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Subject[tip:x86/urgent] x86: mce: Use safer ways to access MCE registers
Commit-ID:  11868a2dc4f5e4f2f652bfd259e1360193fcee62
Gitweb: http://git.kernel.org/tip/11868a2dc4f5e4f2f652bfd259e1360193fcee62
Author: Ingo Molnar <mingo@elte.hu>
AuthorDate: Wed, 23 Sep 2009 17:49:55 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Wed, 23 Sep 2009 18:08:26 +0200

x86: mce: Use safer ways to access MCE registers

Use rdmsrl_safe() when accessing MCE registers. While in
theory we always 'know' which ones are safe to access from
the capability bits, there's a lot of hardware variations
and reality might differ from theory, as it did in this case:

http://bugzilla.kernel.org/show_bug.cgi?id=14204

[ 0.010016] mce: CPU supports 5 MCE banks
[ 0.011029] general protection fault: 0000 [#1]
[ 0.011998] last sysfs file:
[ 0.011998] Modules linked in:
[ 0.011998]
[ 0.011998] Pid: 0, comm: swapper Not tainted (2.6.31_router #1) HP Vectra
[ 0.011998] EIP: 0060:[<c100d9b9>] EFLAGS: 00010246 CPU: 0
[ 0.011998] EIP is at mce_rdmsrl+0x19/0x60
[ 0.011998] EAX: 00000000 EBX: 00000001 ECX: 00000407 EDX: 08000000
[ 0.011998] ESI: 00000000 EDI: 8c000000 EBP: 00000405 ESP: c17d5eac

So WARN_ONCE() instead of crashing the box.

( also fix a number of stylistic inconsistencies in the code. )

Note, we might still crash in wrmsrl() if we get that far, but
we shouldnt if the registers are truly inaccessible.

Reported-by: GNUtoo <GNUtoo@no-log.org>
Cc: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
LKML-Reference: <bug-14204-5438@http.bugzilla.kernel.org/>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
arch/x86/kernel/cpu/mcheck/mce.c | 23 +++++++++++++++++++++--
1 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 2f5aab2..4b2af86 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -305,13 +305,25 @@ static int msr_to_offset(u32 msr)
static u64 mce_rdmsrl(u32 msr)
{
u64 v;
+
if (__get_cpu_var(injectm).finished) {
int offset = msr_to_offset(msr);
+
if (offset < 0)
return 0;
return *(u64 *)((char *)&__get_cpu_var(injectm) + offset);
}
- rdmsrl(msr, v);
+
+ if (rdmsrl_safe(msr, &v)) {
+ WARN_ONCE(1, "mce: Unable to read msr %d!\n", msr);
+ /*
+ * Return zero in case the access faulted. This should
+ * not happen normally but can happen if the CPU does
+ * something weird, or if the code is buggy.
+ */
+ v = 0;
+ }
+
return v;
}

@@ -319,6 +331,7 @@ static void mce_wrmsrl(u32 msr, u64 v)
{
if (__get_cpu_var(injectm).finished) {
int offset = msr_to_offset(msr);
+
if (offset >= 0)
*(u64 *)((char *)&__get_cpu_var(injectm) + offset) = v;
return;
@@ -415,7 +428,7 @@ static inline void mce_get_rip(struct mce *m, struct pt_regs *regs)
m->ip = mce_rdmsrl(rip_msr);
}

-#ifdef CONFIG_X86_LOCAL_APIC
+#ifdef CONFIG_X86_LOCAL_APIC
/*
* Called after interrupts have been reenabled again
* when a MCE happened during an interrupts off region
@@ -1172,6 +1185,7 @@ static int mce_banks_init(void)
return -ENOMEM;
for (i = 0; i < banks; i++) {
struct mce_bank *b = &mce_banks[i];
+
b->ctl = -1ULL;
b->init = 1;
}
@@ -1203,6 +1217,7 @@ static int __cpuinit mce_cap_init(void)
banks = b;
if (!mce_banks) {
int err = mce_banks_init();
+
if (err)
return err;
}
@@ -1237,6 +1252,7 @@ static void mce_init(void)

for (i = 0; i < banks; i++) {
struct mce_bank *b = &mce_banks[i];
+
if (!b->init)
continue;
wrmsrl(MSR_IA32_MCx_CTL(i), b->ctl);
@@ -1626,6 +1642,7 @@ static int mce_disable(void)

for (i = 0; i < banks; i++) {
struct mce_bank *b = &mce_banks[i];
+
if (b->init)
wrmsrl(MSR_IA32_MCx_CTL(i), 0);
}
@@ -1911,6 +1928,7 @@ static void mce_disable_cpu(void *h)
cmci_clear();
for (i = 0; i < banks; i++) {
struct mce_bank *b = &mce_banks[i];
+
if (b->init)
wrmsrl(MSR_IA32_MCx_CTL(i), 0);
}
@@ -1928,6 +1946,7 @@ static void mce_reenable_cpu(void *h)
cmci_reenable();
for (i = 0; i < banks; i++) {
struct mce_bank *b = &mce_banks[i];
+
if (b->init)
wrmsrl(MSR_IA32_MCx_CTL(i), b->ctl);
}

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