[PATCH 0/2 v4] Fix VMX preemption timer migration

[PATCH 0/2 v4] Fix VMX preemption timer migration

[Makarand Sonare]

v2: Added an u32 flags to the kvm_vmx_nested_state_hdr to check the validity of
the preemption timer deadline. [Paolo]
v3: Moved the code to calculate timer value to a separate helper [Sean]
v3: Rename l1_scaled_tsc_value as l1_scaled_tsc. [Sean]
v3: Removed unncessary parenthesis and moved the >> operator to previous line [Sean]
v3: Changed >= to > for comparision between l1_scaled_tsc and
    vmx->nested.preemption_timer_deadline [Sean]
v3: Removed the extra if check in sync_vmcs02_to_vmcs12 [Sean]

Makarand Sonare (1):
  KVM: selftests: VMX preemption timer migration test

Peter Shier (1):
  KVM: nVMX: Fix VMX preemption timer migration

 Documentation/virt/kvm/api.rst                |   5 +
 arch/x86/include/uapi/asm/kvm.h               |   4 +
 arch/x86/kvm/vmx/nested.c                     |  58 +++-
 arch/x86/kvm/vmx/vmx.h                        |   2 +
 arch/x86/kvm/x86.c                            |   1 +
 include/uapi/linux/kvm.h                      |   1 +
 tools/arch/x86/include/uapi/asm/kvm.h         |   1 +
 tools/testing/selftests/kvm/.gitignore        |   1 +
 tools/testing/selftests/kvm/Makefile          |   1 +
 .../testing/selftests/kvm/include/kvm_util.h  |   2 +
 .../selftests/kvm/include/x86_64/processor.h  |  11 +-
 .../selftests/kvm/include/x86_64/vmx.h        |  27 ++
 .../kvm/x86_64/vmx_preemption_timer_test.c    | 255 ++++++++++++++++++
 13 files changed, 356 insertions(+), 13 deletions(-)
 create mode 100644 tools/testing/selftests/kvm/x86_64/vmx_preemption_timer_test.c

--
2.27.0.rc0.183.gde8f92d652-goog

[PATCH 1/2 v4] KVM: nVMX: Fix VMX preemption timer migration

[Makarand Sonare]

From: Peter Shier <pshier@google.com>

Add new field to hold preemption timer expiration deadline
appended to struct kvm_vmx_nested_state_hdr. This is to prevent
the first VM-Enter after migration from incorrectly restarting the timer
with the full timer value instead of partially decayed timer value.
KVM_SET_NESTED_STATE restarts timer using migrated state regardless
of whether L1 sets VM_EXIT_SAVE_VMX_PREEMPTION_TIMER.

Fixes: cf8b84f48a593 ("kvm: nVMX: Prepare for checkpointing L2 state")

Signed-off-by: Peter Shier <pshier@google.com>
Signed-off-by: Makarand Sonare <makarandsonare@google.com>
---
 Documentation/virt/kvm/api.rst  |  5 +++
 arch/x86/include/uapi/asm/kvm.h |  4 +++
 arch/x86/kvm/vmx/nested.c       | 58 ++++++++++++++++++++++++++++-----
 arch/x86/kvm/vmx/vmx.h          |  2 ++
 arch/x86/kvm/x86.c              |  1 +
 include/uapi/linux/kvm.h        |  1 +
 6 files changed, 62 insertions(+), 9 deletions(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index d871dacb984e9..a5ebe88cb7348 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -4326,6 +4326,9 @@ Errors:
   #define KVM_STATE_NESTED_RUN_PENDING		0x00000002
   #define KVM_STATE_NESTED_EVMCS		0x00000004

+  /* Available with KVM_CAP_NESTED_STATE_PREEMPTION_TIMER */
+  #define KVM_STATE_NESTED_PREEMPTION_TIMER	0x00000010
+
   #define KVM_STATE_NESTED_FORMAT_VMX		0
   #define KVM_STATE_NESTED_FORMAT_SVM		1

