Skip to content

Commit

Permalink
selftests: kvm: Add basic Hyper-V clocksources tests
Browse files Browse the repository at this point in the history 
Introduce a new selftest for Hyper-V clocksources (MSR-based reference TSC
and TSC page). As a starting point, test the following:
1) Reference TSC is 1Ghz clock.
2) Reference TSC and TSC page give the same reading.
3) TSC page gets updated upon KVM_SET_CLOCK call.
4) TSC page does not get updated when guest opted for reenlightenment.
5) Disabled TSC page doesn't get updated.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210318140949.1065740-1-vkuznets@redhat.com>
[Add a host-side test using TSC + KVM_GET_MSR too. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
  • Loading branch information
Vitaly Kuznetsov authored and Paolo Bonzini committed Mar 18, 2021
1 parent 0469f2f commit 2c7f76b
Show file tree
Hide file tree
Showing 3 changed files with 262 additions and 0 deletions.
1 change: 1 addition & 0 deletions tools/testing/selftests/kvm/.gitignore
View file
Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@
/x86_64/evmcs_test
/x86_64/get_cpuid_test
/x86_64/kvm_pv_test
/x86_64/hyperv_clock
/x86_64/hyperv_cpuid
/x86_64/mmio_warning_test
/x86_64/platform_info_test
Expand Down
1 change: 1 addition & 0 deletions tools/testing/selftests/kvm/Makefile
View file
Original file line number Diff line number Diff line change
Expand Up @@ -41,6 +41,7 @@ LIBKVM_s390x = lib/s390x/processor.c lib/s390x/ucall.c lib/s390x/diag318_test_ha
TEST_GEN_PROGS_x86_64 = x86_64/cr4_cpuid_sync_test
TEST_GEN_PROGS_x86_64 += x86_64/evmcs_test
TEST_GEN_PROGS_x86_64 += x86_64/get_cpuid_test
TEST_GEN_PROGS_x86_64 += x86_64/hyperv_clock
TEST_GEN_PROGS_x86_64 += x86_64/hyperv_cpuid
TEST_GEN_PROGS_x86_64 += x86_64/kvm_pv_test
TEST_GEN_PROGS_x86_64 += x86_64/mmio_warning_test
Expand Down
260 changes: 260 additions & 0 deletions tools/testing/selftests/kvm/x86_64/hyperv_clock.c
View file
Original file line number Diff line number Diff line change
@@ -0,0 +1,260 @@
// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2021, Red Hat, Inc.
*
* Tests for Hyper-V clocksources
*/
#include "test_util.h"
#include "kvm_util.h"
#include "processor.h"

struct ms_hyperv_tsc_page {
volatile u32 tsc_sequence;
u32 reserved1;
volatile u64 tsc_scale;
volatile s64 tsc_offset;
} __packed;

#define HV_X64_MSR_GUEST_OS_ID 0x40000000
#define HV_X64_MSR_TIME_REF_COUNT 0x40000020
#define HV_X64_MSR_REFERENCE_TSC 0x40000021
#define HV_X64_MSR_TSC_FREQUENCY 0x40000022
#define HV_X64_MSR_REENLIGHTENMENT_CONTROL 0x40000106
#define HV_X64_MSR_TSC_EMULATION_CONTROL 0x40000107

/* Simplified mul_u64_u64_shr() */
static inline u64 mul_u64_u64_shr64(u64 a, u64 b)
{
union {
u64 ll;
struct {
u32 low, high;
} l;
} rm, rn, rh, a0, b0;
u64 c;

a0.ll = a;
b0.ll = b;

rm.ll = (u64)a0.l.low * b0.l.high;
rn.ll = (u64)a0.l.high * b0.l.low;
rh.ll = (u64)a0.l.high * b0.l.high;

rh.l.low = c = rm.l.high + rn.l.high + rh.l.low;
rh.l.high = (c >> 32) + rh.l.high;

return rh.ll;
}

static inline void nop_loop(void)
{
int i;

for (i = 0; i < 1000000; i++)
asm volatile("nop");
}

static inline void check_tsc_msr_rdtsc(void)
{
u64 tsc_freq, r1, r2, t1, t2;
s64 delta_ns;

tsc_freq = rdmsr(HV_X64_MSR_TSC_FREQUENCY);
GUEST_ASSERT(tsc_freq > 0);

