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authorSteve Rutherford <srutherford@google.com>2015-07-30 11:27:16 +0200
committerPaolo Bonzini <pbonzini@redhat.com>2015-10-01 15:06:29 +0200
commit1c1a9ce973a7863dd46767226bce2a5f12d48bc6 (patch)
treec7234495a61db9dc9d26956853b7495f8910c581 /arch/x86/kvm/irq.c
parentKVM: x86: Add EOI exit bitmap inference (diff)
downloadlinux-1c1a9ce973a7863dd46767226bce2a5f12d48bc6.tar.xz
linux-1c1a9ce973a7863dd46767226bce2a5f12d48bc6.zip
KVM: x86: Add support for local interrupt requests from userspace
In order to enable userspace PIC support, the userspace PIC needs to be able to inject local interrupts even when the APICs are in the kernel. KVM_INTERRUPT now supports sending local interrupts to an APIC when APICs are in the kernel. The ready_for_interrupt_request flag is now only set when the CPU/APIC will immediately accept and inject an interrupt (i.e. APIC has not masked the PIC). When the PIC wishes to initiate an INTA cycle with, say, CPU0, it kicks CPU0 out of the guest, and renedezvous with CPU0 once it arrives in userspace. When the CPU/APIC unmasks the PIC, a KVM_EXIT_IRQ_WINDOW_OPEN is triggered, so that userspace has a chance to inject a PIC interrupt if it had been pending. Overall, this design can lead to a small number of spurious userspace renedezvous. In particular, whenever the PIC transistions from low to high while it is masked and whenever the PIC becomes unmasked while it is low. Note: this does not buffer more than one local interrupt in the kernel, so the VMM needs to enter the guest in order to complete interrupt injection before injecting an additional interrupt. Compiles for x86. Can pass the KVM Unit Tests. Signed-off-by: Steve Rutherford <srutherford@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/irq.c')
-rw-r--r--arch/x86/kvm/irq.c32
1 files changed, 26 insertions, 6 deletions
diff --git a/arch/x86/kvm/irq.c b/arch/x86/kvm/irq.c
index b653ae202c8e..097060e33bd6 100644
--- a/arch/x86/kvm/irq.c
+++ b/arch/x86/kvm/irq.c
@@ -38,14 +38,27 @@ int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu)
EXPORT_SYMBOL(kvm_cpu_has_pending_timer);
/*
+ * check if there is a pending userspace external interrupt
+ */
+static int pending_userspace_extint(struct kvm_vcpu *v)
+{
+ return v->arch.pending_external_vector != -1;
+}
+
+/*
* check if there is pending interrupt from
* non-APIC source without intack.
*/
static int kvm_cpu_has_extint(struct kvm_vcpu *v)
{
- if (kvm_apic_accept_pic_intr(v))
- return pic_irqchip(v->kvm)->output; /* PIC */
- else
+ u8 accept = kvm_apic_accept_pic_intr(v);
+
+ if (accept) {
+ if (irqchip_split(v->kvm))
+ return pending_userspace_extint(v);
+ else
+ return pic_irqchip(v->kvm)->output;
+ } else
return 0;
}
@@ -91,9 +104,16 @@ EXPORT_SYMBOL_GPL(kvm_cpu_has_interrupt);
*/
static int kvm_cpu_get_extint(struct kvm_vcpu *v)
{
- if (kvm_cpu_has_extint(v))
- return kvm_pic_read_irq(v->kvm); /* PIC */
- return -1;
+ 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
+ return -1;
}
/*