@@ -4335,8 +4338,10 @@ Errors:
   #define KVM_STATE_NESTED_VMX_SMM_VMXON	0x00000002

   struct kvm_vmx_nested_state_hdr {
+	__u32 flags;
 	__u64 vmxon_pa;
 	__u64 vmcs12_pa;
+	__u64 preemption_timer_deadline;

 	struct {
 		__u16 flags;
diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index 3f3f780c8c650..ae7ccb5e8747d 100644
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -391,6 +391,8 @@ struct kvm_sync_regs {
 #define KVM_STATE_NESTED_RUN_PENDING	0x00000002
 #define KVM_STATE_NESTED_EVMCS		0x00000004
 #define KVM_STATE_NESTED_MTF_PENDING	0x00000008
+/* Available with KVM_CAP_NESTED_STATE_PREEMPTION_TIMER */
+#define KVM_STATE_NESTED_PREEMPTION_TIMER	0x00000010

 #define KVM_STATE_NESTED_SMM_GUEST_MODE	0x00000001
 #define KVM_STATE_NESTED_SMM_VMXON	0x00000002
@@ -403,8 +405,10 @@ struct kvm_vmx_nested_state_data {
 };

 struct kvm_vmx_nested_state_hdr {
+	__u32 flags;
 	__u64 vmxon_pa;
 	__u64 vmcs12_pa;
+	__u64 preemption_timer_deadline;

 	struct {
 		__u16 flags;
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 51ebb60e1533a..a50cb99c4ed01 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -2092,9 +2092,29 @@ static enum hrtimer_restart vmx_preemption_timer_fn(struct hrtimer *timer)
 	return HRTIMER_NORESTART;
 }

-static void vmx_start_preemption_timer(struct kvm_vcpu *vcpu)
+static u64 vmx_calc_preemption_timer_value(struct kvm_vcpu *vcpu)
+{
+	struct vcpu_vmx *vmx = to_vmx(vcpu);
+	struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
+	u64 timer_value = 0;
+
+	u64 l1_scaled_tsc = kvm_read_l1_tsc(vcpu, rdtsc()) >>
+			    VMX_MISC_EMULATED_PREEMPTION_TIMER_RATE;
+
+	if (!vmx->nested.has_preemption_timer_deadline) {
+		timer_value = vmcs12->vmx_preemption_timer_value;
+		vmx->nested.preemption_timer_deadline = timer_value +
+							l1_scaled_tsc;
+		vmx->nested.has_preemption_timer_deadline = true;
+	} else if (l1_scaled_tsc < vmx->nested.preemption_timer_deadline)
+		timer_value = vmx->nested.preemption_timer_deadline -
+			      l1_scaled_tsc;
+	return timer_value;
+}
+
+static void vmx_start_preemption_timer(struct kvm_vcpu *vcpu,
+					u64 preemption_timeout)
 {
-	u64 preemption_timeout = get_vmcs12(vcpu)->vmx_preemption_timer_value;
 	struct vcpu_vmx *vmx = to_vmx(vcpu);

 	/*
@@ -3353,8 +3373,10 @@ enum nvmx_vmentry_status nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu,
 	 * the timer.
 	 */
 	vmx->nested.preemption_timer_expired = false;
-	if (nested_cpu_has_preemption_timer(vmcs12))
-		vmx_start_preemption_timer(vcpu);
+	if (nested_cpu_has_preemption_timer(vmcs12)) {
+		u64 timer_value = vmx_calc_preemption_timer_value(vcpu);
+		vmx_start_preemption_timer(vcpu, timer_value);
+	}

