kvm-unit-tests: VMX: Test suite for preemption timer

PATCH Superseded Arthur Chunqi Li 2 participants 5 messages Sep 4, 2013 – Sep 9, 2013 KVM

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Arthur Chunqi Li

author

2013-09-04 15:26 UTC #0 lore raw

PATCH 1/1 kvm-unit-tests: VMX: Test suite for preemption timer

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.

Signed-off-by Arthur Chunqi Li <[email protected]>

---
 x86/vmx.h       |    3 ++
 x86/vmx_tests.c |  117 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 120 insertions(+)

x86/vmx.h +3 -0

index 28595d8..ebc8cfd 100644
@@ -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 {

x86/vmx_tests.c +117 -0

132 lines not on this page · raw message

Signature · 1 line

1.7.9.5

Arthur Chunqi Li

author

2013-09-05 09:22 UTC #1 lore raw

Hi Jan, Gleb and Paolo,

It suddenly occurred to me that, if guest's PIN_PREEMPT disabled while EXI_SAVE_PREEMPT_VALUE enabled, what will happen? The preempt value in vmcs will not be affected, yes?

This cases fails to test in this patch.

Arthur

Quoted 182 lines · Arthur Chunqi Li

Signed-off-by Arthur Chunqi Li <[email protected]>

---
 x86/vmx.h       |    3 ++
 x86/vmx_tests.c |  117 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 120 insertions(+)

x86/vmx.h +3 -0

index 28595d8..ebc8cfd 100644
@@ -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 {

x86/vmx_tests.c +117 -1

index c1b39f4..d358148 100644
@@ -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 +102,95 @@ 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_pin;
+
+       ctrl_pin = vmcs_read(PIN_CONTROLS) | PIN_PREEMPT;
+       ctrl_pin &= ctrl_pin_rev.clr;
+       vmcs_write(PIN_CONTROLS, ctrl_pin);
+       preempt_val = 10000000;
+       vmcs_write(PREEMPT_TIMER_VALUE, preempt_val);
+       preempt_scale = rdmsr(MSR_IA32_VMX_MISC) & 0x1F;
+}
+
+void preemption_timer_main()
+{
+       tsc_val = rdtsc();
+       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 {
+               set_stage(0);
+               vmcall();
+               if (get_stage() == 1)
+                       vmcall();
+       }
+       while (1) {
+               if (((rdtsc() - tsc_val) >> preempt_scale)
+                               > 10 * preempt_val) {
+                       report("Preemption timer", 0);
+                       break;
+               }
+       }
+}
+
+int preemption_timer_exit_handler()
+{
+       u64 guest_rip;
+       ulong reason;
+       u32 insn_len;
+       u32 ctrl_exit;
+
+       guest_rip = vmcs_read(GUEST_RIP);
+       reason = vmcs_read(EXI_REASON) & 0xff;
+       insn_len = vmcs_read(EXI_INST_LEN);
+       switch (reason) {
+       case VMX_PREEMPT:
+               if (((rdtsc() - tsc_val) >> preempt_scale) < preempt_val)
+                       report("Preemption timer", 0);
+               else
+                       report("Preemption timer", 1);
+               return VMX_TEST_VMEXIT;
+       case VMX_VMCALL:
+               switch (get_stage()) {
+               case 0:
+                       if (vmcs_read(PREEMPT_TIMER_VALUE) != preempt_val)
+                               report("Save preemption value", 0);
+                       else {
+                               set_stage(get_stage() + 1);
+                               ctrl_exit = (vmcs_read(EXI_CONTROLS) |
+                                       EXI_SAVE_PREEMPT) & ctrl_exit_rev.clr;
+                               vmcs_write(EXI_CONTROLS, ctrl_exit);
+                       }
+                       break;
+               case 1:
+                       if (vmcs_read(PREEMPT_TIMER_VALUE) >= preempt_val)
+                               report("Save preemption value", 0);
+                       else
+                               report("Save preemption value", 1);
+                       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 +198,7 @@ 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

Signature · 5 lines

Arthur Chunqi Li
Department of Computer Science
School of EECS
Peking University
Beijing, China

Paolo Bonzini

maintainer

2013-09-09 12:51 UTC #2 lore raw

Il 05/09/2013 11:22, Arthur Chunqi Li ha scritto:

Quoted 5 lines

Hi Jan, Gleb and Paolo,
It suddenly occurred to me that, if guest's PIN_PREEMPT disabled while EXI_SAVE_PREEMPT_VALUE enabled, what will happen? The preempt value in vmcs will not be affected, yes?

