openkylin
/
linux
mirror of https://gitee.com/openkylin/linux.git
9
0
Fork 0
Code Issues Projects Releases Wiki Activity

KVM: x86: fix deadline tsc interrupt injection 

The check in kvm_set_lapic_tscdeadline_msr() was trying to prevent a
situation where we lose a pending deadline timer in a MSR write.
Losing it is fine, because it effectively occurs before the timer fired,
so we should be able to cancel or postpone it.

Another problem comes from interaction with QEMU, or other userspace
that can set deadline MSR without a good reason, when timer is already
pending:  one guest's deadline request results in more than one
interrupt because one is injected immediately on MSR write from
userspace and one through hrtimer later.

The solution is to remove the injection when replacing a pending timer
and to improve the usual QEMU path, we inject without a hrtimer when the
deadline has already passed.

Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Reported-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Radim Krčmář 2014-10-10 19:15:09 +02:00 committed by Paolo Bonzini
parent 5d87db7119
commit 1e0ad70cc1
1 changed files with 4 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
arch/x86/kvm/lapic.c
View File

@ -1132,9 +1132,10 @@ static void start_apic_timer(struct kvm_lapic *apic)
if (likely(tscdeadline > guest_tsc)) {
ns = (tscdeadline - guest_tsc) * 1000000ULL;
do_div(ns, this_tsc_khz);
}
hrtimer_start(&apic->lapic_timer.timer,
ktime_add_ns(now, ns), HRTIMER_MODE_ABS);
hrtimer_start(&apic->lapic_timer.timer,
ktime_add_ns(now, ns), HRTIMER_MODE_ABS);
} else
apic_timer_expired(apic);
local_irq_restore(flags);
}
@ -1391,9 +1392,6 @@ void kvm_set_lapic_tscdeadline_msr(struct kvm_vcpu *vcpu, u64 data)
return;
hrtimer_cancel(&apic->lapic_timer.timer);
/* Inject here so clearing tscdeadline won't override new value */
if (apic_has_pending_timer(vcpu))
kvm_inject_apic_timer_irqs(vcpu);
apic->lapic_timer.tscdeadline = data;
start_apic_timer(apic);
}