[PATCH v2 1/4] KVM: add spinlock optimization framework

Longpeng(Mike)
2017-08-08T04:05:32Z

If the vcpu(me) exit due to request a usermode spinlock, then
the spinlock-holder may be preempted in usermode or kernmode.

But if the vcpu(me) is in kernmode, then the holder must be
preempted in kernmode, so we should choose a vcpu in kernmode
as the most eligible candidate.

This introduces kvm_arch_vcpu_in_kernel() to decide whether the
vcpu is in kernel-mode when it's preempted or spinlock exit.

Signed-off-by: Longpeng(Mike) <longpeng2@huawei.com>
---
arch/arm/kvm/handle_exit.c | 2 +-
arch/arm64/kvm/handle_exit.c | 2 +-
arch/mips/kvm/mips.c | 6 ++++++
arch/powerpc/kvm/powerpc.c | 6 ++++++
arch/s390/kvm/diag.c | 2 +-
arch/s390/kvm/kvm-s390.c | 6 ++++++
arch/x86/kvm/hyperv.c | 2 +-
arch/x86/kvm/svm.c | 4 +++-
arch/x86/kvm/vmx.c | 2 +-
arch/x86/kvm/x86.c | 6 ++++++
include/linux/kvm_host.h | 3 ++-
virt/kvm/arm/arm.c | 5 +++++
virt/kvm/kvm_main.c | 4 +++-
13 files changed, 42 insertions(+), 8 deletions(-)

diff --git a/arch/arm/kvm/handle_exit.c b/arch/arm/kvm/handle_exit.c
index 54442e3..a7ea5db 100644
--- a/arch/arm/kvm/handle_exit.c
+++ b/arch/arm/kvm/handle_exit.c
@@ -67,7 +67,7 @@ static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run)
if (kvm_vcpu_get_hsr(vcpu) & HSR_WFI_IS_WFE) {
trace_kvm_wfx(*vcpu_pc(vcpu), true);
vcpu->stat.wfe_exit_stat++;
- kvm_vcpu_on_spin(vcpu);
+ kvm_vcpu_on_spin(vcpu, kvm_arch_vcpu_in_kernel(vcpu));
} else {
trace_kvm_wfx(*vcpu_pc(vcpu), false);
vcpu->stat.wfi_exit_stat++;
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 17d8a16..d6c8cb6 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -84,7 +84,7 @@ static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run)
if (kvm_vcpu_get_hsr(vcpu) & ESR_ELx_WFx_ISS_WFE) {
trace_kvm_wfx_arm64(*vcpu_pc(vcpu), true);
vcpu->stat.wfe_exit_stat++;
- kvm_vcpu_on_spin(vcpu);
+ kvm_vcpu_on_spin(vcpu, kvm_arch_vcpu_in_kernel(vcpu));
} else {
trace_kvm_wfx_arm64(*vcpu_pc(vcpu), false);
vcpu->stat.wfi_exit_stat++;
diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index d4b2ad1..70208be 100644
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -98,6 +98,12 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
return !!(vcpu->arch.pending_exceptions);
}

+bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
+{
+ return false;
+}
+EXPORT_SYMBOL_GPL(kvm_arch_vcpu_in_kernel);
+
int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
{
return 1;
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 1a75c0b..6184c45 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -58,6 +58,12 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *v)
return !!(v->arch.pending_exceptions) || kvm_request_pending(v);
}

+bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
+{
+ return false;
+}
+EXPORT_SYMBOL_GPL(kvm_arch_vcpu_in_kernel);
+
int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
{
return 1;
diff --git a/arch/s390/kvm/diag.c b/arch/s390/kvm/diag.c
index ce865bd..4ea8c38 100644
--- a/arch/s390/kvm/diag.c
+++ b/arch/s390/kvm/diag.c
@@ -150,7 +150,7 @@ static int __diag_time_slice_end(struct kvm_vcpu *vcpu)
{
VCPU_EVENT(vcpu, 5, "%s", "diag time slice end");
vcpu->stat.diagnose_44++;
- kvm_vcpu_on_spin(vcpu);
+ kvm_vcpu_on_spin(vcpu, kvm_arch_vcpu_in_kernel(vcpu));
return 0;
}

