Re: [PATCH 1/2] KVM: x86: handle !lapic_in_kernel case in kvm_cpu_*_extint

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On 11/27/20 12:21 PM, Paolo Bonzini wrote:

Centralize handling of interrupts from the userspace APIC
in kvm_cpu_has_extint and kvm_cpu_get_extint, since
userspace APIC interrupts are handled more or less the
same as ExtINTs are with split irqchip.  This removes
duplicated code from kvm_cpu_has_injectable_intr and
kvm_cpu_has_interrupt, and makes the code more similar
between kvm_cpu_has_{extint,interrupt} on one side
and kvm_cpu_get_{extint,interrupt} on the other.

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
  arch/x86/kvm/irq.c   | 85 ++++++++++++++++++--------------------------
  arch/x86/kvm/lapic.c |  2 +-
  2 files changed, 35 insertions(+), 52 deletions(-)

diff --git a/arch/x86/kvm/irq.c b/arch/x86/kvm/irq.c
index 99d118ffc67d..e2d49a506e7f 100644
--- a/arch/x86/kvm/irq.c
+++ b/arch/x86/kvm/irq.c
@@ -42,15 +42,27 @@ static int pending_userspace_extint(struct kvm_vcpu *v)
   */
  static int kvm_cpu_has_extint(struct kvm_vcpu *v)
  {
-       u8 accept = kvm_apic_accept_pic_intr(v);
+       /*
+        * FIXME: interrupt.injected represents an interrupt that it's
+        * side-effects have already been applied (e.g. bit from IRR
+        * already moved to ISR). Therefore, it is incorrect to rely
+        * on interrupt.injected to know if there is a pending
+        * interrupt in the user-mode LAPIC.
+        * This leads to nVMX/nSVM not be able to distinguish
+        * if it should exit from L2 to L1 on EXTERNAL_INTERRUPT on
+        * pending interrupt or should re-inject an injected
+        * interrupt.
+        */
+       if (!lapic_in_kernel(v))
+               return v->arch.interrupt.injected;

-       if (accept) {
-               if (irqchip_split(v->kvm))
-                       return pending_userspace_extint(v);
-               else
-                       return v->kvm->arch.vpic->output;
-       } else
+       if (!kvm_apic_accept_pic_intr(v))
                 return 0;
+
+       if (irqchip_split(v->kvm))
+               return pending_userspace_extint(v);
+       else
+               return v->kvm->arch.vpic->output;
  }

  /*
@@ -61,20 +73,6 @@ static int kvm_cpu_has_extint(struct kvm_vcpu *v)
   */
  int kvm_cpu_has_injectable_intr(struct kvm_vcpu *v)
  {
-       /*
-        * FIXME: interrupt.injected represents an interrupt that it's
-        * side-effects have already been applied (e.g. bit from IRR
-        * already moved to ISR). Therefore, it is incorrect to rely
-        * on interrupt.injected to know if there is a pending
-        * interrupt in the user-mode LAPIC.
-        * This leads to nVMX/nSVM not be able to distinguish
-        * if it should exit from L2 to L1 on EXTERNAL_INTERRUPT on
-        * pending interrupt or should re-inject an injected
-        * interrupt.
-        */
-       if (!lapic_in_kernel(v))
-               return v->arch.interrupt.injected;
-
         if (kvm_cpu_has_extint(v))
                 return 1;

@@ -91,20 +89,6 @@ EXPORT_SYMBOL_GPL(kvm_cpu_has_injectable_intr);
   */
  int kvm_cpu_has_interrupt(struct kvm_vcpu *v)
  {
-       /*
-        * FIXME: interrupt.injected represents an interrupt that it's
-        * side-effects have already been applied (e.g. bit from IRR
-        * already moved to ISR). Therefore, it is incorrect to rely
-        * on interrupt.injected to know if there is a pending
-        * interrupt in the user-mode LAPIC.
-        * This leads to nVMX/nSVM not be able to distinguish
-        * if it should exit from L2 to L1 on EXTERNAL_INTERRUPT on
-        * pending interrupt or should re-inject an injected
-        * interrupt.
-        */
-       if (!lapic_in_kernel(v))
-               return v->arch.interrupt.injected;
-
         if (kvm_cpu_has_extint(v))
                 return 1;

@@ -118,16 +102,21 @@ EXPORT_SYMBOL_GPL(kvm_cpu_has_interrupt);
   */
  static int kvm_cpu_get_extint(struct kvm_vcpu *v)
  {
-       if (kvm_cpu_has_extint(v)) {
-               if (irqchip_split(v->kvm)) {
-                       int vector = v->arch.pending_external_vector;
-
-                       v->arch.pending_external_vector = -1;
-                       return vector;
-               } else
-                       return kvm_pic_read_irq(v->kvm); /* PIC */
-       } else
+       if (!kvm_cpu_has_extint(v)) {
+               WARN_ON(!lapic_in_kernel(v));
                 return -1;
+       }
+
+       if (!lapic_in_kernel(v))
+               return v->arch.interrupt.nr;
+
+       if (irqchip_split(v->kvm)) {
+               int vector = v->arch.pending_external_vector;
+
+               v->arch.pending_external_vector = -1;
+               return vector;
+       } else
+               return kvm_pic_read_irq(v->kvm); /* PIC */
  }

  /*
@@ -135,13 +124,7 @@ static int kvm_cpu_get_extint(struct kvm_vcpu *v)
   */
  int kvm_cpu_get_interrupt(struct kvm_vcpu *v)
  {
-       int vector;
-
-       if (!lapic_in_kernel(v))
-               return v->arch.interrupt.nr;
-
-       vector = kvm_cpu_get_extint(v);
-
+       int vector = kvm_cpu_get_extint(v);
         if (vector != -1)
                 return vector;                  /* PIC */

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 105e7859d1f2..bb5ff761d5e2 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -2465,7 +2465,7 @@ int kvm_apic_has_interrupt(struct kvm_vcpu *vcpu)
         struct kvm_lapic *apic = vcpu->arch.apic;
         u32 ppr;

-       if (!kvm_apic_hw_enabled(apic))
+       if (!kvm_apic_present(vcpu))
                 return -1;

         __apic_update_ppr(apic, &ppr);
--
2.28.0



Reviewed-by: Filippo Sironi <sironi@xxxxxxxxx>



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