Re: [PATCH] Intel/VPMU: Add support for full-width PMC writes

[Boris Ostrovsky <boris.ostrovsky@oracle.com>]

On 07/29/2013 05:56 AM, Dietmar Hahn wrote:
> Am Montag 22 Juli 2013, 14:54:31 schrieb Boris Ostrovsky:
>> A recent Linux commit (069e0c3c405814778c7475d95b9fff5318f39834) added
>> support for full-width PMC writes to performance counter registers,
>> making these registers default for perf. Since current Xen VPMU does
>> not support these new MSRs perf will fail to initialise in guests.
>>
>> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
>>
>> Question to Intel folks: Do we need to update MSR bitmap for both original
>> (0xc1) and alias (0x4c1) registers or will either one suffice?

Ping to Intel engineers.

I'll resend this with fixes but I'd like to hear first whether I really 
need to deal
with MSR bitmaps. I could test to see how it behaves on my system but I am
not convinced that even if bitmap uses single bit for both aliases on my 
HW it
will be safe to assume that this is the expected behavior on all processors.

Thanks
-boris


>>
>> ---
>>   xen/arch/x86/hvm/vmx/vpmu_core2.c | 44 +++++++++++++++++++++++++++++++++++----
>>   xen/include/asm-x86/msr-index.h   |  1 +
>>   2 files changed, 41 insertions(+), 4 deletions(-)
>>
>> diff --git a/xen/arch/x86/hvm/vmx/vpmu_core2.c b/xen/arch/x86/hvm/vmx/vpmu_core2.c
>> index 15b2036..823d364 100644
>> --- a/xen/arch/x86/hvm/vmx/vpmu_core2.c
>> +++ b/xen/arch/x86/hvm/vmx/vpmu_core2.c
>> @@ -64,6 +64,10 @@
>>   #define PMU_FIXED_WIDTH_BITS     8  /* 8 bits 5..12 */
>>   #define PMU_FIXED_WIDTH_MASK     (((1 << PMU_FIXED_WIDTH_BITS) -1) << PMU_FIXED_WIDTH_SHIFT)
>>   
>> +/* Alias registers (0x4c1) for full-width writes to PMCs */
>> +#define MSR_PMC_ALIAS_MASK       (~0x400)
>> +bool_t __read_mostly fw_write;
> Why not use "full_width_write" (or similar) like in the original linux kernel
> patch for better readability?
>
>> +
>>   /*
>>    * QUIRK to workaround an issue on various family 6 cpus.
>>    * The issue leads to endless PMC interrupt loops on the processor.
>> @@ -195,6 +199,7 @@ static int core2_get_bitwidth_fix_count(void)
>>   static int is_core2_vpmu_msr(u32 msr_index, int *type, int *index)
>>   {
>>       int i;
>> +    u32 msr_index_pmc;
>>   
>>       for ( i = 0; i < core2_fix_counters.num; i++ )
>>       {
>> @@ -224,11 +229,12 @@ static int is_core2_vpmu_msr(u32 msr_index, int *type, int *index)
>>           return 1;
>>       }
>>   
>> -    if ( (msr_index >= MSR_IA32_PERFCTR0) &&
>> -         (msr_index < (MSR_IA32_PERFCTR0 + core2_get_pmc_count())) )
>> +    msr_index_pmc =  msr_index & MSR_PMC_ALIAS_MASK;
>> +    if ( (msr_index_pmc >= MSR_IA32_PERFCTR0) &&
>> +         (msr_index_pmc < (MSR_IA32_PERFCTR0 + core2_get_pmc_count())) )
>>       {
>>           *type = MSR_TYPE_ARCH_COUNTER;
>> -        *index = msr_index - MSR_IA32_PERFCTR0;
>> +        *index = msr_index_pmc - MSR_IA32_PERFCTR0;
>>           return 1;
>>       }
>>   
>> @@ -260,6 +266,15 @@ static void core2_vpmu_set_msr_bitmap(unsigned long *msr_bitmap)
