Messages in this thread Patch in this message | | | Date | Thu, 14 Mar 2013 19:23:46 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH] x86/mce: Use MCG_CAP MSR to find out number of banks on AMD |
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On Thu, Mar 14, 2013 at 12:11:18PM -0400, Boris Ostrovsky wrote: > Currently number of error reporting register banks is hardcoded to > 6 on AMD processors. This may break in virtualized scenarios when > a hypervisor prefers to report fewer banks that the physical HW > provides. > > Since number of supported banks is reported in MSR_IA32_MCG_CAP[7:0] > that's what we should use.
Yes, I definitely like it.
A couple of suggestions below :
> > Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> > --- > arch/x86/kernel/cpu/mcheck/mce_amd.c | 21 +++++++++++++-------- > 1 file changed, 13 insertions(+), 8 deletions(-) > > diff --git a/arch/x86/kernel/cpu/mcheck/mce_amd.c b/arch/x86/kernel/cpu/mcheck/mce_amd.c > index 1ac581f..cb7c739 100644 > --- a/arch/x86/kernel/cpu/mcheck/mce_amd.c > +++ b/arch/x86/kernel/cpu/mcheck/mce_amd.c > @@ -33,7 +33,6 @@ > #include <asm/mce.h> > #include <asm/msr.h> > > -#define NR_BANKS 6 > #define NR_BLOCKS 9 > #define THRESHOLD_MAX 0xFFF > #define INT_TYPE_APIC 0x00020000 > @@ -57,9 +56,9 @@ static const char * const th_names[] = { > "execution_unit", > }; > > -static DEFINE_PER_CPU(struct threshold_bank * [NR_BANKS], threshold_banks); > +static DEFINE_PER_CPU(struct threshold_bank **, threshold_banks); > > -static unsigned char shared_bank[NR_BANKS] = { > +static unsigned char shared_bank[MAX_NR_BANKS] = {
This shared_bank thing is a kinda clumsy way of saying that bank 4 is shared. Great, with this change we're allocating a static array of 32 unsigned chars just to ask whether bank 4 is shared. :-)
I know, I know, this was there before but maybe we could clean it up properly while at it.
IOW, we probably want to kill that in a pre-patch and replace the test with:
/* is this a shared bank */ if (bank == 4)
The comment should explain why we're testing this way.
For the future, if we get more shared banks, we could introduce a is_shared_bank() helper but no need to do it just yet.
> 0, 0, 0, 0, 1 > }; > > @@ -214,7 +213,7 @@ void mce_amd_feature_init(struct cpuinfo_x86 *c) > unsigned int bank, block; > int offset = -1; > > - for (bank = 0; bank < NR_BANKS; ++bank) { > + for (bank = 0; bank < mca_cfg.banks; ++bank) { > for (block = 0; block < NR_BLOCKS; ++block) { > if (block == 0) > address = MSR_IA32_MC0_MISC + bank * 4; > @@ -276,7 +275,7 @@ static void amd_threshold_interrupt(void) > mce_setup(&m); > > /* assume first bank caused it */ > - for (bank = 0; bank < NR_BANKS; ++bank) { > + for (bank = 0; bank < mca_cfg.banks; ++bank) { > if (!(per_cpu(bank_map, m.cpu) & (1 << bank))) > continue; > for (block = 0; block < NR_BLOCKS; ++block) { > @@ -467,7 +466,7 @@ static __cpuinit int allocate_threshold_blocks(unsigned int cpu, > u32 low, high; > int err; > > - if ((bank >= NR_BANKS) || (block >= NR_BLOCKS)) > + if ((bank >= mca_cfg.banks) || (block >= NR_BLOCKS)) > return 0; > > if (rdmsr_safe_on_cpu(cpu, address, &low, &high)) > @@ -637,7 +636,12 @@ static __cpuinit int threshold_create_device(unsigned int cpu) > unsigned int bank; > int err = 0; > > - for (bank = 0; bank < NR_BANKS; ++bank) { > + per_cpu(threshold_banks, cpu) = kzalloc(sizeof(struct threshold_bank *) > + * mca_cfg.banks, GFP_KERNEL);
per_cpu accesses are not cheap. You should define a local pointer here and use it instead in all the calls and do the per_cpu assignment only at the end:
per_cpu(threshold_banks, cpu) = local_ptr;
> + if (per_cpu(threshold_banks, cpu) == NULL) > + return -ENOMEM;
Which makes this test much more readable too:
if (!local_ptr) return -ENOMEM;
Btw, those threshold_{create,remove}_device are the hotplug callbacks and the alloc/dealloc looks right but you might want to stress them a bit by taking cores on- and offline while testing, just in case. Thanks.
-- Regards/Gruss, Boris.
Sent from a fat crate under my desk. Formatting is fine. --
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