From: Like Xu <likexu@xxxxxxxxxxx>
The check_emulated_instr() testcase fails when the KVM module parameter
"force_emulation_prefix" is 1. The root cause is that the value written by
the counter exceeds the maximum bit width of the GP counter.
Signed-off-by: Like Xu <likexu@xxxxxxxxxxx>
---
x86/pmu.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/x86/pmu.c b/x86/pmu.c
index 356d589..4dbbe71 100644
--- a/x86/pmu.c
+++ b/x86/pmu.c
@@ -477,6 +477,7 @@ static void check_running_counter_wrmsr(void)
static void check_emulated_instr(void)
{
uint64_t status, instr_start, brnch_start;
+ uint64_t gp_counter_width = (1ull << pmu.gp_counter_width) - 1;
unsigned int branch_idx = pmu.is_intel ? 5 : 2;
pmu_counter_t brnch_cnt = {
.ctr = MSR_GP_COUNTERx(0),
@@ -498,8 +499,8 @@ static void check_emulated_instr(void)
brnch_start = -EXPECTED_BRNCH;
instr_start = -EXPECTED_INSTR;
- wrmsr(MSR_GP_COUNTERx(0), brnch_start);
- wrmsr(MSR_GP_COUNTERx(1), instr_start);
+ wrmsr(MSR_GP_COUNTERx(0), brnch_start & gp_counter_width);
+ wrmsr(MSR_GP_COUNTERx(1), instr_start & gp_counter_width);
// KVM_FEP is a magic prefix that forces emulation so
// 'KVM_FEP "jne label\n"' just counts as a single instruction.
asm volatile(
--
2.39.0
