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authorSean Christopherson <seanjc@google.com>2021-10-08 19:12:07 -0700
committerPaolo Bonzini <pbonzini@redhat.com>2021-12-08 04:24:51 -0500
commitfac4268894394213127e43856f41d10f29131e69 (patch)
tree27e741d4283ea10e9b6d131cc753be9e0ee491a3 /virt/kvm
parent91b99ea7065786d0bff1c9281b002455dbaeb08b (diff)
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KVM: Split out a kvm_vcpu_block() helper from kvm_vcpu_halt()
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. Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com> Reviewed-by: David Matlack <dmatlack@google.com> Signed-off-by: Sean Christopherson <seanjc@google.com> Message-Id: <20211009021236.4122790-15-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'virt/kvm')
-rw-r--r--virt/kvm/kvm_main.c52
1 files changed, 36 insertions, 16 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 0d301c95fa1a..370b95ad5f03 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3272,6 +3272,35 @@ out:
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)
+{
+ struct rcuwait *wait = kvm_arch_vcpu_get_wait(vcpu);
+ bool waited = false;
+
+ kvm_arch_vcpu_blocking(vcpu);
+
+ prepare_to_rcuwait(wait);
+ for (;;) {
+ set_current_state(TASK_INTERRUPTIBLE);
+
+ if (kvm_vcpu_check_block(vcpu) < 0)
+ break;
+
+ waited = true;
+ schedule();
+ }
+ finish_rcuwait(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)
{
@@ -3294,9 +3323,14 @@ 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)
{
- struct rcuwait *wait = kvm_arch_vcpu_get_wait(vcpu);
bool halt_poll_allowed = !kvm_arch_no_poll(vcpu);
bool do_halt_poll = halt_poll_allowed && vcpu->halt_poll_ns;
ktime_t start, cur, poll_end;
@@ -3319,21 +3353,7 @@ void kvm_vcpu_halt(struct kvm_vcpu *vcpu)
} while (kvm_vcpu_can_poll(cur, stop));
}
- kvm_arch_vcpu_blocking(vcpu);
-
- prepare_to_rcuwait(wait);
- for (;;) {
- set_current_state(TASK_INTERRUPTIBLE);
-
- if (kvm_vcpu_check_block(vcpu) < 0)
- break;
-
- waited = true;
- schedule();
- }
- finish_rcuwait(wait);
-
- kvm_arch_vcpu_unblocking(vcpu);
+ waited = kvm_vcpu_block(vcpu);
cur = ktime_get();
if (waited) {