-git-send-email-andre.przywara@xxxxxxx>
[Boris: correct and expand commit message]
Signed-off-by: Borislav Petkov <borislav.petkov@xxxxxxx>
---
 arch/x86/kernel/cpu/amd.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 146bb6218eec..80ccd99542e6 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -586,9 +586,9 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c)
            !cpu_has(c, X86_FEATURE_TOPOEXT)) {
                u64 val;
 
-               if (!rdmsrl_amd_safe(0xc0011005, &val)) {
+               if (!rdmsrl_safe(0xc0011005, &val)) {
                        val |= 1ULL << 54;
-                       wrmsrl_amd_safe(0xc0011005, val);
+                       checking_wrmsrl(0xc0011005, val);
                        rdmsrl(0xc0011005, val);
                        if (val & (1ULL << 54)) {
                                set_cpu_cap(c, X86_FEATURE_TOPOEXT);
-- 
1.7.9.3.362.g71319


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