From: David Woodhouse <dwmw2@infradead.org>
To: kvm@vger.kernel.org
Cc: Sean Christopherson <seanjc@google.com>,
Paul Durrant <paul@xen.org>, Paolo Bonzini <pbonzini@redhat.com>,
Michal Luczaj <mhal@rbox.co>, David Woodhouse <dwmw@amazon.co.uk>
Subject: [PATCH v2 3/8] KVM: x86/xen: remove WARN_ON_ONCE() with false positives in evtchn delivery
Date: Tue, 27 Feb 2024 11:49:17 +0000 [thread overview]
Message-ID: <20240227115648.3104-4-dwmw2@infradead.org> (raw)
In-Reply-To: <20240227115648.3104-1-dwmw2@infradead.org>
From: David Woodhouse <dwmw@amazon.co.uk>
The kvm_xen_inject_vcpu_vector() function has a comment saying "the fast
version will always work for physical unicast", justifying its use of
kvm_irq_delivery_to_apic_fast() and the WARN_ON_ONCE() when that fails.
In fact that assumption isn't true if X2APIC isn't in use by the guest
and there is (8-bit x)APIC ID aliasing. A single "unicast" destination
APIC ID *may* then be delivered to multiple vCPUs. Remove the warning,
and in fact it might as well just call kvm_irq_delivery_to_apic().
Reported-by: Michal Luczaj <mhal@rbox.co>
Fixes: fde0451be8fb3 ("KVM: x86/xen: Support per-vCPU event channel upcall via local APIC")
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
---
arch/x86/kvm/xen.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 06904696759c..54a4bdb63b17 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -10,7 +10,7 @@
#include "x86.h"
#include "xen.h"
#include "hyperv.h"
-#include "lapic.h"
+#include "irq.h"
#include <linux/eventfd.h>
#include <linux/kvm_host.h>
@@ -571,7 +571,6 @@ void kvm_xen_update_runstate(struct kvm_vcpu *v, int state)
void kvm_xen_inject_vcpu_vector(struct kvm_vcpu *v)
{
struct kvm_lapic_irq irq = { };
- int r;
irq.dest_id = v->vcpu_id;
irq.vector = v->arch.xen.upcall_vector;
@@ -580,8 +579,7 @@ void kvm_xen_inject_vcpu_vector(struct kvm_vcpu *v)
irq.delivery_mode = APIC_DM_FIXED;
irq.level = 1;
- /* The fast version will always work for physical unicast */
- WARN_ON_ONCE(!kvm_irq_delivery_to_apic_fast(v->kvm, NULL, &irq, &r, NULL));
+ kvm_irq_delivery_to_apic(v->kvm, NULL, &irq, NULL);
}
/*
--
2.43.0
next prev parent reply other threads:[~2024-02-27 12:19 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-27 11:49 [PATCH v2 0/8] KVM: x86/xen updates David Woodhouse
2024-02-27 11:49 ` [PATCH v2 1/8] KVM: x86/xen: improve accuracy of Xen timers David Woodhouse
2024-03-04 23:44 ` Sean Christopherson
2024-03-05 9:29 ` Paul Durrant
2024-03-05 21:12 ` Sean Christopherson
2024-03-06 9:48 ` Paul Durrant
2024-03-06 9:57 ` David Woodhouse
2024-02-27 11:49 ` [PATCH v2 2/8] KVM: x86/xen: inject vCPU upcall vector when local APIC is enabled David Woodhouse
2024-02-27 11:49 ` David Woodhouse [this message]
2024-02-27 11:49 ` [PATCH v2 4/8] KVM: pfncache: simplify locking and make more self-contained David Woodhouse
2024-03-05 0:08 ` Sean Christopherson
2024-02-27 11:49 ` [PATCH v2 5/8] KVM: x86/xen: fix recursive deadlock in timer injection David Woodhouse
2024-02-27 11:49 ` [PATCH v2 6/8] KVM: x86/xen: split up kvm_xen_set_evtchn_fast() David Woodhouse
2024-02-27 11:49 ` [PATCH v2 7/8] KVM: x86/xen: avoid blocking in hardirq context in kvm_xen_set_evtchn_fast() David Woodhouse
2024-02-27 14:43 ` Steven Rostedt
2024-02-27 17:00 ` David Woodhouse
2024-02-27 17:18 ` Thomas Gleixner
2024-02-27 17:22 ` David Woodhouse
2024-03-07 9:27 ` David Woodhouse
2024-03-07 10:02 ` David Woodhouse
2024-02-27 17:25 ` Steven Rostedt
2024-02-27 17:28 ` David Woodhouse
2024-03-08 18:10 ` David Woodhouse
2024-02-27 11:49 ` [PATCH v2 8/8] KVM: pfncache: clean up rwlock abuse David Woodhouse
2024-02-29 23:12 ` [PATCH v2 0/8] KVM: x86/xen updates Sean Christopherson
2024-03-05 0:35 ` Sean Christopherson
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