Indeed. The VMX preemption timer will not count down, so it will remain set to the same value. Saving it on exit will actually do nothing.

Quoted 1 line

This cases fails to test in this patch.

You can add it as a follow up.

Paolo

Arthur Chunqi Li

author

2013-09-09 12:53 UTC #3 lore raw

Quoted 7 lines · Paolo Bonzini

Il 05/09/2013 11:22, Arthur Chunqi Li ha scritto:
Quoted 5 lines
Hi Jan, Gleb and Paolo,
It suddenly occurred to me that, if guest's PIN_PREEMPT disabled while EXI_SAVE_PREEMPT_VALUE enabled, what will happen? The preempt value in vmcs will not be affected, yes?

Quoted 6 lines

Indeed. The VMX preemption timer will not count down, so it will remain set to the same value. Saving it on exit will actually do nothing.
Quoted 1 line
This cases fails to test in this patch.
You can add it as a follow up.

Yep. Because this patch was committed several weeks ago, I have committed a second version, you can just review that patch.

Arthur

Quoted 3 lines

Paolo

Signature · 5 lines

Arthur Chunqi Li
Department of Computer Science
School of EECS
Peking University
Beijing, China

Paolo Bonzini

maintainer Reviewed-by on v1 1/1

2013-09-09 12:47 UTC #4 lore raw

In reply to Arthur Chunqi Li

Il 04/09/2013 17:26, Arthur Chunqi Li ha scritto:

Quoted 11 lines

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.
Signed-off-by Arthur Chunqi Li <[email protected]>
---
 x86/vmx.h       |    3 ++
 x86/vmx_tests.c |  117 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 120 insertions(+)

Please rebase your other four patches on top of this one, since this one is good to go!

Reviewed-by Paolo Bonzini <[email protected]>

Paolo

Quoted 97 lines

x86/vmx_tests.c +87 -0

+void preemption_timer_init()
+{
+	u32 ctrl_pin;
+
+	ctrl_pin = vmcs_read(PIN_CONTROLS) | PIN_PREEMPT;
+	ctrl_pin &= ctrl_pin_rev.clr;
+	vmcs_write(PIN_CONTROLS, ctrl_pin);
+	preempt_val = 10000000;
+	vmcs_write(PREEMPT_TIMER_VALUE, preempt_val);
+	preempt_scale = rdmsr(MSR_IA32_VMX_MISC) & 0x1F;
+}
+
+void preemption_timer_main()
+{
+	tsc_val = rdtsc();
+	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 {
+		set_stage(0);
+		vmcall();
+		if (get_stage() == 1)
+			vmcall();
+	}
+	while (1) {
+		if (((rdtsc() - tsc_val) >> preempt_scale)
+				> 10 * preempt_val) {
+			report("Preemption timer", 0);
+			break;
+		}
+	}
+}
+
+int preemption_timer_exit_handler()
+{
+	u64 guest_rip;
+	ulong reason;
+	u32 insn_len;
+	u32 ctrl_exit;
+
+	guest_rip = vmcs_read(GUEST_RIP);
+	reason = vmcs_read(EXI_REASON) & 0xff;
+	insn_len = vmcs_read(EXI_INST_LEN);
+	switch (reason) {
+	case VMX_PREEMPT:
+		if (((rdtsc() - tsc_val) >> preempt_scale) < preempt_val)
+			report("Preemption timer", 0);
+		else
+			report("Preemption timer", 1);
+		return VMX_TEST_VMEXIT;
+	case VMX_VMCALL:
+		switch (get_stage()) {
+		case 0:
+			if (vmcs_read(PREEMPT_TIMER_VALUE) != preempt_val)
+				report("Save preemption value", 0);
+			else {
+				set_stage(get_stage() + 1);
+				ctrl_exit = (vmcs_read(EXI_CONTROLS) |
+					EXI_SAVE_PREEMPT) & ctrl_exit_rev.clr;
+				vmcs_write(EXI_CONTROLS, ctrl_exit);
+			}
+			break;
+		case 1:
+			if (vmcs_read(PREEMPT_TIMER_VALUE) >= preempt_val)
+				report("Save preemption value", 0);
+			else
+				report("Save preemption value", 1);
+			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 +198,7 @@ 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} },
 };