Re: [PATCH kvm-unit-tests v2] pmu: fixes for Sandy Bridge hosts

[Gleb Natapov <gleb@redhat.com>]

On Mon, Jun 03, 2013 at 08:35:21AM +0200, Paolo Bonzini wrote:
> Il 02/06/2013 17:33, Gleb Natapov ha scritto:
> > On Thu, May 30, 2013 at 07:47:18PM +0200, Paolo Bonzini wrote:
> >> This patch includes two fixes for SB:
> >>
> >> * the 3rd fixed counter ("ref cpu cycles") can sometimes report
> >>   less than the number of iterations
> >>
> >> * there is an 8th counter which causes out of bounds accesses
> >>   to gp_event or check_counters_many's cnt array
> >>
> >> There is still a bug in KVM, because the "pmu all counters-0"
> >> test fails.  (It passes if you use any 6 of the 8 gp counters,
> >> fails if you use 7 or 8).
> >>
> > Changelog?
> 
> Changelog is simply that the patch applies. :(
> 
Just say so, I tried to see how they are different and failed.

> v1 was hand-edited and I did not regenerate it after testing the edit:
> 
> -@@ -395,6 +396,14 @@ int main(int ac, char **av)
> +@@ -395,6 +396,10 @@ int main(int ac, char **av)
> 
Yeah, hard to spot :)

> Paolo
> 
> >> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> >> ---
> >>  x86/pmu.c | 21 +++++++++++++++------
> >>  1 file changed, 15 insertions(+), 6 deletions(-)
> >>
> >> diff --git a/x86/pmu.c b/x86/pmu.c
> >> index 2c46f31..dca753a 100644
> >> --- a/x86/pmu.c
> >> +++ b/x86/pmu.c
> >> @@ -88,9 +88,10 @@ struct pmu_event {
> >>  }, fixed_events[] = {
> >>  	{"fixed 1", MSR_CORE_PERF_FIXED_CTR0, 10*N, 10.2*N},
> >>  	{"fixed 2", MSR_CORE_PERF_FIXED_CTR0 + 1, 1*N, 30*N},
> >> -	{"fixed 3", MSR_CORE_PERF_FIXED_CTR0 + 2, 1*N, 30*N}
> >> +	{"fixed 3", MSR_CORE_PERF_FIXED_CTR0 + 2, 0.1*N, 30*N}
> >>  };
> >>  
> >> +static int num_counters;
> >>  static int tests, failures;
> >>  
> >>  char *buf;
> >> @@ -237,7 +238,7 @@ static void check_gp_counter(struct pmu_event *evt)
> >>  	};
> >>  	int i;
> >>  
> >> -	for (i = 0; i < eax.split.num_counters; i++, cnt.ctr++) {
> >> +	for (i = 0; i < num_counters; i++, cnt.ctr++) {
> >>  		cnt.count = 0;
> >>  		measure(&cnt, 1);
> >>  		report(evt->name, i, verify_event(cnt.count, evt));
> >> @@ -276,7 +277,7 @@ static void check_counters_many(void)
> >>  	pmu_counter_t cnt[10];
> >>  	int i, n;
> >>  
> >> -	for (i = 0, n = 0; n < eax.split.num_counters; i++) {
> >> +	for (i = 0, n = 0; n < num_counters; i++) {
> >>  		if (ebx.full & (1 << i))
> >>  			continue;
> >>  
> >> @@ -316,10 +317,10 @@ static void check_counter_overflow(void)
> >>  	/* clear status before test */
> >>  	wrmsr(MSR_CORE_PERF_GLOBAL_OVF_CTRL, rdmsr(MSR_CORE_PERF_GLOBAL_STATUS));
> >>  
> >> -	for (i = 0; i < eax.split.num_counters + 1; i++, cnt.ctr++) {
> >> +	for (i = 0; i < num_counters + 1; i++, cnt.ctr++) {
> >>  		uint64_t status;
> >>  		int idx;
> >> -		if (i == eax.split.num_counters)
> >> +		if (i == num_counters)
> >>  			cnt.ctr = fixed_events[0].unit_sel;
> >>  		if (i % 2)
> >>  			cnt.config |= EVNTSEL_INT;
> >> @@ -355,7 +356,7 @@ static void check_rdpmc(void)
> >>  	uint64_t val = 0x1f3456789ull;
> >>  	int i;
> >>  
> >> -	for (i = 0; i < eax.split.num_counters; i++) {
> >> +	for (i = 0; i < num_counters; i++) {
> >>  		uint64_t x = (val & 0xffffffff) |
> >>  			((1ull << (eax.split.bit_width - 32)) - 1) << 32;
> >>  		wrmsr(MSR_IA32_PERFCTR0 + i, val);
> >> @@ -395,6 +396,10 @@ int main(int ac, char **av)
> >>  	printf("Fixed counters:      %d\n", edx.split.num_counters_fixed);
> >>  	printf("Fixed counter width: %d\n", edx.split.bit_width_fixed);
> >>  
> >> +	num_counters = eax.split.num_counters;
> >> +	if (num_counters > ARRAY_SIZE(gp_events))
> >> +		num_counters = ARRAY_SIZE(gp_events);
> >> +
> >>  	apic_write(APIC_LVTPC, PC_VECTOR);
> >>  
> >>  	check_gp_counters();
> >> -- 
> >> 1.8.2.1
> >>
> >> --
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> > 
> > --
> > 			Gleb.
> > --
> > To unsubscribe from this list: send the line "unsubscribe kvm" in
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> > 

--
			Gleb.