On Mon, May 23, 2016 at 06:55:06PM -0300, Marcelo Tosatti wrote:
> On Thu, Apr 21, 2016 at 08:21:25PM +0300, Roman Kagan wrote:
> > From: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> >
> > The test checks the relative precision of the reference TSC page
> > and the time reference counter.
> >
> > Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> > [Adjust types to pass printf type checks - Roman Kagan]
> > Signed-off-by: Roman Kagan <rkagan@xxxxxxxxxxxxx>
> > ---
> > x86/Makefile.common | 3 +
> > x86/Makefile.x86_64 | 1 +
> > x86/hyperv.h | 9 +++
> > x86/hyperv_clock.c | 197 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> > x86/unittests.cfg | 5 ++
> > 5 files changed, 215 insertions(+)
> > create mode 100644 x86/hyperv_clock.c
> >
> > diff --git a/x86/Makefile.common b/x86/Makefile.common
> > index ca80367..456e188 100644
> > --- a/x86/Makefile.common
> > +++ b/x86/Makefile.common
> > @@ -123,6 +123,9 @@ $(TEST_DIR)/hyperv_synic.elf: $(cstart.o) $(TEST_DIR)/hyperv.o \
> > $(TEST_DIR)/hyperv_stimer.elf: $(cstart.o) $(TEST_DIR)/hyperv.o \
> > $(TEST_DIR)/hyperv_stimer.o
> >
> > +$(TEST_DIR)/hyperv_clock.elf: $(cstart.o) $(TEST_DIR)/hyperv.o \
> > + $(TEST_DIR)/hyperv_clock.o
> > +
> > $(TEST_DIR)/setjmp.elf: $(cstart.o) $(TEST_DIR)/setjmp.o
> >
> > arch_clean:
> > diff --git a/x86/Makefile.x86_64 b/x86/Makefile.x86_64
> > index 6b7ccfb..56de0f0 100644
> > --- a/x86/Makefile.x86_64
> > +++ b/x86/Makefile.x86_64
> > @@ -14,5 +14,6 @@ tests = $(TEST_DIR)/access.flat $(TEST_DIR)/apic.flat \
> > tests += $(TEST_DIR)/svm.flat
> > tests += $(TEST_DIR)/vmx.flat
> > tests += $(TEST_DIR)/tscdeadline_latency.flat
> > +tests += $(TEST_DIR)/hyperv_clock.flat
> >
> > include $(TEST_DIR)/Makefile.common
> > diff --git a/x86/hyperv.h b/x86/hyperv.h
> > index faf931b..974df56 100644
> > --- a/x86/hyperv.h
> > +++ b/x86/hyperv.h
> > @@ -12,6 +12,7 @@
> > #define HV_X64_MSR_SYNTIMER_AVAILABLE (1 << 3)
> >
> > #define HV_X64_MSR_TIME_REF_COUNT 0x40000020
> > +#define HV_X64_MSR_REFERENCE_TSC 0x40000021
> >
> > /* Define synthetic interrupt controller model specific registers. */
> > #define HV_X64_MSR_SCONTROL 0x40000080
> > @@ -180,4 +181,12 @@ void synic_sint_create(int vcpu, int sint, int vec, bool auto_eoi);
> > void synic_sint_set(int vcpu, int sint);
> > void synic_sint_destroy(int vcpu, int sint);
> >
> > +struct hv_reference_tsc_page {
> > + uint32_t tsc_sequence;
> > + uint32_t res1;
> > + uint64_t tsc_scale;
> > + int64_t tsc_offset;
> > +};
> > +
> > +
> > #endif
> > diff --git a/x86/hyperv_clock.c b/x86/hyperv_clock.c
> > new file mode 100644
> > index 0000000..a346d99
> > --- /dev/null
> > +++ b/x86/hyperv_clock.c
> > @@ -0,0 +1,197 @@
> > +#include "libcflat.h"
> > +#include "smp.h"
> > +#include "atomic.h"
> > +#include "processor.h"
> > +#include "hyperv.h"
> > +#include "vm.h"
> > +
> > +#define MAX_CPU 4
> > +#define TICKS_PER_SEC (1000000000 / 100)
> > +
> > +struct hv_reference_tsc_page *tsc_ref;
> > +
> > +/*
> > + * Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction,
> > + * yielding a 64-bit result.
> > + */
> > +static inline u64 scale_delta(u64 delta, u64 mul_frac)
> > +{
> > + u64 product, unused;
> > +
> > + __asm__ (
> > + "mul %3"
> > + : "=d" (product), "=a" (unused) : "1" (delta), "rm" ((u64)mul_frac) );
> > +
> > + return product;
> > +}
> > +
> > +static u64 hvclock_tsc_to_ticks(struct hv_reference_tsc_page *shadow, u64 tsc)
> > +{
> > + return scale_delta(tsc, shadow->tsc_scale) + shadow->tsc_offset;
> > +}
> > +
> > +/*
> > + * Reads a consistent set of time-base values from hypervisor,
> > + * into a shadow data area.
> > + */
> > +static void hvclock_get_time_values(struct hv_reference_tsc_page *shadow,
> > + struct hv_reference_tsc_page *page)
> > +{
> > + int seq;
> > + do {
> > + seq = page->tsc_sequence;
> > + rmb(); /* fetch version before data */
> > + *shadow = *page;
> > + rmb(); /* test version after fetching data */
> > + } while (shadow->tsc_sequence != seq);
> > +}
> > +
> > +u64 tsc_ref_read(void)
> > +{
> > + struct hv_reference_tsc_page shadow;
> > +
> > + hvclock_get_time_values(&shadow, tsc_ref);
> > + return hvclock_tsc_to_ticks(&shadow, rdtsc());
> > +}
> > +
> > +atomic_t cpus_left;
> > +bool ok[MAX_CPU];
> > +u64 loops[MAX_CPU];
> > +
> > +static void tsc_ref_test(void *data)
> > +{
> > + int i = smp_id();
> > + unsigned long long t = rdmsr(HV_X64_MSR_TIME_REF_COUNT);
> > + unsigned long long end = t + 3 * TICKS_PER_SEC;
> > +
> > + ok[i] = true;
> > + do {
> > + u64 now = tsc_ref_read();
> > + if (now < t) {
> > + printf("warp on CPU %d!\n", smp_id());
> > + ok[i] = false;
> > + break;
> > + }
> > + t = now;
> > + } while(t < end);
> > +
> > + barrier();
>
> ***
>
>
> > + if (t >= end) {
> > + long long ref = rdmsr(HV_X64_MSR_TIME_REF_COUNT);
> > + if (i == 0)
> > + printf("Time reference MSR drift: %lld\n\n", ref - end);
> > + ok[i] &= (ref - end) > -5 && (ref - end) < 5;
>
> This is prone to fail: guest can be scheduled at "***" above and
> test will fail.
>
> The [-5,5] comes from the standard? What the standard dictates?
I suppose this would be a better test
do {
u64 now_refpage; tsc_ref_read();
u64 now_refcount;
now_refpage = tsc_ref_read();
now_refcount = rdmsr(HV_X64_MSR_TIME_REF_COUNT);
if (now_refpage > now_refcount) {
printf("now_refpage %ld > now_refcount %ld\n",
now_refpage, now_refcount);
}
which fails once you run
void main(void)
{
int ret;
struct timex tx;
char *ptr;
memset((void*)&tx, 0, sizeof(tx));
tx.freq = -6553600;
//tx.freq = -237507;
tx.modes = ADJ_FREQUENCY;
ret = adjtimex(&tx);
(such failure would crash applications with time backwards).
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