[RFC PATCH v2 4/4] KVM: x86: Add support for local interrupt requests from userspace

Steve Rutherford
2015-05-15T02:52:27Z

In order to enable userspace PIC support, the userspace PIC needs to
be able to inject local interrupt requests.

This adds the ioctl KVM_REQUEST_PIC_INJECTION and kvm exit
KVM_EXIT_GET_EXTINT.

The vm ioctl KVM_REQUEST_PIC_INJECTION makes a KVM_REQ_EVENT request
on the BSP, which causes the BSP to exit to userspace to fetch the
vector of the underlying external interrupt, which the BSP then
injects into the guest. This matches the PIC spec, and is necessary to
boot Windows.

Compiles for x86.

Has not undergone incremental testing since previous version.

Signed-off-by: Steve Rutherford <srutherford@google.com>
---
Documentation/virtual/kvm/api.txt | 9 ++++++
arch/x86/include/asm/kvm_host.h | 2 ++
arch/x86/kvm/irq.c | 22 +++++++++++++--
arch/x86/kvm/lapic.c | 7 +++++
arch/x86/kvm/lapic.h | 2 ++
arch/x86/kvm/x86.c | 59 +++++++++++++++++++++++++++++++++++++--
include/uapi/linux/kvm.h | 7 +++++
7 files changed, 103 insertions(+), 5 deletions(-)

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 6ab2a3f7..b5d90cb 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -2979,6 +2979,15 @@ len must be a multiple of sizeof(struct kvm_s390_irq). It must be > 0
and it must not exceed (max_vcpus + 32) * sizeof(struct kvm_s390_irq),
which is the maximum number of possibly pending cpu-local interrupts.

+4.96 KVM_REQUEST_PIC_INJECTION
+
+Capability: KVM_CAP_SPLIT_IRQCHIP
+Type: VM ioctl
+Parameters: none
+Returns: 0 on success, -1 on error.
+
+Informs the kernel that userspace has a pending external interrupt.
+

5. The kvm_run structure
------------------------
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 16a6187..2d5390e 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -542,6 +542,8 @@ struct kvm_vcpu_arch {

u64 eoi_exit_bitmaps[4];
int pending_ioapic_eoi;
+ bool userspace_extint_available;
+ int pending_external_vector;
};

struct kvm_lpage_info {
diff --git a/arch/x86/kvm/irq.c b/arch/x86/kvm/irq.c
index 706e47a..1270b2a 100644
--- a/arch/x86/kvm/irq.c
+++ b/arch/x86/kvm/irq.c
@@ -38,12 +38,25 @@ 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.userspace_extint_available ||
+ 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))
+ u8 accept = kvm_apic_accept_pic_intr(v);
+
+ if (accept && irqchip_split(v->kvm))
+ return pending_userspace_extint(v);
+ else if (accept)
return pic_irqchip(v->kvm)->output; /* PIC */
else
return 0;
@@ -91,7 +104,12 @@ 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) && kvm_cpu_has_extint(v)) {
+ int vector = v->arch.pending_external_vector;
+
+ v->arch.pending_external_vector = -1;
+ return vector;
+ } else if (kvm_cpu_has_extint(v))
return kvm_pic_read_irq(v->kvm); /* PIC */
return -1;
}
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index befd54a..95e0ded 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -2086,3 +2086,10 @@ void kvm_lapic_init(void)
jump_label_rate_limit(&apic_hw_disabled, HZ);
jump_label_rate_limit(&apic_sw_disabled, HZ);
}
+
+void kvm_request_pic_injection(struct kvm_vcpu *vcpu)
+{
+ vcpu->arch.userspace_extint_available = true;
+ kvm_make_request(KVM_REQ_EVENT, vcpu);
+ kvm_vcpu_kick(vcpu);
+}
diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
index 71b150c..7831e4d 100644
--- a/arch/x86/kvm/lapic.h
+++ b/arch/x86/kvm/lapic.h
@@ -63,6 +63,8 @@ int kvm_apic_set_irq(struct kvm_vcpu *vcpu, struct kvm_lapic_irq *irq,
unsigned long *dest_map);
int kvm_apic_local_deliver(struct kvm_lapic *apic, int lvt_type);

+void kvm_request_pic_injection(struct kvm_vcpu *vcpu);
+
bool kvm_irq_delivery_to_apic_fast(struct kvm *kvm, struct kvm_lapic *src,
struct kvm_lapic_irq *irq, int *r, unsigned long *dest_map);

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 405d0d3..1dc2877 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -65,6 +65,8 @@
#include <asm/pvclock.h>
#include <asm/div64.h>