 	/*
 	 * Note no nested_vmx_succeed or nested_vmx_fail here. At this point
@@ -3462,6 +3484,7 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
 	 * the nested entry.
 	 */
 	vmx->nested.nested_run_pending = 1;
+	vmx->nested.has_preemption_timer_deadline = false;
 	status = nested_vmx_enter_non_root_mode(vcpu, true);
 	if (unlikely(status != NVMX_VMENTRY_SUCCESS))
 		goto vmentry_failed;
@@ -3962,9 +3985,10 @@ static void sync_vmcs02_to_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
 		vmcs12->guest_activity_state = GUEST_ACTIVITY_ACTIVE;

 	if (nested_cpu_has_preemption_timer(vmcs12) &&
-	    vmcs12->vm_exit_controls & VM_EXIT_SAVE_VMX_PREEMPTION_TIMER)
-			vmcs12->vmx_preemption_timer_value =
-				vmx_get_preemption_timer_value(vcpu);
+	    vmcs12->vm_exit_controls & VM_EXIT_SAVE_VMX_PREEMPTION_TIMER &&
+	    !vmx->nested.nested_run_pending)
+		vmcs12->vmx_preemption_timer_value =
+			vmx_get_preemption_timer_value(vcpu);

 	/*
 	 * In some cases (usually, nested EPT), L2 is allowed to change its
@@ -5896,8 +5920,10 @@ static int vmx_get_nested_state(struct kvm_vcpu *vcpu,
 		.flags = 0,
 		.format = KVM_STATE_NESTED_FORMAT_VMX,
 		.size = sizeof(kvm_state),
+		.hdr.vmx.flags = 0,
 		.hdr.vmx.vmxon_pa = -1ull,
 		.hdr.vmx.vmcs12_pa = -1ull,
+		.hdr.vmx.preemption_timer_deadline = 0,
 	};
 	struct kvm_vmx_nested_state_data __user *user_vmx_nested_state =
 		&user_kvm_nested_state->data.vmx[0];
@@ -5939,6 +5965,14 @@ static int vmx_get_nested_state(struct kvm_vcpu *vcpu,

 			if (vmx->nested.mtf_pending)
 				kvm_state.flags |= KVM_STATE_NESTED_MTF_PENDING;
+
+			if (nested_cpu_has_preemption_timer(vmcs12) &&
+			    vmx->nested.has_preemption_timer_deadline) {
+				kvm_state.hdr.vmx.flags |=
+					KVM_STATE_NESTED_PREEMPTION_TIMER;
+				kvm_state.hdr.vmx.preemption_timer_deadline =
+					vmx->nested.preemption_timer_deadline;
+			}
 		}
 	}

@@ -5984,7 +6018,6 @@ static int vmx_get_nested_state(struct kvm_vcpu *vcpu,
 				 get_shadow_vmcs12(vcpu), VMCS12_SIZE))
 			return -EFAULT;
 	}
-
 out:
 	return kvm_state.size;
 }
@@ -6056,7 +6089,8 @@ static int vmx_set_nested_state(struct kvm_vcpu *vcpu,
 	 */
 	if (is_smm(vcpu) ?
 		(kvm_state->flags &
-		 (KVM_STATE_NESTED_GUEST_MODE | KVM_STATE_NESTED_RUN_PENDING))
+		 (KVM_STATE_NESTED_GUEST_MODE | KVM_STATE_NESTED_RUN_PENDING |
+		  KVM_STATE_NESTED_PREEMPTION_TIMER))
 		: kvm_state->hdr.vmx.smm.flags)
 		return -EINVAL;

@@ -6146,6 +6180,12 @@ static int vmx_set_nested_state(struct kvm_vcpu *vcpu,
 			goto error_guest_mode;
 	}

+	if (kvm_state->hdr.vmx.flags & KVM_STATE_NESTED_PREEMPTION_TIMER) {
+		vmx->nested.has_preemption_timer_deadline = true;
+		vmx->nested.preemption_timer_deadline =
+			kvm_state->hdr.vmx.preemption_timer_deadline;
+	}
+
 	if (nested_vmx_check_controls(vcpu, vmcs12) ||
 	    nested_vmx_check_host_state(vcpu, vmcs12) ||
 	    nested_vmx_check_guest_state(vcpu, vmcs12, &ignored))
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index 298ddef79d009..672c28f17e497 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -169,6 +169,8 @@ struct nested_vmx {
 	u16 posted_intr_nv;

 	struct hrtimer preemption_timer;
+	u64 preemption_timer_deadline;
+	bool has_preemption_timer_deadline;
 	bool preemption_timer_expired;

