From: Marcelo Tosatti <mtosatti@redhat.com>
To: kvm@vger.kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Radim Krcmar <rkrcmar@redhat.com>,
Alan Jenkins <alan.christopher.jenkins@gmail.com>
Subject: [patch 2/2 V2] KVM: LAPIC: cap __delay at lapic_timer_advance_ns
Date: Mon, 20 Jun 2016 22:33:48 -0300 [thread overview]
Message-ID: <20160621013345.GA27706@amt.cnet> (raw)
In-Reply-To: <20160621012829.699158610@redhat.com>
The host timer which emulates the guest LAPIC TSC deadline
timer has its expiration diminished by lapic_timer_advance_ns
nanoseconds. Therefore if, at wait_lapic_expire, a difference
larger than lapic_timer_advance_ns is encountered, delay at most
lapic_timer_advance_ns.
This fixes a problem where the guest can cause the host
to delay for large amounts of time.
Reported-by: Alan Jenkins <alan.christopher.jenkins@gmail.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
---
v2: s/max/min/ !
Index: kvm/arch/x86/kvm/lapic.c
===================================================================
--- kvm.orig/arch/x86/kvm/lapic.c
+++ kvm/arch/x86/kvm/lapic.c
@@ -1164,7 +1164,8 @@ void wait_lapic_expire(struct kvm_vcpu *
/* __delay is delay_tsc whenever the hardware has TSC, thus always. */
if (guest_tsc < tsc_deadline)
- __delay(tsc_deadline - guest_tsc);
+ __delay(min(tsc_deadline - guest_tsc,
+ nsec_to_cycles(vcpu, lapic_timer_advance_ns)));
}
static void start_apic_timer(struct kvm_lapic *apic)
next prev parent reply other threads:[~2016-06-21 1:34 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-21 1:28 [patch 0/2] fix lapic_timer_advance_ns guest triggerable unlimited delays Marcelo Tosatti
2016-06-21 1:28 ` [patch 1/2] KVM: x86: move nsec_to_cycles from x86.c to x86.h Marcelo Tosatti
2016-06-21 1:28 ` [patch 2/2] KVM: LAPIC: cap __delay at lapic_timer_advance_ns Marcelo Tosatti
2016-06-21 1:33 ` Marcelo Tosatti [this message]
2016-06-21 12:13 ` [patch 2/2 V2] " Alan Jenkins
2016-06-21 7:53 ` [patch 0/2] fix lapic_timer_advance_ns guest triggerable unlimited delays Paolo Bonzini
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