The patch below does not apply to the 4.3-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From db2bdcbbbd32e5500b822d5e74ef8b5bd777e687 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= <rkrcmar@xxxxxxxxxx>
Date: Thu, 8 Oct 2015 20:23:34 +0200
Subject: [PATCH] KVM: x86: fix edge EOI and IOAPIC reconfig race
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KVM uses eoi_exit_bitmap to track vectors that need an action on EOI.
The problem is that IOAPIC can be reconfigured while an interrupt with
old configuration is pending and eoi_exit_bitmap only remembers the
newest configuration; thus EOI from the pending interrupt is not
recognized.
(Reconfiguration is not a problem for level interrupts, because IOAPIC
sends interrupt with the new configuration.)
For an edge interrupt with ACK notifiers, like i8254 timer; things can
happen in this order
1) IOAPIC inject a vector from i8254
2) guest reconfigures that vector's VCPU and therefore eoi_exit_bitmap
on original VCPU gets cleared
3) guest's handler for the vector does EOI
4) KVM's EOI handler doesn't pass that vector to IOAPIC because it is
not in that VCPU's eoi_exit_bitmap
5) i8254 stops working
A simple solution is to set the IOAPIC vector in eoi_exit_bitmap if the
vector is in PIR/IRR/ISR.
This creates an unwanted situation if the vector is reused by a
non-IOAPIC source, but I think it is so rare that we don't want to make
the solution more sophisticated. The simple solution also doesn't work
if we are reconfiguring the vector. (Shouldn't happen in the wild and
I'd rather fix users of ACK notifiers instead of working around that.)
The are no races because ioapic injection and reconfig are locked.
Fixes: b053b2aef25d ("KVM: x86: Add EOI exit bitmap inference")
[Before b053b2aef25d, this bug happened only with APICv.]
Fixes: c7c9c56ca26f ("x86, apicv: add virtual interrupt delivery support")
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Radim Krčmář <rkrcmar@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
diff --git a/arch/x86/kvm/ioapic.c b/arch/x86/kvm/ioapic.c
index 2dcda0f188ba..88d0a92d3f94 100644
--- a/arch/x86/kvm/ioapic.c
+++ b/arch/x86/kvm/ioapic.c
@@ -246,7 +246,9 @@ void kvm_ioapic_scan_entry(struct kvm_vcpu *vcpu, u64 *eoi_exit_bitmap)
kvm_irq_has_notifier(ioapic->kvm, KVM_IRQCHIP_IOAPIC, index) ||
index == RTC_GSI) {
if (kvm_apic_match_dest(vcpu, NULL, 0,
- e->fields.dest_id, e->fields.dest_mode))
+ e->fields.dest_id, e->fields.dest_mode) ||
+ (e->fields.trig_mode == IOAPIC_EDGE_TRIG &&
+ kvm_apic_pending_eoi(vcpu, e->fields.vector)))
__set_bit(e->fields.vector,
(unsigned long *)eoi_exit_bitmap);
}
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e28954d2698a..e33aebbf189e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6201,8 +6201,10 @@ static void vcpu_scan_ioapic(struct kvm_vcpu *vcpu)
if (irqchip_split(vcpu->kvm))
kvm_scan_ioapic_routes(vcpu, vcpu->arch.eoi_exit_bitmap);
- else
+ else {
+ kvm_x86_ops->sync_pir_to_irr(vcpu);
kvm_ioapic_scan_entry(vcpu, vcpu->arch.eoi_exit_bitmap);
+ }
kvm_x86_ops->load_eoi_exitmap(vcpu);
}
--
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