 	/* to migrate it to L2 if VM_ENTRY_LOAD_DEBUG_CONTROLS is off */
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 471fccf7f8501..e73309879255c 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3418,6 +3418,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_MSR_PLATFORM_INFO:
 	case KVM_CAP_EXCEPTION_PAYLOAD:
 	case KVM_CAP_SET_GUEST_DEBUG:
+	case KVM_CAP_NESTED_STATE_PREEMPTION_TIMER:
 		r = 1;
 		break;
 	case KVM_CAP_SYNC_REGS:
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index ac9eba0289d1b..0868dce12a715 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1018,6 +1018,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_S390_PROTECTED 180
 #define KVM_CAP_PPC_SECURE_GUEST 181
 #define KVM_CAP_HALT_POLL 182
+#define KVM_CAP_NESTED_STATE_PREEMPTION_TIMER 183

 #ifdef KVM_CAP_IRQ_ROUTING

--
2.27.0.rc0.183.gde8f92d652-goog

[PATCH 2/2 v4] KVM: selftests: VMX preemption timer migration test

[Makarand Sonare]

When a nested VM with a VMX-preemption timer is migrated, verify that the
nested VM and its parent VM observe the VMX-preemption timer exit close to
the original expiration deadline.

Signed-off-by: Makarand Sonare <makarandsonare@google.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
---
 tools/arch/x86/include/uapi/asm/kvm.h         |   1 +
 tools/testing/selftests/kvm/.gitignore        |   1 +
 tools/testing/selftests/kvm/Makefile          |   1 +
 .../testing/selftests/kvm/include/kvm_util.h  |   2 +
 .../selftests/kvm/include/x86_64/processor.h  |  11 +-
 .../selftests/kvm/include/x86_64/vmx.h        |  27 ++
 .../kvm/x86_64/vmx_preemption_timer_test.c    | 255 ++++++++++++++++++
 7 files changed, 294 insertions(+), 4 deletions(-)
 create mode 100644 tools/testing/selftests/kvm/x86_64/vmx_preemption_timer_test.c

diff --git a/tools/arch/x86/include/uapi/asm/kvm.h b/tools/arch/x86/include/uapi/asm/kvm.h
index 3f3f780c8c650..43e24903812c4 100644
--- a/tools/arch/x86/include/uapi/asm/kvm.h
+++ b/tools/arch/x86/include/uapi/asm/kvm.h
@@ -400,6 +400,7 @@ struct kvm_sync_regs {
 struct kvm_vmx_nested_state_data {
 	__u8 vmcs12[KVM_STATE_NESTED_VMX_VMCS_SIZE];
 	__u8 shadow_vmcs12[KVM_STATE_NESTED_VMX_VMCS_SIZE];
+	__u64 preemption_timer_deadline;
 };

 struct kvm_vmx_nested_state_hdr {
diff --git a/tools/testing/selftests/kvm/.gitignore b/tools/testing/selftests/kvm/.gitignore
index 222e50104296a..f159718f90c0a 100644
--- a/tools/testing/selftests/kvm/.gitignore
+++ b/tools/testing/selftests/kvm/.gitignore
@@ -10,6 +10,7 @@
 /x86_64/set_sregs_test
 /x86_64/smm_test
 /x86_64/state_test
+/x86_64/vmx_preemption_timer_test
 /x86_64/svm_vmcall_test
 /x86_64/sync_regs_test
 /x86_64/vmx_close_while_nested_test
diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index c66f4eec34111..780f0c189a7bc 100644
--- a/tools/testing/selftests/kvm/Makefile
+++ b/tools/testing/selftests/kvm/Makefile
@@ -20,6 +20,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/platform_info_test
 TEST_GEN_PROGS_x86_64 += x86_64/set_sregs_test
 TEST_GEN_PROGS_x86_64 += x86_64/smm_test
 TEST_GEN_PROGS_x86_64 += x86_64/state_test
+TEST_GEN_PROGS_x86_64 += x86_64/vmx_preemption_timer_test
 TEST_GEN_PROGS_x86_64 += x86_64/svm_vmcall_test
 TEST_GEN_PROGS_x86_64 += x86_64/sync_regs_test
 TEST_GEN_PROGS_x86_64 += x86_64/vmx_close_while_nested_test
diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index e244c6ecfc1d5..919e161dd2893 100644
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -314,6 +314,8 @@ void ucall_uninit(struct kvm_vm *vm);
 void ucall(uint64_t cmd, int nargs, ...);
 uint64_t get_ucall(struct kvm_vm *vm, uint32_t vcpu_id, struct ucall *uc);