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index af09d34..0b0c689 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2447,6 +2447,12 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
return kvm_s390_vcpu_has_irq(vcpu, 0);
}

+bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
+{
+ return false;
+}
+EXPORT_SYMBOL_GPL(kvm_arch_vcpu_in_kernel);
+
void kvm_s390_vcpu_block(struct kvm_vcpu *vcpu)
{
atomic_or(PROG_BLOCK_SIE, &vcpu->arch.sie_block->prog20);
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 337b6d2..cd0e6e6 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1268,7 +1268,7 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)

switch (code) {
case HVCALL_NOTIFY_LONG_SPIN_WAIT:
- kvm_vcpu_on_spin(vcpu);
+ kvm_vcpu_on_spin(vcpu, kvm_arch_vcpu_in_kernel(vcpu));
break;
case HVCALL_POST_MESSAGE:
case HVCALL_SIGNAL_EVENT:
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 1107626..e6ed24e 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -3749,7 +3749,9 @@ static int interrupt_window_interception(struct vcpu_svm *svm)

static int pause_interception(struct vcpu_svm *svm)
{
- kvm_vcpu_on_spin(&(svm->vcpu));
+ struct kvm_vcpu *vcpu = &(svm->vcpu);
+
+ kvm_vcpu_on_spin(vcpu, kvm_arch_vcpu_in_kernel(vcpu));
return 1;
}

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 9b21b12..9d6223a 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6761,7 +6761,7 @@ static int handle_pause(struct kvm_vcpu *vcpu)
if (ple_gap)
grow_ple_window(vcpu);

- kvm_vcpu_on_spin(vcpu);
+ kvm_vcpu_on_spin(vcpu, kvm_arch_vcpu_in_kernel(vcpu));
return kvm_skip_emulated_instruction(vcpu);
}

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index d734aa8..4430be6 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8439,6 +8439,12 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
return kvm_vcpu_running(vcpu) || kvm_vcpu_has_events(vcpu);
}

+bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
+{
+ return false;
+}
+EXPORT_SYMBOL_GPL(kvm_arch_vcpu_in_kernel);
+
int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
{
return kvm_vcpu_exiting_guest_mode(vcpu) == IN_GUEST_MODE;
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 21a6fd6..91460aa 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -720,7 +720,7 @@ int kvm_vcpu_write_guest(struct kvm_vcpu *vcpu, gpa_t gpa, const void *data,
bool kvm_vcpu_wake_up(struct kvm_vcpu *vcpu);
void kvm_vcpu_kick(struct kvm_vcpu *vcpu);
int kvm_vcpu_yield_to(struct kvm_vcpu *target);
-void kvm_vcpu_on_spin(struct kvm_vcpu *vcpu);
+void kvm_vcpu_on_spin(struct kvm_vcpu *vcpu, bool me_in_kern);
void kvm_load_guest_fpu(struct kvm_vcpu *vcpu);
void kvm_put_guest_fpu(struct kvm_vcpu *vcpu);

@@ -800,6 +800,7 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
void kvm_arch_hardware_unsetup(void);
void kvm_arch_check_processor_compat(void *rtn);
int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu);
+bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu);
int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu);

#ifndef __KVM_HAVE_ARCH_VM_ALLOC
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index a39a1e1..862f820 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -416,6 +416,11 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *v)
&& !v->arch.power_off && !v->arch.pause);
}

+bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
+{
+ return false;
+}
+
/* Just ensure a guest exit from a particular CPU */
static void exit_vm_noop(void *info)
{
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 15252d7..e7720d2 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2317,7 +2317,7 @@ static bool kvm_vcpu_eligible_for_directed_yield(struct kvm_vcpu *vcpu)
#endif
}

-void kvm_vcpu_on_spin(struct kvm_vcpu *me)
+void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool me_in_kern)
{
struct kvm *kvm = me->kvm;
struct kvm_vcpu *vcpu;
@@ -2348,6 +2348,8 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
continue;
if (swait_active(&vcpu->wq) && !kvm_arch_vcpu_runnable(vcpu))
continue;
+ if (me_in_kern && !kvm_arch_vcpu_in_kernel(vcpu))
+ continue;
if (!kvm_vcpu_eligible_for_directed_yield(vcpu))
continue;

--
1.8.3.1