Am 25.09.21 um 02:55 schrieb Sean Christopherson:
Factor out the "block" part of kvm_vcpu_halt() so that x86 can emulate
non-halt wait/sleep/block conditions that should not be subjected to
halt-polling.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Reviewed-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
---
include/linux/kvm_host.h | 1 +
virt/kvm/kvm_main.c | 50 ++++++++++++++++++++++++++++------------
2 files changed, 36 insertions(+), 15 deletions(-)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index d2a8be3fb9ba..655c2b24db2d 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -966,6 +966,7 @@ void kvm_sigset_activate(struct kvm_vcpu *vcpu);
void kvm_sigset_deactivate(struct kvm_vcpu *vcpu);
void kvm_vcpu_halt(struct kvm_vcpu *vcpu);
+bool kvm_vcpu_block(struct kvm_vcpu *vcpu);
void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu);
void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu);
bool kvm_vcpu_wake_up(struct kvm_vcpu *vcpu);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 280cf1dca7db..fe34457530c2 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3199,6 +3199,34 @@ static int kvm_vcpu_check_block(struct kvm_vcpu *vcpu)
return ret;
}
+/*
+ * Block the vCPU until the vCPU is runnable, an event arrives, or a signal is
+ * pending. This is mostly used when halting a vCPU, but may also be used
+ * directly for other vCPU non-runnable states, e.g. x86's Wait-For-SIPI.
+ */
+bool kvm_vcpu_block(struct kvm_vcpu *vcpu)
+{
+ bool waited = false;
+
+ kvm_arch_vcpu_blocking(vcpu);
+
+ prepare_to_rcuwait(&vcpu->wait);
+ for (;;) {
+ set_current_state(TASK_INTERRUPTIBLE);
+
+ if (kvm_vcpu_check_block(vcpu) < 0)
+ break;
+
+ waited = true;
+ schedule();
+ }
+ finish_rcuwait(&vcpu->wait);
+
+ kvm_arch_vcpu_unblocking(vcpu);
+
+ return waited;
+}
+
static inline void update_halt_poll_stats(struct kvm_vcpu *vcpu, ktime_t start,
ktime_t end, bool success)
{
@@ -3221,6 +3249,12 @@ static inline void update_halt_poll_stats(struct kvm_vcpu *vcpu, ktime_t start,
}
}
+/*
+ * Emulate a vCPU halt condition, e.g. HLT on x86, WFI on arm, etc... If halt
+ * polling is enabled, busy wait for a short time before blocking to avoid the
+ * expensive block+unblock sequence if a wake event arrives soon after the vCPU
+ * is halted.
+ */
void kvm_vcpu_halt(struct kvm_vcpu *vcpu)
{
bool halt_poll_allowed = !kvm_arch_no_poll(vcpu);
@@ -3245,21 +3279,7 @@ void kvm_vcpu_halt(struct kvm_vcpu *vcpu)
} while (kvm_vcpu_can_poll(cur, stop));
}
- kvm_arch_vcpu_blocking(vcpu);
-
- prepare_to_rcuwait(&vcpu->wait);
- for (;;) {
- set_current_state(TASK_INTERRUPTIBLE);
-
- if (kvm_vcpu_check_block(vcpu) < 0)
- break;
-
- waited = true;
- schedule();
- }
- finish_rcuwait(&vcpu->wait);
-
- kvm_arch_vcpu_unblocking(vcpu);
+ waited = kvm_vcpu_block(vcpu);
cur = ktime_get();
if (waited) {