/* First, check MSR-based clocksource */
r1 = rdtsc();
t1 = rdmsr(HV_X64_MSR_TIME_REF_COUNT);
nop_loop();
r2 = rdtsc();
t2 = rdmsr(HV_X64_MSR_TIME_REF_COUNT);

GUEST_ASSERT(r2 > r1 && t2 > t1);

/* HV_X64_MSR_TIME_REF_COUNT is in 100ns */
delta_ns = ((t2 - t1) * 100) - ((r2 - r1) * 1000000000 / tsc_freq);
if (delta_ns < 0)
delta_ns = -delta_ns;

/* 1% tolerance */
GUEST_ASSERT(delta_ns * 100 < (t2 - t1) * 100);
}

static inline void check_tsc_msr_tsc_page(struct ms_hyperv_tsc_page *tsc_page)
{
u64 r1, r2, t1, t2;

/* Compare TSC page clocksource with HV_X64_MSR_TIME_REF_COUNT */
t1 = mul_u64_u64_shr64(rdtsc(), tsc_page->tsc_scale) + tsc_page->tsc_offset;
r1 = rdmsr(HV_X64_MSR_TIME_REF_COUNT);

/* 10 ms tolerance */
GUEST_ASSERT(r1 >= t1 && r1 - t1 < 100000);
nop_loop();

t2 = mul_u64_u64_shr64(rdtsc(), tsc_page->tsc_scale) + tsc_page->tsc_offset;
r2 = rdmsr(HV_X64_MSR_TIME_REF_COUNT);
GUEST_ASSERT(r2 >= t1 && r2 - t2 < 100000);
}

static void guest_main(struct ms_hyperv_tsc_page *tsc_page, vm_paddr_t tsc_page_gpa)
{
u64 tsc_scale, tsc_offset;

/* Set Guest OS id to enable Hyper-V emulation */
GUEST_SYNC(1);
wrmsr(HV_X64_MSR_GUEST_OS_ID, (u64)0x8100 << 48);
GUEST_SYNC(2);

check_tsc_msr_rdtsc();

GUEST_SYNC(3);

/* Set up TSC page is disabled state, check that it's clean */
wrmsr(HV_X64_MSR_REFERENCE_TSC, tsc_page_gpa);
GUEST_ASSERT(tsc_page->tsc_sequence == 0);
GUEST_ASSERT(tsc_page->tsc_scale == 0);
GUEST_ASSERT(tsc_page->tsc_offset == 0);

GUEST_SYNC(4);

/* Set up TSC page is enabled state */
wrmsr(HV_X64_MSR_REFERENCE_TSC, tsc_page_gpa | 0x1);
GUEST_ASSERT(tsc_page->tsc_sequence != 0);

GUEST_SYNC(5);

check_tsc_msr_tsc_page(tsc_page);

GUEST_SYNC(6);

tsc_offset = tsc_page->tsc_offset;
/* Call KVM_SET_CLOCK from userspace, check that TSC page was updated */
GUEST_SYNC(7);
GUEST_ASSERT(tsc_page->tsc_offset != tsc_offset);

nop_loop();

/*
* Enable Re-enlightenment and check that TSC page stays constant across
* KVM_SET_CLOCK.
*/
wrmsr(HV_X64_MSR_REENLIGHTENMENT_CONTROL, 0x1 << 16 | 0xff);
wrmsr(HV_X64_MSR_TSC_EMULATION_CONTROL, 0x1);
tsc_offset = tsc_page->tsc_offset;
tsc_scale = tsc_page->tsc_scale;
GUEST_SYNC(8);
GUEST_ASSERT(tsc_page->tsc_offset == tsc_offset);
GUEST_ASSERT(tsc_page->tsc_scale == tsc_scale);

GUEST_SYNC(9);

check_tsc_msr_tsc_page(tsc_page);

/*
* Disable re-enlightenment and TSC page, check that KVM doesn't update
* it anymore.
*/
wrmsr(HV_X64_MSR_REENLIGHTENMENT_CONTROL, 0);
wrmsr(HV_X64_MSR_TSC_EMULATION_CONTROL, 0);
wrmsr(HV_X64_MSR_REFERENCE_TSC, 0);
memset(tsc_page, 0, sizeof(*tsc_page));

