From: Paolo Bonzini <pbonzini@redhat.com>
To: "Wu, Feng" <feng.wu@intel.com>, "Michael S. Tsirkin" <mst@redhat.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"yang.zhang.wz@gmail.com" <yang.zhang.wz@gmail.com>,
"rkrcmar@redhat.com" <rkrcmar@redhat.com>
Subject: Re: [PATCH 2/3] kvm: x86: do not use KVM_REQ_EVENT for APICv interrupt injection
Date: Wed, 28 Sep 2016 14:14:14 +0200 [thread overview]
Message-ID: <f57c3e7b-4048-fb2b-5789-5ca8859a1e12@redhat.com> (raw)
In-Reply-To: <E959C4978C3B6342920538CF579893F0198811F4@SHSMSX104.ccr.corp.intel.com>
On 28/09/2016 14:06, Wu, Feng wrote:
>> Then the
>> > guest is entered with PIR.ON, but the PI interrupt is not pending and
>> > hence the interrupt is never delivered to the guest.
> Why "never", at least, the interrupt should be delivered to the guest in the next
> vm-entry, right? I mean vm-entry -> vm-exit -> _vm-entry_ (interrupts will be
> delivered at this vm-entery).
Sure, but you could in principle have a case where the vmexit never
happens (right now nohz_full CPUs have a 1 Hz timer tick, but that's
just a limitation of isolcpus). When that happens, the interrupt might
never be delivered because it is not recorded in IRR.
Also, if the guest issues an EOI, the pending posted interrupt may be
reordered incorrectly with a lower-priority interrupt already in IRR.
But I'll re-check the wording in the commit message before posting the
non-RFC version.
Paolo
next prev parent reply other threads:[~2016-09-28 12:14 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-27 21:20 [RFC PATCH 0/3] kvm: x86: speedups for APICv Paolo Bonzini
2016-09-27 21:20 ` [PATCH 1/3] kvm: x86: avoid atomic operations on APICv vmentry Paolo Bonzini
2016-09-27 21:20 ` [PATCH 2/3] kvm: x86: do not use KVM_REQ_EVENT for APICv interrupt injection Paolo Bonzini
2016-09-27 23:07 ` Michael S. Tsirkin
2016-09-28 8:21 ` Paolo Bonzini
2016-09-28 11:40 ` Wu, Feng
2016-09-28 11:50 ` Paolo Bonzini
2016-09-28 12:06 ` Wu, Feng
2016-09-28 12:14 ` Paolo Bonzini [this message]
2016-10-14 7:37 ` Yang Zhang
2016-10-14 8:12 ` Paolo Bonzini
2016-09-28 13:46 ` Michael S. Tsirkin
2016-09-28 14:08 ` Paolo Bonzini
2016-09-28 10:04 ` Wu, Feng
2016-09-28 10:16 ` Paolo Bonzini
2016-09-28 11:53 ` Wu, Feng
2016-09-28 11:55 ` Paolo Bonzini
2016-09-28 12:07 ` Wu, Feng
2016-10-14 7:12 ` Yang Zhang
2016-09-27 21:20 ` [PATCH 3/3] KVM: x86: do not scan IRR twice on APICv vmentry Paolo Bonzini
2016-09-28 14:00 ` Michael S. Tsirkin
2016-09-28 14:44 ` Paolo Bonzini
2016-09-29 2:51 ` Wu, Feng
2016-10-14 7:32 ` Yang Zhang
2016-10-14 7:45 ` Paolo Bonzini
2016-09-29 19:55 ` [RFC PATCH 0/3] kvm: x86: speedups for APICv Radim Krčmář
2016-09-29 21:41 ` Paolo Bonzini
2016-09-30 13:23 ` Radim Krčmář
2016-09-30 13:33 ` Radim Krčmář
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