+#define GUEST_SYNC_ARGS(stage, arg1, arg2, arg3, arg4)	\
+				ucall(UCALL_SYNC, 6, "hello", stage, arg1, arg2, arg3, arg4)
 #define GUEST_SYNC(stage)	ucall(UCALL_SYNC, 2, "hello", stage)
 #define GUEST_DONE()		ucall(UCALL_DONE, 0)
 #define __GUEST_ASSERT(_condition, _nargs, _args...) do {	\
diff --git a/tools/testing/selftests/kvm/include/x86_64/processor.h b/tools/testing/selftests/kvm/include/x86_64/processor.h
index 7428513a4c687..7cb19eca6c72d 100644
--- a/tools/testing/selftests/kvm/include/x86_64/processor.h
+++ b/tools/testing/selftests/kvm/include/x86_64/processor.h
@@ -79,13 +79,16 @@ static inline uint64_t get_desc64_base(const struct desc64 *desc)
 static inline uint64_t rdtsc(void)
 {
 	uint32_t eax, edx;
-
+	uint32_t tsc_val;
 	/*
 	 * The lfence is to wait (on Intel CPUs) until all previous
-	 * instructions have been executed.
+	 * instructions have been executed. If software requires RDTSC to be
+	 * executed prior to execution of any subsequent instruction, it can
+	 * execute LFENCE immediately after RDTSC
 	 */
-	__asm__ __volatile__("lfence; rdtsc" : "=a"(eax), "=d"(edx));
-	return ((uint64_t)edx) << 32 | eax;
+	__asm__ __volatile__("lfence; rdtsc; lfence" : "=a"(eax), "=d"(edx));
+	tsc_val = ((uint64_t)edx) << 32 | eax;
+	return tsc_val;
 }

 static inline uint64_t rdtscp(uint32_t *aux)
diff --git a/tools/testing/selftests/kvm/include/x86_64/vmx.h b/tools/testing/selftests/kvm/include/x86_64/vmx.h
index 3d27069b9ed9c..ccff3e6e27048 100644
--- a/tools/testing/selftests/kvm/include/x86_64/vmx.h
+++ b/tools/testing/selftests/kvm/include/x86_64/vmx.h
@@ -575,6 +575,33 @@ struct vmx_pages {
 	void *eptp;
 };