>>           clear_bit(msraddr_to_bitpos(MSR_IA32_PERFCTR0+i),
>>                     msr_bitmap + 0x800/BYTES_PER_LONG);
>>       }
>> +    if ( fw_write )
>> +    {
>> +        for ( i = 0; i < core2_get_pmc_count(); i++ )
>> +        {
>> +            clear_bit(msraddr_to_bitpos(MSR_IA32_A_PERFCTR0+i), msr_bitmap);
>> +            clear_bit(msraddr_to_bitpos(MSR_IA32_A_PERFCTR0+i),
>> +                      msr_bitmap + 0x800/BYTES_PER_LONG);
>> +        }
>> +    }
>>   
>>       /* Allow Read PMU Non-global Controls Directly. */
>>       for ( i = 0; i < core2_ctrls.num; i++ )
>> @@ -284,6 +299,16 @@ static void core2_vpmu_unset_msr_bitmap(unsigned long *msr_bitmap)
>>           set_bit(msraddr_to_bitpos(MSR_IA32_PERFCTR0+i),
>>                   msr_bitmap + 0x800/BYTES_PER_LONG);
>>       }
>> +    if ( fw_write )
>> +    {
>> +        for ( i = 0; i < core2_get_pmc_count(); i++ )
>> +        {
>> +            set_bit(msraddr_to_bitpos(MSR_IA32_A_PERFCTR0+i), msr_bitmap);
>> +            set_bit(msraddr_to_bitpos(MSR_IA32_A_PERFCTR0+i),
>> +                      msr_bitmap + 0x800/BYTES_PER_LONG);
>> +        }
>> +    }
>> +
>>       for ( i = 0; i < core2_ctrls.num; i++ )
>>           set_bit(msraddr_to_bitpos(core2_ctrls.msr[i]), msr_bitmap);
>>       for ( i = 0; i < core2_get_pmc_count(); i++ )
>> @@ -324,11 +349,17 @@ static inline void __core2_vpmu_load(struct vcpu *v)
>>   {
>>       int i;
>>       struct core2_vpmu_context *core2_vpmu_cxt = vcpu_vpmu(v)->context;
>> +    int pmc_start;
>>   
>>       for ( i = 0; i < core2_fix_counters.num; i++ )
>>           wrmsrl(core2_fix_counters.msr[i], core2_vpmu_cxt->fix_counters[i]);
>> +
> Leading spaces.
>
> Reviewed-by: Dietmar Hahn <dietmar.hahn@ts.fujitsu.com>
>
>
>> +    if ( fw_write )
>> +        pmc_start = MSR_IA32_A_PERFCTR0;
>> +    else
>> +        pmc_start = MSR_IA32_PERFCTR0;
>>       for ( i = 0; i < core2_get_pmc_count(); i++ )
>> -        wrmsrl(MSR_IA32_PERFCTR0+i, core2_vpmu_cxt->arch_msr_pair[i].counter);
>> +        wrmsrl(pmc_start+i, core2_vpmu_cxt->arch_msr_pair[i].counter);
>>   
>>       for ( i = 0; i < core2_ctrls.num; i++ )
>>           wrmsrl(core2_ctrls.msr[i], core2_vpmu_cxt->ctrls[i]);
>> @@ -855,6 +886,11 @@ int vmx_vpmu_initialise(struct vcpu *v, unsigned int vpmu_flags)
>>   
>>       if ( family == 6 )
>>       {
>> +        u64 caps;
>> +
>> +        rdmsrl(MSR_IA32_PERF_CAPABILITIES, caps);
>> +        fw_write = (caps >> 13) & 1;
>> +
>>           switch ( cpu_model )
>>           {
>>           /* Core2: */
>> diff --git a/xen/include/asm-x86/msr-index.h b/xen/include/asm-x86/msr-index.h
>> index f500efd..5acaee8 100644
>> --- a/xen/include/asm-x86/msr-index.h
>> +++ b/xen/include/asm-x86/msr-index.h
>> @@ -34,6 +34,7 @@
>>   /* Intel MSRs. Some also available on other CPUs */
>>   #define MSR_IA32_PERFCTR0		0x000000c1
>>   #define MSR_IA32_PERFCTR1		0x000000c2
>> +#define MSR_IA32_A_PERFCTR0		0x000004c1
>>   #define MSR_FSB_FREQ			0x000000cd
>>   
>>   #define MSR_NHM_SNB_PKG_CST_CFG_CTL	0x000000e2
>>