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

Wood Scott-B07421
Subject: Re: [PATCH 24/37] KVM: PPC: booke: rework rescheduling checks
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On 02/27/2012 06:33 PM, Alexander Graf wrote:

quoted

On 02/27/2012 05:34 PM, Bhushan Bharat-R65777 wrote:

quoted

quoted

+}
+
+/*
+ * 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 =3D 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.

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So how about this (warning! broken whitespace)?
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=20

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 *vcp=

   *
   * 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 =3D 0;
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@@ -483,7 +483,7 @@ static int kvmppc_prepare_to_enter(struct kvm_vcpu *v=

bool check_signal)
                         continue;
                 }
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-               if (check_signal && signal_pending(current))
+               if (signal_pending(current))
                         r =3D 1;
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                 break;

@@ -507,7 +507,7 @@ int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct k=

*vcpu)
         }
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         local_irq_disable();
-       if (kvmppc_prepare_to_enter(vcpu, true)) {
+       if (kvmppc_prepare_to_enter(vcpu)) {
                 kvm_run->exit_reason =3D KVM_EXIT_INTR;
                 ret =3D -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 =3D KVM_EXIT_INTR;
-               r =3D (-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 =3D KVM_EXIT_INTR;
+                       r =3D (-EINTR << 2) | RESUME_HOST | (r &
RESUME_FLAG_NV);
+                       kvmppc_account_exit(vcpu, SIGNAL_EXITS);
+               }
         }
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+out: