Test cases for preemption timer in nested VMX. Two aspects are tested:
1. Save preemption timer on VMEXIT if relevant bit set in EXIT_CONTROL
2. Test a relevant bug of KVM. The bug will not save preemption timer
value if exit L2->L0 for some reason and enter L0->L2. Thus preemption
timer will never trigger if the value is large enough.
3. Some other aspects are tested, e.g. preempt without save, preempt
when value is 0.
Signed-off-by: Arthur Chunqi Li <yzt356@xxxxxxxxx>
---
ChangeLog to v1:
1. Add test of EXI_SAVE_PREEMPT enable and PIN_PREEMPT disable
2. Add test of PIN_PREEMPT enable and EXI_SAVE_PREEMPT enable/disable
3. Add test of preemption value is 0
x86/vmx.h | 3 +
x86/vmx_tests.c | 175 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 178 insertions(+)
diff --git a/x86/vmx.h b/x86/vmx.h
index 28595d8..ebc8cfd 100644
--- a/x86/vmx.h
+++ b/x86/vmx.h
@@ -210,6 +210,7 @@ enum Encoding {
GUEST_ACTV_STATE = 0x4826ul,
GUEST_SMBASE = 0x4828ul,
GUEST_SYSENTER_CS = 0x482aul,
+ PREEMPT_TIMER_VALUE = 0x482eul,
/* 32-Bit Host State Fields */
HOST_SYSENTER_CS = 0x4c00ul,
@@ -331,6 +332,7 @@ enum Ctrl_exi {
EXI_LOAD_PERF = 1UL << 12,
EXI_INTA = 1UL << 15,
EXI_LOAD_EFER = 1UL << 21,
+ EXI_SAVE_PREEMPT = 1UL << 22,
};
enum Ctrl_ent {
@@ -342,6 +344,7 @@ enum Ctrl_pin {
PIN_EXTINT = 1ul << 0,
PIN_NMI = 1ul << 3,
PIN_VIRT_NMI = 1ul << 5,
+ PIN_PREEMPT = 1ul << 6,
};
enum Ctrl0 {
diff --git a/x86/vmx_tests.c b/x86/vmx_tests.c
index c1b39f4..2e32031 100644
--- a/x86/vmx_tests.c
+++ b/x86/vmx_tests.c
@@ -1,4 +1,30 @@
#include "vmx.h"
+#include "msr.h"
+#include "processor.h"
+
+volatile u32 stage;
+
+static inline void vmcall()
+{
+ asm volatile("vmcall");
+}
+
+static inline void set_stage(u32 s)
+{
+ barrier();
+ stage = s;
+ barrier();
+}
+
+static inline u32 get_stage()
+{
+ u32 s;
+
+ barrier();
+ s = stage;
+ barrier();
+ return s;
+}
void basic_init()
{
@@ -76,6 +102,153 @@ int vmenter_exit_handler()
return VMX_TEST_VMEXIT;
}
+u32 preempt_scale;
+volatile unsigned long long tsc_val;
+volatile u32 preempt_val;
+
+void preemption_timer_init()
+{
+ u32 ctrl_exit;
+
+ // Enable EXI_SAVE_PREEMPT with PIN_PREEMPT dieabled
+ ctrl_exit = (vmcs_read(EXI_CONTROLS) |
+ EXI_SAVE_PREEMPT) & ctrl_exit_rev.clr;
+ vmcs_write(EXI_CONTROLS, ctrl_exit);
+ preempt_val = 10000000;
+ vmcs_write(PREEMPT_TIMER_VALUE, preempt_val);
+ set_stage(0);
+ preempt_scale = rdmsr(MSR_IA32_VMX_MISC) & 0x1F;
+}
+
+void preemption_timer_main()
+{
+ int i, j;
+
+ if (!(ctrl_pin_rev.clr & PIN_PREEMPT)) {
+ printf("\tPreemption timer is not supported\n");
+ return;
+ }
+ if (!(ctrl_exit_rev.clr & EXI_SAVE_PREEMPT))
+ printf("\tSave preemption value is not supported\n");
+ else {
+ // Test EXI_SAVE_PREEMPT enable and PIN_PREEMPT disable
+ set_stage(0);
+ // Consume enough time to let L2->L0->L2 occurs
+ for(i = 0; i < 100000; i++)
+ for (j = 0; j < 10000; j++);
+ vmcall();
+ // Test PIN_PREEMPT enable and EXI_SAVE_PREEMPT enable/disable
+ set_stage(1);
+ vmcall();
+ // Test both enable
+ if (get_stage() == 2)
+ vmcall();
+ }
+ // Test the bug of reseting preempt value when L2->L0->L2
+ set_stage(3);
+ vmcall();
+ tsc_val = rdtsc();
+ while (1) {
