Re: [PATCH 24/37] KVM: PPC: booke: rework rescheduling checks

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On 02/27/2012 06:33 PM, Alexander Graf wrote:
On 02/27/2012 05:34 PM, Bhushan Bharat-R65777 wrote:

+}
+
+/*
+ * Common checks before entering the guest world. Call with interrupts
+ * disabled.
+ *
+ * returns !0 if a signal is pending and check_signal is true  */
+static int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu, bool
+check_signal) {
+    int r = 0;
+
+    WARN_ON_ONCE(!irqs_disabled());
+    while (true) {
+        if (need_resched()) {
+            local_irq_enable();
+            cond_resched();
+            local_irq_disable();
+            continue;
+        }
+
+        if (kvmppc_core_prepare_to_enter(vcpu)) {
kvmppc_prepare_to_enter() is called even on heavyweight_exit. Should not this be called only on lightweight_exit?

Yeah, we don't need to call it when exiting anyways. That's a functional change though, which this patch is trying not to introduce. So we should rather do that as a patch on top.

So how about this (warning! broken whitespace)?


diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index 7a16b56..616aa2d 100644
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c
@@ -464,7 +464,7 @@ int kvmppc_core_prepare_to_enter(struct kvm_vcpu *vcpu)
  *
  * returns !0 if a signal is pending and check_signal is true
  */
-static int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu, bool check_signal)
+static int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
 {
        int r = 0;

@@ -483,7 +483,7 @@ static int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu, bool check_signal)
                        continue;
                }

-               if (check_signal && signal_pending(current))
+               if (signal_pending(current))
                        r = 1;

                break;
@@ -507,7 +507,7 @@ int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
        }

        local_irq_disable();
-       if (kvmppc_prepare_to_enter(vcpu, true)) {
+       if (kvmppc_prepare_to_enter(vcpu)) {
                kvm_run->exit_reason = KVM_EXIT_INTR;
                ret = -EINTR;
                goto out;
@@ -941,13 +941,16 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
         * To avoid clobbering exit_reason, only check for signals if we
         * aren't already exiting to userspace for some other reason.
         */
-       local_irq_disable();
-       if (kvmppc_prepare_to_enter(vcpu, !(r & RESUME_HOST))) {
-               run->exit_reason = KVM_EXIT_INTR;
-               r = (-EINTR << 2) | RESUME_HOST | (r & RESUME_FLAG_NV);
-               kvmppc_account_exit(vcpu, SIGNAL_EXITS);
+       if (!(r & RESUME_HOST)) {
+               local_irq_disable();
+               if (kvmppc_prepare_to_enter(vcpu)) {
+                       run->exit_reason = KVM_EXIT_INTR;
+ r = (-EINTR << 2) | RESUME_HOST | (r & RESUME_FLAG_NV);
+                       kvmppc_account_exit(vcpu, SIGNAL_EXITS);
+               }
        }

+out:
        return r;
 }


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