[PATCH x86 for review II] [17/39] x86_64: Tighten mce_amd driver MSR reads

Andi Kleen
2007-02-12T07:40:19Z

From: "Jan Beulich" <jbeulich@novell.com>

while debugging an unrelated problem in Xen, I noticed odd reads from
non-existent MSRs. Having now found time to look why these happen, I
came up with below patch, which
- prevents accessing MCi_MISCj with j > 0 when the block pointer in
MCi_MISC0 is zero
- accesses only contiguous MCi_MISCj until a non-implemented one is
found
- doesn't touch unimplemented blocks in mce_threshold_interrupt at all
- gives names to two bits previously derived from MASK_VALID_HI (it
took me some time to understand the code without this)

The first three items, besides being apparently closer to the spec, should
namely help cutting down on the time mce_threshold_interrupt() takes.

Signed-off-by: Andi Kleen <ak@suse.de>

---
arch/x86_64/kernel/mce_amd.c | 40 +++++++++++++++++++++++++---------------
1 file changed, 25 insertions(+), 15 deletions(-)

Index: linux/arch/x86_64/kernel/mce_amd.c
===================================================================
--- linux.orig/arch/x86_64/kernel/mce_amd.c
+++ linux/arch/x86_64/kernel/mce_amd.c
@@ -37,6 +37,8 @@
#define THRESHOLD_MAX 0xFFF
#define INT_TYPE_APIC 0x00020000
#define MASK_VALID_HI 0x80000000
+#define MASK_CNTP_HI 0x40000000
+#define MASK_LOCKED_HI 0x20000000
#define MASK_LVTOFF_HI 0x00F00000
#define MASK_COUNT_EN_HI 0x00080000
#define MASK_INT_TYPE_HI 0x00060000
@@ -122,14 +124,17 @@ void __cpuinit mce_amd_feature_init(stru
for (block = 0; block < NR_BLOCKS; ++block) {
if (block == 0)
address = MSR_IA32_MC0_MISC + bank * 4;
- else if (block == 1)
- address = MCG_XBLK_ADDR
- + ((low & MASK_BLKPTR_LO) >> 21);
+ else if (block == 1) {
+ address = (low & MASK_BLKPTR_LO) >> 21;
+ if (!address)
+ break;
+ address += MCG_XBLK_ADDR;
+ }
else
++address;

if (rdmsr_safe(address, &low, &high))
- continue;
+ break;

if (!(high & MASK_VALID_HI)) {
if (block)
@@ -138,8 +143,8 @@ void __cpuinit mce_amd_feature_init(stru
break;
}

- if (!(high & MASK_VALID_HI >> 1) ||
- (high & MASK_VALID_HI >> 2))
+ if (!(high & MASK_CNTP_HI) ||
+ (high & MASK_LOCKED_HI))
continue;

if (!block)
@@ -187,17 +192,22 @@ asmlinkage void mce_threshold_interrupt(

/* assume first bank caused it */
for (bank = 0; bank < NR_BANKS; ++bank) {
+ if (!(per_cpu(bank_map, m.cpu) & (1 << bank)))
+ continue;
for (block = 0; block < NR_BLOCKS; ++block) {
if (block == 0)
address = MSR_IA32_MC0_MISC + bank * 4;
- else if (block == 1)
- address = MCG_XBLK_ADDR
- + ((low & MASK_BLKPTR_LO) >> 21);
+ else if (block == 1) {
+ address = (low & MASK_BLKPTR_LO) >> 21;
+ if (!address)
+ break;
+ address += MCG_XBLK_ADDR;
+ }
else
++address;

if (rdmsr_safe(address, &low, &high))
- continue;
+ break;

if (!(high & MASK_VALID_HI)) {
if (block)
@@ -206,8 +216,8 @@ asmlinkage void mce_threshold_interrupt(
break;
}

- if (!(high & MASK_VALID_HI >> 1) ||
- (high & MASK_VALID_HI >> 2))
+ if (!(high & MASK_CNTP_HI) ||
+ (high & MASK_LOCKED_HI))
continue;

if (high & MASK_OVERFLOW_HI) {
@@ -385,7 +395,7 @@ static __cpuinit int allocate_threshold_
return 0;

if (rdmsr_safe(address, &low, &high))
- goto recurse;
+ return 0;

if (!(high & MASK_VALID_HI)) {
if (block)
@@ -394,8 +404,8 @@ static __cpuinit int allocate_threshold_
return 0;
}

- if (!(high & MASK_VALID_HI >> 1) ||
- (high & MASK_VALID_HI >> 2))
+ if (!(high & MASK_CNTP_HI) ||
+ (high & MASK_LOCKED_HI))
goto recurse;

b = kzalloc(sizeof(struct threshold_block), GFP_KERNEL);