On 13/11/2021 7:56 am, Jim Mattson wrote:
Add tests of "instructions retired" and "branch instructions retired,"
to ensure that these events count emulated instructions.
Signed-off-by: Eric Hankland <ehankland@xxxxxxxxxx>
[jmattson:
- Added command-line parameter to conditionally run the new tests.
- Added pmu-emulation test to unittests.cfg
]
Signed-off-by: Jim Mattson <jmattson@xxxxxxxxxx>
---
x86/pmu.c | 80 +++++++++++++++++++++++++++++++++++++++++++++++
x86/unittests.cfg | 7 +++++
2 files changed, 87 insertions(+)
diff --git a/x86/pmu.c b/x86/pmu.c
index ec61ac956a55..a159333b0c73 100644
--- a/x86/pmu.c
+++ b/x86/pmu.c
@@ -33,6 +33,12 @@
#define N 1000000
+#define KVM_FEP "ud2; .byte 'k', 'v', 'm';"
+// These values match the number of instructions and branches in the
+// assembly block in check_emulated_instr().
+#define EXPECTED_INSTR 17
+#define EXPECTED_BRNCH 5
+
typedef struct {
uint32_t ctr;
uint32_t config;
@@ -468,6 +474,77 @@ static void check_running_counter_wrmsr(void)
report_prefix_pop();
}
+static void check_emulated_instr(void)
+{
+ uint64_t status, instr_start, brnch_start;
+ pmu_counter_t brnch_cnt = {
+ .ctr = MSR_IA32_PERFCTR0,
+ /* branch instructions */
+ .config = EVNTSEL_OS | EVNTSEL_USR | gp_events[5].unit_sel,
+ .count = 0,
+ };
+ pmu_counter_t instr_cnt = {
+ .ctr = MSR_IA32_PERFCTR0 + 1,
+ /* instructions */
+ .config = EVNTSEL_OS | EVNTSEL_USR | gp_events[1].unit_sel,
+ .count = 0,
+ };
+ report_prefix_push("emulated instruction");
+
+ wrmsr(MSR_CORE_PERF_GLOBAL_OVF_CTRL,
+ rdmsr(MSR_CORE_PERF_GLOBAL_STATUS));
+
+ start_event(&brnch_cnt);
+ start_event(&instr_cnt);
+
+ brnch_start = -EXPECTED_BRNCH;
+ instr_start = -EXPECTED_INSTR;
+ wrmsr(MSR_IA32_PERFCTR0, brnch_start);
+ wrmsr(MSR_IA32_PERFCTR0 + 1, instr_start);
+ // KVM_FEP is a magic prefix that forces emulation so
+ // 'KVM_FEP "jne label\n"' just counts as a single instruction.
+ asm volatile(
+ "mov $0x0, %%eax\n"
+ "cmp $0x0, %%eax\n"
+ KVM_FEP "jne label\n"
+ KVM_FEP "jne label\n"
+ KVM_FEP "jne label\n"
+ KVM_FEP "jne label\n"
+ KVM_FEP "jne label\n"
+ "mov $0xa, %%eax\n"
+ "cpuid\n"
+ "mov $0xa, %%eax\n"
+ "cpuid\n"
+ "mov $0xa, %%eax\n"
+ "cpuid\n"
+ "mov $0xa, %%eax\n"
+ "cpuid\n"
+ "mov $0xa, %%eax\n"
+ "cpuid\n"
+ "label:\n"
+ :
+ :
+ : "eax", "ebx", "ecx", "edx");
+
+ wrmsr(MSR_CORE_PERF_GLOBAL_CTRL, 0);
+
+ stop_event(&brnch_cnt);
+ stop_event(&instr_cnt);
+
+ // Check that the end count - start count is at least the expected
+ // number of instructions and branches.
+ report(instr_cnt.count - instr_start >= EXPECTED_INSTR,
+ "instruction count");
+ report(brnch_cnt.count - brnch_start >= EXPECTED_BRNCH,
+ "branch count");
+ // Additionally check that those counters overflowed properly.
+ status = rdmsr(MSR_CORE_PERF_GLOBAL_STATUS);
+ report(status & 1, "instruction counter overflow");
+ report(status & 2, "branch counter overflow");
+
+ report_prefix_pop();
+}
+
static void check_counters(void)
{
check_gp_counters();
@@ -563,6 +640,9 @@ int main(int ac, char **av)
check_counters();
+ if (ac > 1 && !strcmp(av[1], "emulation"))
+ check_emulated_instr();
+
if (rdmsr(MSR_IA32_PERF_CAPABILITIES) & PMU_CAP_FW_WRITES) {
gp_counter_base = MSR_IA32_PMC0;
report_prefix_push("full-width writes");
diff --git a/x86/unittests.cfg b/x86/unittests.cfg
index 3000e53c790f..2aedb24dc4ff 100644
--- a/x86/unittests.cfg
+++ b/x86/unittests.cfg
@@ -185,6 +185,13 @@ extra_params = -cpu host,migratable=no
check = /sys/module/kvm/parameters/ignore_msrs=N
check = /proc/sys/kernel/nmi_watchdog=0
+[pmu_emulation]
+file = pmu.flat
+arch = x86_64
+extra_params = -cpu max -append emulation
+check = /sys/module/kvm_intel/parameters/force_emulation_prefix=Y
It's "/sys/module/kvm/parameters/force_emulation_prefix=Y",
If it's N, we need a output like "FAIL: check_emulated_instr"
rather than:
Unhandled exception 6 #UD at ip 0000000000401387
error_code=0000 rflags=00010046 cs=00000008
rax=0000000000000000 rcx=00000000000000c2 rdx=00000000ffffffff rbx=00000000009509f4
rbp=0000000000513730 rsi=0000000000000020 rdi=0000000000000034
r8=0000000000000000 r9=0000000000000020 r10=000000000000000d r11=0000000000000000
r12=000000000000038e r13=0000000000000002 r14=0000000000513d80 r15=0000000000008603
cr0=0000000080010011 cr2=0000000000000000 cr3=0000000001007000 cr4=0000000000000020
cr8=0000000000000000
STACK: @401387 400384
+check = /proc/sys/kernel/nmi_watchdog=0
+
[vmware_backdoors]
file = vmware_backdoors.flat
extra_params = -machine vmport=on -cpu max
