This is a note to let you know that I've just added the patch titled
KVM: lapic: Fixup LDR on load in x2apic
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-lapic-fixup-ldr-on-load-in-x2apic.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 12806ba937382fdfdbad62a399aa2dce65c10fcd Mon Sep 17 00:00:00 2001
From: "Dr. David Alan Gilbert" <dgilbert@xxxxxxxxxx>
Date: Fri, 17 Nov 2017 11:52:50 +0000
Subject: KVM: lapic: Fixup LDR on load in x2apic
From: Dr. David Alan Gilbert <dgilbert@xxxxxxxxxx>
commit 12806ba937382fdfdbad62a399aa2dce65c10fcd upstream.
In x2apic mode the LDR is fixed based on the ID rather
than separately loadable like it was before x2.
When kvm_apic_set_state is called, the base is set, and if
it has the X2APIC_ENABLE flag set then the LDR is calculated;
however that value gets overwritten by the memcpy a few lines
below overwriting it with the value that came from userland.
The symptom is a lack of EOI after loading the state
(e.g. after a QEMU migration) and is due to the EOI bitmap
being wrong due to the incorrect LDR. This was seen with
a Win2016 guest under Qemu with irqchip=split whose USB mouse
didn't work after a VM migration.
This corresponds to RH bug:
https://bugzilla.redhat.com/show_bug.cgi?id=1502591
Reported-by: Yiqian Wei <yiwei@xxxxxxxxxx>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@xxxxxxxxxx>
[Applied fixup from Liran Alon. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kvm/lapic.c | 5 +++++
1 file changed, 5 insertions(+)
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -2034,6 +2034,7 @@ static int kvm_apic_state_fixup(struct k
{
if (apic_x2apic_mode(vcpu->arch.apic)) {
u32 *id = (u32 *)(s->regs + APIC_ID);
+ u32 *ldr = (u32 *)(s->regs + APIC_LDR);
if (vcpu->kvm->arch.x2apic_format) {
if (*id != vcpu->vcpu_id)
@@ -2044,6 +2045,10 @@ static int kvm_apic_state_fixup(struct k
else
*id <<= 24;
}
+
+ /* In x2APIC mode, the LDR is fixed and based on the id */
+ if (set)
+ *ldr = kvm_apic_calc_x2apic_ldr(*id);
}
return 0;
Patches currently in stable-queue which might be from dgilbert@xxxxxxxxxx are
queue-4.9/kvm-lapic-fixup-ldr-on-load-in-x2apic.patch
queue-4.9/kvm-lapic-split-out-x2apic-ldr-calculation.patch