+ if (((rdtsc() - tsc_val) >> preempt_scale)
+ > 10 * preempt_val) {
+ report("Preemption timer timeout", 0);
+ break;
+ }
+ if (get_stage() == 4)
+ break;
+ }
+ // Test preempt val is 0
+ set_stage(4);
+ report("Preemption timer, val=0", 0);
+}
+
+int preemption_timer_exit_handler()
+{
+ u64 guest_rip;
+ ulong reason;
+ u32 insn_len;
+ u32 ctrl_exit;
+ u32 ctrl_pin;
+
+ guest_rip = vmcs_read(GUEST_RIP);
+ reason = vmcs_read(EXI_REASON) & 0xff;
+ insn_len = vmcs_read(EXI_INST_LEN);
+ switch (reason) {
+ case VMX_PREEMPT:
+ switch (get_stage()) {
+ case 3:
+ if (((rdtsc() - tsc_val) >> preempt_scale) < preempt_val)
+ report("Preemption timer timeout", 0);
+ else
+ report("Preemption timer timeout", 1);
+ set_stage(get_stage() + 1);
+ break;
+ case 4:
+ if (vmcs_read(PREEMPT_TIMER_VALUE) == 0)
+ report("Preemption timer, val=0", 1);
+ else
+ report("Preemption timer, val=0", 0);
+ return VMX_TEST_VMEXIT;
+ }
+ return VMX_TEST_RESUME;
+ case VMX_VMCALL:
+ switch (get_stage()) {
+ case 0:
+ if (vmcs_read(PREEMPT_TIMER_VALUE) != preempt_val)
+ report("Preemption timer off", 0);
+ else
+ report("Preemption timer off", 1);
+ // Enable PIN_PREEMPT and disable EXI_SAVE_PREEMPT
+ ctrl_pin = (vmcs_read(PIN_CONTROLS) | PIN_PREEMPT) &
+ ctrl_pin_rev.clr;
+ vmcs_write(PIN_CONTROLS, ctrl_pin);
+ ctrl_exit = (vmcs_read(EXI_CONTROLS) &
+ ~EXI_SAVE_PREEMPT) & ctrl_exit_rev.clr;
+ vmcs_write(EXI_CONTROLS, ctrl_exit);
+ vmcs_write(PREEMPT_TIMER_VALUE, preempt_val);
+ break;
+ case 1:
+ if (vmcs_read(PREEMPT_TIMER_VALUE) != preempt_val)
+ report("Save preemption value", 0);
+ else {
+ set_stage(get_stage() + 1);
+ // Enable EXI_SAVE_PREEMPT with PIN_PREEMPT
+ // already enabled
+ ctrl_exit = (vmcs_read(EXI_CONTROLS) |
+ EXI_SAVE_PREEMPT) & ctrl_exit_rev.clr;
+ vmcs_write(EXI_CONTROLS, ctrl_exit);
+ }
+ vmcs_write(PREEMPT_TIMER_VALUE, preempt_val);
+ break;
+ case 2:
+ if (vmcs_read(PREEMPT_TIMER_VALUE) >= preempt_val)
+ report("Save preemption value", 0);
+ else
+ report("Save preemption value", 1);
+ break;
+ case 3:
+ vmcs_write(PREEMPT_TIMER_VALUE, preempt_val);
+ ctrl_pin = (vmcs_read(PIN_CONTROLS) | PIN_PREEMPT) &
+ ctrl_pin_rev.clr;
+ vmcs_write(PIN_CONTROLS, ctrl_pin);
+ ctrl_exit = (vmcs_read(EXI_CONTROLS) |
+ EXI_SAVE_PREEMPT) & ctrl_exit_rev.clr;
+ vmcs_write(EXI_CONTROLS, ctrl_exit);
+ break;
+ default:
+ printf("Invalid stage.\n");
+ print_vmexit_info();
+ return VMX_TEST_VMEXIT;
+ }
+ vmcs_write(GUEST_RIP, guest_rip + insn_len);
+ return VMX_TEST_RESUME;
+ default:
+ printf("Unknown exit reason, %d\n", reason);
+ print_vmexit_info();
+ }
+ return VMX_TEST_VMEXIT;
+}
+
/* name/init/guest_main/exit_handler/syscall_handler/guest_regs
basic_* just implement some basic functions */
struct vmx_test vmx_tests[] = {
@@ -83,5 +256,7 @@ struct vmx_test vmx_tests[] = {
basic_syscall_handler, {0} },
{ "vmenter", basic_init, vmenter_main, vmenter_exit_handler,
basic_syscall_handler, {0} },
+ { "preemption timer", preemption_timer_init, preemption_timer_main,
+ preemption_timer_exit_handler, basic_syscall_handler, {0} },
{ NULL, NULL, NULL, NULL, NULL, {0} },
};
--
1.7.9.5
--
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