When IA32_TSC is on the VM-exit MSR-store list, the value saved is not
subject to the "use TSC offsetting" VM-execution control for the
current VMCS.
Prior to commit e79f245ddec17 ("X86/KVM: Properly update 'tsc_offset'
to represent the running guest"), kvm did not handle this situation
properly.
Signed-off-by: Jim Mattson <jmattson@xxxxxxxxxx>
Reviewed-by: Marc Orr <marcorr@xxxxxxxxxx>
Reviewed-by: Peter Shier <pshier@xxxxxxxxxx>
---
x86/unittests.cfg | 6 ++++++
x86/vmx.h | 1 +
x86/vmx_tests.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 52 insertions(+)
diff --git a/x86/unittests.cfg b/x86/unittests.cfg
index 3b21a85..9448409 100644
--- a/x86/unittests.cfg
+++ b/x86/unittests.cfg
@@ -572,6 +572,12 @@ extra_params = -cpu host,+vmx -m 2560 -append vmx_pending_event_hlt_test
arch = x86_64
groups = vmx
+[vmx_store_tsc_test]
+file = vmx.flat
+extra_params = -cpu host,+vmx -m 2560 -append vmx_store_tsc_test
+arch = x86_64
+groups = vmx
+
[vmx_db_test]
file = vmx.flat
extra_params = -cpu host,+vmx -m 2560 -append vmx_db_test
diff --git a/x86/vmx.h b/x86/vmx.h
index ba47455..8a00f73 100644
--- a/x86/vmx.h
+++ b/x86/vmx.h
@@ -384,6 +384,7 @@ enum Ctrl_pin {
enum Ctrl0 {
CPU_INTR_WINDOW = 1ul << 2,
+ CPU_USE_TSC_OFFSET = 1ul << 3,
CPU_HLT = 1ul << 7,
CPU_INVLPG = 1ul << 9,
CPU_MWAIT = 1ul << 10,
diff --git a/x86/vmx_tests.c b/x86/vmx_tests.c
index b105b23..d223dea 100644
--- a/x86/vmx_tests.c
+++ b/x86/vmx_tests.c
@@ -5031,6 +5031,50 @@ static void vmx_pending_event_hlt_test(void)
vmx_pending_event_test_core(true);
}
+#define GUEST_TSC_OFFSET (1u << 30)
+
+static u64 guest_tsc;
+
+static void vmx_store_tsc_test_guest(void)
+{
+ guest_tsc = rdtsc();
+}
+
+/*
+ * This test ensures that when IA32_TSC is in the VM-exit MSR-store
+ * list, the value saved is not subject to the TSC offset that is
+ * applied to RDTSC/RDTSCP/RDMSR(IA32_TSC) in guest execution.
+ */
+static void vmx_store_tsc_test(void)
+{
+ struct vmx_msr_entry msr_entry = { .index = MSR_IA32_TSC };
+ u64 low, high;
+
+ if (!(ctrl_cpu_rev[0].clr & CPU_USE_TSC_OFFSET)) {
+ printf("\t'Use TSC offsetting' not supported.\n");
+ return;
+ }
+
+ test_set_guest(vmx_store_tsc_test_guest);
+
+ vmcs_set_bits(CPU_EXEC_CTRL0, CPU_USE_TSC_OFFSET);
+ vmcs_write(EXI_MSR_ST_CNT, 1);
+ vmcs_write(EXIT_MSR_ST_ADDR, virt_to_phys(&msr_entry));
+ vmcs_write(TSC_OFFSET, GUEST_TSC_OFFSET);
+
+ low = rdtsc();
+ enter_guest();
+ high = rdtsc();
+
+ report("RDTSC value in the guest (%lu) is in range [%lu, %lu]",
+ low + GUEST_TSC_OFFSET <= guest_tsc &&
+ guest_tsc <= high + GUEST_TSC_OFFSET,
+ guest_tsc, low + GUEST_TSC_OFFSET, high + GUEST_TSC_OFFSET);
+ report("IA32_TSC value saved in the VM-exit MSR-store list (%lu) is in range [%lu, %lu]",
+ low <= msr_entry.value && msr_entry.value <= high,
+ msr_entry.value, low, high);
+}
+
static void vmx_db_test_guest(void)
{
/*
@@ -5835,6 +5879,7 @@ struct vmx_test vmx_tests[] = {
TEST(vmx_db_test),
TEST(vmx_pending_event_test),
TEST(vmx_pending_event_hlt_test),
+ TEST(vmx_store_tsc_test),
/* EPT access tests. */
TEST(ept_access_test_not_present),
TEST(ept_access_test_read_only),
--
2.19.1.930.g4563a0d9d0-goog
