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KVM: x86: Explicitly check for in-kernel PIC when getting ExtINT

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Explicitly check for an in-kernel PIC when checking for a pending ExtINT
in the PIC.  Effectively swapping the split vs. full irqchip logic will
allow guarding the in-kernel I/O APIC (and PIC) emulation with a Kconfig,
and also makes it more obvious that kvm_pic_read_irq() won't result in a
NULL pointer dereference.

Opportunistically add WARNs in the fallthrough path, mostly to document
that the userspace ExtINT logic is only relevant to split IRQ chips.

Acked-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20250611213557.294358-13-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2025-06-11 14:35:51 -07:00
parent 2c31aa747d
commit cd9140ad83
1 changed files with 16 additions and 9 deletions
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25
arch/x86/kvm/irq.c
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@ -42,6 +42,14 @@ static int pending_userspace_extint(struct kvm_vcpu *v)
return v->arch.pending_external_vector != -1;
}
static int get_userspace_extint(struct kvm_vcpu *vcpu)
{
int vector = vcpu->arch.pending_external_vector;
vcpu->arch.pending_external_vector = -1;
return vector;
}
/*
* check if there is pending interrupt from
* non-APIC source without intack.
@ -68,10 +76,11 @@ int kvm_cpu_has_extint(struct kvm_vcpu *v)
if (!kvm_apic_accept_pic_intr(v))
return 0;
if (irqchip_split(v->kvm))
return pending_userspace_extint(v);
else
if (pic_in_kernel(v->kvm))
return v->kvm->arch.vpic->output;
WARN_ON_ONCE(!irqchip_split(v->kvm));
return pending_userspace_extint(v);
}
/*
@ -127,13 +136,11 @@ int kvm_cpu_get_extint(struct kvm_vcpu *v)
return v->kvm->arch.xen.upcall_vector;
#endif
if (irqchip_split(v->kvm)) {
int vector = v->arch.pending_external_vector;
v->arch.pending_external_vector = -1;
return vector;
} else
if (pic_in_kernel(v->kvm))
return kvm_pic_read_irq(v->kvm); /* PIC */
WARN_ON_ONCE(!irqchip_split(v->kvm));
return get_userspace_extint(v);
}
EXPORT_SYMBOL_GPL(kvm_cpu_get_extint);