kvm/ppc: IRQ disabling cleanup

Simplify the handling of lazy EE by going directly from fully-enabled
to hard-disabled.  This replaces the lazy_irq_pending() check
(including its misplaced kvm_guest_exit() call).

As suggested by Tiejun Chen, move the interrupt disabling into
kvmppc_prepare_to_enter() rather than have each caller do it.  Also
move the IRQ enabling on heavyweight exit into
kvmppc_prepare_to_enter().

Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Alexander Graf <agraf@suse.de>

4 files changed, 26 insertions, 32 deletions

diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h
index 629277df4798..fcd53f0d34ba 100644
--- a/arch/powerpc/include/asm/kvm_ppc.h
+++ b/arch/powerpc/include/asm/kvm_ppc.h
@@ -456,6 +456,12 @@ static inline void kvmppc_fix_ee_before_entry(void)
         trace_hardirqs_on();
 
 #ifdef CONFIG_PPC64
+        /*
+         * To avoid races, the caller must have gone directly from having
+         * interrupts fully-enabled to hard-disabled.
+         */
+        WARN_ON(local_paca->irq_happened != PACA_IRQ_HARD_DIS);
+
         /* Only need to enable IRQs by hard enabling them after this */
         local_paca->irq_happened = 0;
         local_paca->soft_enabled = 1;
diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
index aedba681bb94..e82fafdaf880 100644
--- a/arch/powerpc/kvm/book3s_pr.c
+++ b/arch/powerpc/kvm/book3s_pr.c
@@ -999,14 +999,14 @@ program_interrupt:
                  * and if we really did time things so badly, then we just exit
                  * again due to a host external interrupt.
                  */
-                local_irq_disable();
                 s = kvmppc_prepare_to_enter(vcpu);
-                if (s <= 0) {
-                        local_irq_enable();
+                if (s <= 0)
                         r = s;
-                } else {
+                else {
+                        /* interrupts now hard-disabled */
                         kvmppc_fix_ee_before_entry();
                 }
+
                 kvmppc_handle_lost_ext(vcpu);
         }
 
@@ -1219,12 +1219,10 @@ static int kvmppc_vcpu_run_pr(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
          * really did time things so badly, then we just exit again due to
          * a host external interrupt.
          */
-        local_irq_disable();
         ret = kvmppc_prepare_to_enter(vcpu);
-        if (ret <= 0) {
-                local_irq_enable();
+        if (ret <= 0)
                 goto out;
-        }
+        /* interrupts now hard-disabled */
 
         /* Save FPU state in thread_struct */
         if (current->thread.regs->msr & MSR_FP)
diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index 6a8c32ec4173..07b89c711898 100644
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c
@@ -643,7 +643,7 @@ int kvmppc_core_prepare_to_enter(struct kvm_vcpu *vcpu)
                 local_irq_enable();
                 kvm_vcpu_block(vcpu);
                 clear_bit(KVM_REQ_UNHALT, &vcpu->requests);
-                local_irq_disable();
+                hard_irq_disable();
 
                 kvmppc_set_exit_type(vcpu, EMULATED_MTMSRWE_EXITS);
                 r = 1;
@@ -688,13 +688,12 @@ int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
                 return -EINVAL;
         }
 
-        local_irq_disable();
         s = kvmppc_prepare_to_enter(vcpu);
         if (s <= 0) {
-                local_irq_enable();
                 ret = s;
                 goto out;
         }
+        /* interrupts now hard-disabled */
 
 #ifdef CONFIG_PPC_FPU
         /* Save userspace FPU state in stack */
@@ -1187,12 +1186,11 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
          * aren't already exiting to userspace for some other reason.
          */
         if (!(r & RESUME_HOST)) {
-                local_irq_disable();
                 s = kvmppc_prepare_to_enter(vcpu);
-                if (s <= 0) {
-                        local_irq_enable();
+                if (s <= 0)
                         r = (s << 2) | RESUME_HOST | (r & RESUME_FLAG_NV);
-                } else {
+                else {
+                        /* interrupts now hard-disabled */
                         kvmppc_fix_ee_before_entry();
                 }
         }
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 026dfaaa4772..3cf541a53e2a 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -68,14 +68,16 @@ int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
  */
 int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
 {
-        int r = 1;
+        int r;
+
+        WARN_ON(irqs_disabled());
+        hard_irq_disable();
 
-        WARN_ON_ONCE(!irqs_disabled());
         while (true) {
                 if (need_resched()) {
                         local_irq_enable();
                         cond_resched();
-                        local_irq_disable();
+                        hard_irq_disable();
                         continue;
                 }
 
@@ -101,7 +103,7 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
                         local_irq_enable();
                         trace_kvm_check_requests(vcpu);
                         r = kvmppc_core_check_requests(vcpu);
-                        local_irq_disable();
+                        hard_irq_disable();
                         if (r > 0)
                                 continue;
                         break;
@@ -113,22 +115,12 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
                         continue;
                 }
 
-#ifdef CONFIG_PPC64
-                /* lazy EE magic */
-                hard_irq_disable();
-                if (lazy_irq_pending()) {
-                        /* Got an interrupt in between, try again */
-                        local_irq_enable();
-                        local_irq_disable();
-                        kvm_guest_exit();
-                        continue;
-                }
-#endif
-
                 kvm_guest_enter();
-                break;
+                return 1;
         }
 
+        /* return to host */
+        local_irq_enable();
         return r;
 }
 EXPORT_SYMBOL_GPL(kvmppc_prepare_to_enter);