GUEST_SYNC(10);
GUEST_ASSERT(tsc_page->tsc_sequence == 0);
GUEST_ASSERT(tsc_page->tsc_offset == 0);
GUEST_ASSERT(tsc_page->tsc_scale == 0);

GUEST_DONE();
}

#define VCPU_ID 0

static void host_check_tsc_msr_rdtsc(struct kvm_vm *vm)
{
u64 tsc_freq, r1, r2, t1, t2;
s64 delta_ns;

tsc_freq = vcpu_get_msr(vm, VCPU_ID, HV_X64_MSR_TSC_FREQUENCY);
TEST_ASSERT(tsc_freq > 0, "TSC frequency must be nonzero");

/* First, check MSR-based clocksource */
r1 = rdtsc();
t1 = vcpu_get_msr(vm, VCPU_ID, HV_X64_MSR_TIME_REF_COUNT);
nop_loop();
r2 = rdtsc();
t2 = vcpu_get_msr(vm, VCPU_ID, HV_X64_MSR_TIME_REF_COUNT);

TEST_ASSERT(t2 > t1, "Time reference MSR is not monotonic (%ld <= %ld)", t1, t2);

/* HV_X64_MSR_TIME_REF_COUNT is in 100ns */
delta_ns = ((t2 - t1) * 100) - ((r2 - r1) * 1000000000 / tsc_freq);
if (delta_ns < 0)
delta_ns = -delta_ns;

/* 1% tolerance */
TEST_ASSERT(delta_ns * 100 < (t2 - t1) * 100,
"Elapsed time does not match (MSR=%ld, TSC=%ld)",
(t2 - t1) * 100, (r2 - r1) * 1000000000 / tsc_freq);
}

int main(void)
{
struct kvm_vm *vm;
struct kvm_run *run;
struct ucall uc;
vm_vaddr_t tsc_page_gva;
int stage;

vm = vm_create_default(VCPU_ID, 0, guest_main);
run = vcpu_state(vm, VCPU_ID);

vcpu_set_hv_cpuid(vm, VCPU_ID);

tsc_page_gva = vm_vaddr_alloc(vm, getpagesize(), 0x10000, 0, 0);
memset(addr_gpa2hva(vm, tsc_page_gva), 0x0, getpagesize());
TEST_ASSERT((addr_gva2gpa(vm, tsc_page_gva) & (getpagesize() - 1)) == 0,
"TSC page has to be page aligned\n");
vcpu_args_set(vm, VCPU_ID, 2, tsc_page_gva, addr_gva2gpa(vm, tsc_page_gva));

host_check_tsc_msr_rdtsc(vm);

for (stage = 1;; stage++) {
_vcpu_run(vm, VCPU_ID);
TEST_ASSERT(run->exit_reason == KVM_EXIT_IO,
"Stage %d: unexpected exit reason: %u (%s),\n",
stage, run->exit_reason,
exit_reason_str(run->exit_reason));

switch (get_ucall(vm, VCPU_ID, &uc)) {
case UCALL_ABORT:
TEST_FAIL("%s at %s:%ld", (const char *)uc.args[0],
__FILE__, uc.args[1]);
/* NOT REACHED */
case UCALL_SYNC:
break;
case UCALL_DONE:
/* Keep in sync with guest_main() */
TEST_ASSERT(stage == 11, "Testing ended prematurely, stage %d\n",
stage);
goto out;
default:
TEST_FAIL("Unknown ucall %lu", uc.cmd);
}

TEST_ASSERT(!strcmp((const char *)uc.args[0], "hello") &&
uc.args[1] == stage,
"Stage %d: Unexpected register values vmexit, got %lx",
stage, (ulong)uc.args[1]);

/* Reset kvmclock triggering TSC page update */
if (stage == 7 || stage == 8 || stage == 10) {
struct kvm_clock_data clock = {0};

vm_ioctl(vm, KVM_SET_CLOCK, &clock);
}
}

out:
kvm_vm_free(vm);
}

0 comments on commit 2c7f76b

Please sign in to comment.