This patch can fix the bug. I tried kvm-unit-tests vmx with your patch ten times on Ice lake and Cooper lake and the failure didn't happen. Thanks Jim!
-----Original Message-----
From: Jim Mattson <jmattson@xxxxxxxxxx>
Sent: Wednesday, June 29, 2022 10:57 AM
To: kvm@xxxxxxxxxxxxxxx; pbonzini@xxxxxxxxxx; Yang, Lixiao <lixiao.yang@xxxxxxxxx>; nadav.amit@xxxxxxxxx
Cc: Jim Mattson <jmattson@xxxxxxxxxx>
Subject: [kvm-unit-tests PATCH] x86: VMX: Fix the VMX-preemption timer expiration test
When the VMX-preemption timer fires between the test for
"vmx_get_test_stage() == 0" and the subsequent rdtsc instruction, the final VM-entry to finish the guest will inadvertently update vmx_preemption_timer_expiry_finish.
Move the code to finish the guest until after the calculations involving vmx_preemption_timer_expiry_finish are done, so that it doesn't matter if vmx_preemption_timer_expiry_finish is clobbered.
Signed-off-by: Jim Mattson <jmattson@xxxxxxxxxx>
Fixes: b49a1a6d4e23 ("x86: VMX: Add a VMX-preemption timer expiration test")
---
x86/vmx_tests.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/x86/vmx_tests.c b/x86/vmx_tests.c index 4d581e7085ea..8a1393668d93 100644
--- a/x86/vmx_tests.c
+++ b/x86/vmx_tests.c
@@ -9194,16 +9194,16 @@ static void vmx_preemption_timer_expiry_test(void)
reason = (u32)vmcs_read(EXI_REASON);
TEST_ASSERT(reason == VMX_PREEMPT);
- vmcs_clear_bits(PIN_CONTROLS, PIN_PREEMPT);
- vmx_set_test_stage(1);
- enter_guest();
-
tsc_deadline = ((vmx_preemption_timer_expiry_start >> misc.pt_bit) <<
misc.pt_bit) + (preemption_timer_value << misc.pt_bit);
report(vmx_preemption_timer_expiry_finish < tsc_deadline,
"Last stored guest TSC (%lu) < TSC deadline (%lu)",
vmx_preemption_timer_expiry_finish, tsc_deadline);
+
+ vmcs_clear_bits(PIN_CONTROLS, PIN_PREEMPT);
+ vmx_set_test_stage(1);
+ enter_guest();
}
static void vmx_db_test_guest(void)
--
2.37.0.rc0.161.g10f37bed90-goog