+union vmx_basic {
+	u64 val;
+	struct {
+		u32 revision;
+		u32	size:13,
+			reserved1:3,
+			width:1,
+			dual:1,
+			type:4,
+			insouts:1,
+			ctrl:1,
+			vm_entry_exception_ctrl:1,
+			reserved2:7;
+	};
+};
+
+union vmx_ctrl_msr {
+	u64 val;
+	struct {
+		u32 set, clr;
+	};
+};
+
+union vmx_basic basic;
+union vmx_ctrl_msr ctrl_pin_rev;
+union vmx_ctrl_msr ctrl_exit_rev;
+
 struct vmx_pages *vcpu_alloc_vmx(struct kvm_vm *vm, vm_vaddr_t *p_vmx_gva);
 bool prepare_for_vmx_operation(struct vmx_pages *vmx);
 void prepare_vmcs(struct vmx_pages *vmx, void *guest_rip, void *guest_rsp);
diff --git a/tools/testing/selftests/kvm/x86_64/vmx_preemption_timer_test.c b/tools/testing/selftests/kvm/x86_64/vmx_preemption_timer_test.c
new file mode 100644
index 0000000000000..e2f5dccb4d5ba
--- /dev/null
+++ b/tools/testing/selftests/kvm/x86_64/vmx_preemption_timer_test.c
@@ -0,0 +1,255 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * VMX-preemption timer test
+ *
+ * Copyright (C) 2020, Google, LLC.
+ *
+ * Test to ensure the VM-Enter after migration doesn't
+ * incorrectly restarts the timer with the full timer
+ * value instead of partially decayed timer value
+ *
+ */
+#define _GNU_SOURCE /* for program_invocation_short_name */
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+
+#include "test_util.h"
+
+#include "kvm_util.h"
+#include "processor.h"
+#include "vmx.h"
+
+#define VCPU_ID		5
+#define PREEMPTION_TIMER_VALUE			100000000ull
+#define PREEMPTION_TIMER_VALUE_THRESHOLD1	 80000000ull
+
+u32 vmx_pt_rate;
+bool l2_save_restore_done;
+static u64 l2_vmx_pt_start;
+volatile u64 l2_vmx_pt_finish;
+
+void l2_guest_code(void)
+{
+	u64 vmx_pt_delta;
+
+	vmcall();
+	l2_vmx_pt_start = (rdtsc() >> vmx_pt_rate) << vmx_pt_rate;
+
+	/*
+	 * Wait until the 1st threshold has passed
+	 */
+	do {
+		l2_vmx_pt_finish = rdtsc();
+		vmx_pt_delta = (l2_vmx_pt_finish - l2_vmx_pt_start) >>
+				vmx_pt_rate;
+	} while (vmx_pt_delta < PREEMPTION_TIMER_VALUE_THRESHOLD1);
+
+	/*
+	 * Force L2 through Save and Restore cycle
+	 */
+	GUEST_SYNC(1);
+
+	l2_save_restore_done = 1;
+
+	/*
+	 * Now wait for the preemption timer to fire and
+	 * exit to L1
+	 */
+	while ((l2_vmx_pt_finish = rdtsc()))
+		;
+}
+
+void l1_guest_code(struct vmx_pages *vmx_pages)
+{
+#define L2_GUEST_STACK_SIZE 64
+	unsigned long l2_guest_stack[L2_GUEST_STACK_SIZE];
+	u64 l1_vmx_pt_start;
+	u64 l1_vmx_pt_finish;
+	u64 l1_tsc_deadline, l2_tsc_deadline;
+
+	GUEST_ASSERT(vmx_pages->vmcs_gpa);
+	GUEST_ASSERT(prepare_for_vmx_operation(vmx_pages));
+	GUEST_ASSERT(load_vmcs(vmx_pages));
+	GUEST_ASSERT(vmptrstz() == vmx_pages->vmcs_gpa);
+
+	prepare_vmcs(vmx_pages, l2_guest_code,
+		     &l2_guest_stack[L2_GUEST_STACK_SIZE]);
+
+	/*
+	 * Check for Preemption timer support
