linux-stable/arch/x86/kvm/irq.c
David Woodhouse 40da8ccd72 KVM: x86/xen: Add event channel interrupt vector upcall
It turns out that we can't handle event channels *entirely* in userspace
by delivering them as ExtINT, because KVM is a bit picky about when it
accepts ExtINT interrupts from a legacy PIC. The in-kernel local APIC
has to have LVT0 configured in APIC_MODE_EXTINT and unmasked, which
isn't necessarily the case for Xen guests especially on secondary CPUs.

To cope with this, add kvm_xen_get_interrupt() which checks the
evtchn_pending_upcall field in the Xen vcpu_info, and delivers the Xen
upcall vector (configured by KVM_XEN_ATTR_TYPE_UPCALL_VECTOR) if it's
set regardless of LAPIC LVT0 configuration. This gives us the minimum
support we need for completely userspace-based implementation of event
channels.

This does mean that vcpu_enter_guest() needs to check for the
evtchn_pending_upcall flag being set, because it can't rely on someone
having set KVM_REQ_EVENT unless we were to add some way for userspace to
do so manually.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
2021-02-04 14:19:39 +00:00

161 lines
3.6 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* irq.c: API for in kernel interrupt controller
* Copyright (c) 2007, Intel Corporation.
* Copyright 2009 Red Hat, Inc. and/or its affiliates.
*
* Authors:
* Yaozu (Eddie) Dong <Eddie.dong@intel.com>
*/
#include <linux/export.h>
#include <linux/kvm_host.h>
#include "irq.h"
#include "i8254.h"
#include "x86.h"
#include "xen.h"
/*
* check if there are pending timer events
* to be processed.
*/
int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu)
{
if (lapic_in_kernel(vcpu))
return apic_has_pending_timer(vcpu);
return 0;
}
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.
*/
int kvm_cpu_has_extint(struct kvm_vcpu *v)
{
/*
* FIXME: interrupt.injected represents an interrupt whose
* 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_xen_has_interrupt(v))
return 1;
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;
}
/*
* check if there is injectable interrupt:
* when virtual interrupt delivery enabled,
* interrupt from apic will handled by hardware,
* we don't need to check it here.
*/
int kvm_cpu_has_injectable_intr(struct kvm_vcpu *v)
{
if (kvm_cpu_has_extint(v))
return 1;
if (!is_guest_mode(v) && kvm_vcpu_apicv_active(v))
return 0;
return kvm_apic_has_interrupt(v) != -1; /* LAPIC */
}
EXPORT_SYMBOL_GPL(kvm_cpu_has_injectable_intr);
/*
* check if there is pending interrupt without
* intack.
*/
int kvm_cpu_has_interrupt(struct kvm_vcpu *v)
{
if (kvm_cpu_has_extint(v))
return 1;
return kvm_apic_has_interrupt(v) != -1; /* LAPIC */
}
EXPORT_SYMBOL_GPL(kvm_cpu_has_interrupt);
/*
* Read pending interrupt(from non-APIC source)
* vector and intack.
*/
static int kvm_cpu_get_extint(struct kvm_vcpu *v)
{
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 (kvm_xen_has_interrupt(v))
return v->kvm->arch.xen.upcall_vector;
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 */
}
/*
* Read pending interrupt vector and intack.
*/
int kvm_cpu_get_interrupt(struct kvm_vcpu *v)
{
int vector = kvm_cpu_get_extint(v);
if (vector != -1)
return vector; /* PIC */
return kvm_get_apic_interrupt(v); /* APIC */
}
EXPORT_SYMBOL_GPL(kvm_cpu_get_interrupt);
void kvm_inject_pending_timer_irqs(struct kvm_vcpu *vcpu)
{
if (lapic_in_kernel(vcpu))
kvm_inject_apic_timer_irqs(vcpu);
}
EXPORT_SYMBOL_GPL(kvm_inject_pending_timer_irqs);
void __kvm_migrate_timers(struct kvm_vcpu *vcpu)
{
__kvm_migrate_apic_timer(vcpu);
__kvm_migrate_pit_timer(vcpu);
static_call_cond(kvm_x86_migrate_timers)(vcpu);
}
bool kvm_arch_irqfd_allowed(struct kvm *kvm, struct kvm_irqfd *args)
{
bool resample = args->flags & KVM_IRQFD_FLAG_RESAMPLE;
return resample ? irqchip_kernel(kvm) : irqchip_in_kernel(kvm);
}