+#define GET_VECTOR_FROM_USERSPACE 1
+
#define MAX_IO_MSRS 256
#define KVM_MAX_MCE_BANKS 32
#define KVM_MCE_CAP_SUPPORTED (MCG_CTL_P | MCG_SER_P)
@@ -4151,6 +4153,30 @@ long kvm_arch_vm_ioctl(struct file *filp,
r = kvm_vm_ioctl_enable_cap(kvm, &cap);
break;
}
+ case KVM_REQUEST_PIC_INJECTION: {
+ int i;
+ struct kvm_vcpu *vcpu;
+ struct kvm_vcpu *bsp_vcpu = NULL;
+
+ mutex_lock(&kvm->lock);
+ r = -EEXIST;
+ if (!irqchip_split(kvm))
+ goto out;
+ kvm_for_each_vcpu(i, vcpu, kvm) {
+ if (kvm_vcpu_is_reset_bsp(vcpu)) {
+ bsp_vcpu = vcpu;
+ continue;
+ }
+ }
+ r = -EINVAL;
+ if (bsp_vcpu == NULL)
+ goto interrupt_unlock;
+ kvm_request_pic_injection(bsp_vcpu);
+ r = 0;
+interrupt_unlock:
+ mutex_unlock(&kvm->lock);
+ break;
+ }

default:
r = kvm_vm_ioctl_assigned_device(kvm, ioctl, arg);
@@ -6128,6 +6154,17 @@ static void update_cr8_intercept(struct kvm_vcpu *vcpu)
kvm_x86_ops->update_cr8_intercept(vcpu, tpr, max_irr);
}

+static int must_fetch_userspace_extint(struct kvm_vcpu *vcpu)
+{
+ if (vcpu->arch.userspace_extint_available &&
+ kvm_apic_accept_pic_intr(vcpu)) {
+ vcpu->arch.userspace_extint_available = false;
+ return true;
+ } else
+ return false;
+
+}
+
static int inject_pending_event(struct kvm_vcpu *vcpu, bool req_int_win)
{
int r;
@@ -6192,7 +6229,12 @@ static int inject_pending_event(struct kvm_vcpu *vcpu, bool req_int_win)
return r;
}
if (kvm_x86_ops->interrupt_allowed(vcpu)) {
- kvm_queue_interrupt(vcpu, kvm_cpu_get_interrupt(vcpu),
+ if (irqchip_split(vcpu->kvm) &&
+ must_fetch_userspace_extint(vcpu)) {
+ return GET_VECTOR_FROM_USERSPACE;
+ }
+ kvm_queue_interrupt(vcpu,
+ kvm_cpu_get_interrupt(vcpu),
false);
kvm_x86_ops->set_irq(vcpu);
}
@@ -6356,13 +6398,19 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
}

if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win) {
+ int event;
kvm_apic_accept_events(vcpu);
if (vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED) {
r = 1;
goto out;
}
-
- if (inject_pending_event(vcpu, req_int_win) != 0)
+ event = inject_pending_event(vcpu, req_int_win);
+ if (event == GET_VECTOR_FROM_USERSPACE) {
+ vcpu->run->exit_reason = KVM_EXIT_GET_EXTINT;
+ kvm_make_request(KVM_REQ_EVENT, vcpu);
+ r = 0;
+ goto out;
+ } else if (event != 0)
req_immediate_exit = true;
/* enable NMI/IRQ window open exits if needed */
else if (vcpu->arch.nmi_pending)
@@ -6679,6 +6727,9 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
if (vcpu->sigset_active)
sigprocmask(SIG_SETMASK, &vcpu->sigset, &sigsaved);

+ if (vcpu->run->exit_reason == KVM_EXIT_GET_EXTINT)
+ vcpu->arch.pending_external_vector = vcpu->run->extint.vector;
+
if (unlikely(vcpu->arch.mp_state == KVM_MP_STATE_UNINITIALIZED)) {
kvm_vcpu_block(vcpu);
kvm_apic_accept_events(vcpu);
@@ -7455,6 +7506,8 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
kvm_async_pf_hash_reset(vcpu);
kvm_pmu_init(vcpu);

+ vcpu->arch.pending_external_vector = -1;
+
return 0;
fail_free_wbinvd_dirty_mask:
free_cpumask_var(vcpu->arch.wbinvd_dirty_mask);
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 826a08d..0cf7ed6 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -184,6 +184,7 @@ struct kvm_s390_skeys {
#define KVM_EXIT_SYSTEM_EVENT 24
#define KVM_EXIT_S390_STSI 25
#define KVM_EXIT_IOAPIC_EOI 26
+#define KVM_EXIT_GET_EXTINT 27

/* For KVM_EXIT_INTERNAL_ERROR */
/* Emulate instruction failed. */
@@ -334,6 +335,10 @@ struct kvm_run {
struct {
__u8 vector;
} eoi;
+ /* KVM_EXIT_GET_EXTINT */
+ struct {
+ __u8 vector;
+ } extint;
/* Fix the size of the union. */
char padding[256];
};
@@ -1206,6 +1211,8 @@ struct kvm_s390_ucas_mapping {
/* Available with KVM_CAP_S390_IRQ_STATE */
#define KVM_S390_SET_IRQ_STATE _IOW(KVMIO, 0xb5, struct kvm_s390_irq_state)
#define KVM_S390_GET_IRQ_STATE _IOW(KVMIO, 0xb6, struct kvm_s390_irq_state)
+/* Available with KVM_CAP_SPLIT_IRQCHIP */
+#define KVM_REQUEST_PIC_INJECTION _IO(KVMIO, 0xb7)

#define KVM_DEV_ASSIGN_ENABLE_IOMMU (1 << 0)
#define KVM_DEV_ASSIGN_PCI_2_3 (1 << 1)
--
2.2.0.rc0.207.ga3a616c