+	 */
+	basic.val = rdmsr(MSR_IA32_VMX_BASIC);
+	ctrl_pin_rev.val = rdmsr(basic.ctrl ? MSR_IA32_VMX_TRUE_PINBASED_CTLS
+			: MSR_IA32_VMX_PINBASED_CTLS);
+	ctrl_exit_rev.val = rdmsr(basic.ctrl ? MSR_IA32_VMX_TRUE_EXIT_CTLS
+			: MSR_IA32_VMX_EXIT_CTLS);
+
+	if (!(ctrl_pin_rev.clr & PIN_BASED_VMX_PREEMPTION_TIMER) ||
+	    !(ctrl_exit_rev.clr & VM_EXIT_SAVE_VMX_PREEMPTION_TIMER))
+		return;
+
+	GUEST_ASSERT(!vmlaunch());
+	GUEST_ASSERT(vmreadz(VM_EXIT_REASON) == EXIT_REASON_VMCALL);
+	vmwrite(GUEST_RIP, vmreadz(GUEST_RIP) + vmreadz(VM_EXIT_INSTRUCTION_LEN));
+
+	/*
+	 * Turn on PIN control and resume the guest
+	 */
+	GUEST_ASSERT(!vmwrite(PIN_BASED_VM_EXEC_CONTROL,
+			      vmreadz(PIN_BASED_VM_EXEC_CONTROL) |
+			      PIN_BASED_VMX_PREEMPTION_TIMER));
+
+	GUEST_ASSERT(!vmwrite(VMX_PREEMPTION_TIMER_VALUE,
+			      PREEMPTION_TIMER_VALUE));
+
+	vmx_pt_rate = rdmsr(MSR_IA32_VMX_MISC) & 0x1F;
+
+	l2_save_restore_done = 0;
+
+	l1_vmx_pt_start = (rdtsc() >> vmx_pt_rate) << vmx_pt_rate;
+
+	GUEST_ASSERT(!vmresume());
+
+	l1_vmx_pt_finish = rdtsc();
+
+	/*
+	 * Ensure exit from L2 happens after L2 goes through
+	 * save and restore
+	 */
+	GUEST_ASSERT(l2_save_restore_done);
+
+	/*
+	 * Ensure the exit from L2 is due to preemption timer expiry
+	 */
+	GUEST_ASSERT(vmreadz(VM_EXIT_REASON) == EXIT_REASON_PREEMPTION_TIMER);
+
+	l1_tsc_deadline = l1_vmx_pt_start +
+		(PREEMPTION_TIMER_VALUE << vmx_pt_rate);
+
+	l2_tsc_deadline = l2_vmx_pt_start +
+		(PREEMPTION_TIMER_VALUE << vmx_pt_rate);
+
+	/*
+	 * Sync with the host and pass the l1|l2 pt_expiry_finish times and
+	 * tsc deadlines so that host can verify they are as expected
+	 */
+	GUEST_SYNC_ARGS(2, l1_vmx_pt_finish, l1_tsc_deadline,
+		l2_vmx_pt_finish, l2_tsc_deadline);
+}
+
+void guest_code(struct vmx_pages *vmx_pages)
+{
+	if (vmx_pages)
+		l1_guest_code(vmx_pages);
+
+	GUEST_DONE();
+}
+
+int main(int argc, char *argv[])
+{
+	vm_vaddr_t vmx_pages_gva = 0;
+
+	struct kvm_regs regs1, regs2;
+	struct kvm_vm *vm;
+	struct kvm_run *run;
+	struct kvm_x86_state *state;
+	struct ucall uc;
+	int stage;
+
+	/*
+	 * AMD currently does not implement any VMX features, so for now we
+	 * just early out.
+	 */
+	nested_vmx_check_supported();
+
+	/* Create VM */
+	vm = vm_create_default(VCPU_ID, 0, guest_code);
+	vcpu_set_cpuid(vm, VCPU_ID, kvm_get_supported_cpuid());
+	run = vcpu_state(vm, VCPU_ID);
+
+	vcpu_regs_get(vm, VCPU_ID, &regs1);
+
+	if (kvm_check_cap(KVM_CAP_NESTED_STATE_PREEMPTION_TIMER)) {
+		vcpu_alloc_vmx(vm, &vmx_pages_gva);
+		vcpu_args_set(vm, VCPU_ID, 1, vmx_pages_gva);
+	} else {
+		pr_info("will skip vmx preemption timer checks\n");
+		goto done;
+	}
+
+	for (stage = 1;; stage++) {
+		_vcpu_run(vm, VCPU_ID);
+		TEST_ASSERT(run->exit_reason == KVM_EXIT_IO,
+			    "Stage %d: unexpected exit reason: %u (%s),\n",
+			    stage, run->exit_reason,
+			    exit_reason_str(run->exit_reason));
+
+		switch (get_ucall(vm, VCPU_ID, &uc)) {
+		case UCALL_ABORT:
+			TEST_FAIL("%s at %s:%ld", (const char *)uc.args[0],
+				  __FILE__, uc.args[1]);
+			/* NOT REACHED */
+		case UCALL_SYNC:
+			break;
+		case UCALL_DONE:
+			goto done;
+		default:
+			TEST_FAIL("Unknown ucall %lu", uc.cmd);
+		}
+
+		/* UCALL_SYNC is handled here.  */
+		TEST_ASSERT(!strcmp((const char *)uc.args[0], "hello") &&
+			    uc.args[1] == stage, "Stage %d: Unexpected register values vmexit, got %lx",
+			    stage, (ulong)uc.args[1]);
+		/*
+		 * If this stage 2 then we should verify the vmx pt expiry
+		 * is as expected.
+		 * From L1's perspective verify Preemption timer hasn't
+		 * expired too early.
+		 * From L2's perspective verify Preemption timer hasn't
+		 * expired too late.
+		 */
+		if (stage == 2) {
+
+			pr_info("Stage %d: L1 PT expiry TSC (%lu) , L1 TSC deadline (%lu)\n",
+				stage, uc.args[2], uc.args[3]);
+
+			pr_info("Stage %d: L2 PT expiry TSC (%lu) , L2 TSC deadline (%lu)\n",
+				stage, uc.args[4], uc.args[5]);
+
+			TEST_ASSERT(uc.args[2] >= uc.args[3],
+				"Stage %d: L1 PT expiry TSC (%lu) < L1 TSC deadline (%lu)",
+				stage, uc.args[2], uc.args[3]);
+
+			TEST_ASSERT(uc.args[4] < uc.args[5],
+				"Stage %d: L2 PT expiry TSC (%lu) > L2 TSC deadline (%lu)",
+				stage, uc.args[4], uc.args[5]);
+		}
+
+		state = vcpu_save_state(vm, VCPU_ID);
+		memset(&regs1, 0, sizeof(regs1));
+		vcpu_regs_get(vm, VCPU_ID, &regs1);
+
+		kvm_vm_release(vm);
+
+		/* Restore state in a new VM.  */
+		kvm_vm_restart(vm, O_RDWR);
+		vm_vcpu_add(vm, VCPU_ID);
+		vcpu_set_cpuid(vm, VCPU_ID, kvm_get_supported_cpuid());
+		vcpu_load_state(vm, VCPU_ID, state);
+		run = vcpu_state(vm, VCPU_ID);
+		free(state);
+
+		memset(&regs2, 0, sizeof(regs2));
+		vcpu_regs_get(vm, VCPU_ID, &regs2);
+		TEST_ASSERT(!memcmp(&regs1, &regs2, sizeof(regs2)),
+			    "Unexpected register values after vcpu_load_state; rdi: %lx rsi: %lx",
+			    (ulong) regs2.rdi, (ulong) regs2.rsi);
+	}
+
+done:
+	kvm_vm_free(vm);
+}
--
2.27.0.rc0.183.gde8f92d652-goog

Re: [PATCH 1/2 v4] KVM: nVMX: Fix VMX preemption timer migration

[Paolo Bonzini]

On 22/05/20 06:36, Makarand Sonare wrote:
>    #define KVM_STATE_NESTED_RUN_PENDING		0x00000002
>    #define KVM_STATE_NESTED_EVMCS		0x00000004

> +  /* Available with KVM_CAP_NESTED_STATE_PREEMPTION_TIMER */
> +  #define KVM_STATE_NESTED_PREEMPTION_TIMER	0x00000010

Putting this here is confusing, please rename it to
KVM_STATE_VMX_PREEMPTION_TIMER_DEADLINE and number it 0x1.  Also, I
think the capability is not needed since userspace can expect the flags
to be 0 on older kernels.

Paolo