From: "rkrcmar@redhat.com" <rkrcmar@redhat.com>
To: Yang Zhang <yang.zhang.wz@gmail.com>
Cc: "Wu, Feng" <feng.wu@intel.com>,
"pbonzini@redhat.com" <pbonzini@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>
Subject: Re: [PATCH v3 2/4] KVM: x86: Use vector-hashing to deliver lowest-priority interrupts
Date: Fri, 22 Jan 2016 14:49:12 +0100 [thread overview]
Message-ID: <20160122134911.GC14104@potion.brq.redhat.com> (raw)
In-Reply-To: <56A1A94C.7010703@gmail.com>
2016-01-22 12:00+0800, Yang Zhang:
> On 2016/1/22 1:21, rkrcmar@redhat.com wrote:
>>(I think there isn't a practical difference between *r=-1 and *r=0.)
>
> Currently, if *r == -1, the remote_irr may get set. But it seems wrong. I
Yeah ...
> need to have a double check to see whether it is a bug in current code.
Looking forward to the patch!
Thanks.
>>'ret = true' is the better one. We know that the interrupt is not
>>deliverable [1], so there's no point in trying to deliver with the slow
>>path. We behave similarly when the interrupt targets a single disabled
>>APIC.
>>
>>---
>>1: Well ... it's possible that slowpath would deliver it thanks to
>> different handling of disabled APICs, but it's undefined behavior,
>
> why it is undefined behavior? Besides, why we will keep two different
> handling logic for the fast path and slow path? It looks weird.
It does look very weird ... the slow path would require refactoring,
though, so we save effort without a considerable drawback.
(I would love if it behaved identically, but I don't want to force it on
someone and likely won't do it myself ...)
I consider it undefined because SMD says that an OS musn't configure
this behavior and doesn't say what should happen if the OS does => we
could do anything. (Killing the guest would be great for debugging OS
issues, but ours behavior is fairly conservative.)
next prev parent reply other threads:[~2016-01-22 13:49 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-20 1:42 [PATCH v3 0/4] VT-d posted-interrupts follow ups Feng Wu
2016-01-20 1:42 ` [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the interrupt is not single-destination Feng Wu
2016-01-21 3:05 ` Yang Zhang
2016-01-21 3:14 ` Wu, Feng
2016-01-21 3:34 ` Yang Zhang
2016-01-21 4:42 ` Wu, Feng
2016-01-21 4:54 ` Tian, Kevin
2016-01-21 4:59 ` Yang Zhang
2016-01-21 5:07 ` Wu, Feng
2016-01-21 5:35 ` Yang Zhang
2016-01-21 5:41 ` Wu, Feng
2016-01-21 5:44 ` Yang Zhang
2016-01-21 16:35 ` rkrcmar
2016-01-22 2:03 ` Yang Zhang
2016-01-22 13:31 ` rkrcmar
2016-01-25 1:49 ` Yang Zhang
2016-01-25 13:59 ` rkrcmar
2016-01-26 1:44 ` Yang Zhang
2016-01-26 18:22 ` rkrcmar
2016-01-27 2:07 ` Yang Zhang
2016-01-27 15:05 ` rkrcmar
2016-01-21 16:19 ` Radim Krčmář
2016-01-22 1:49 ` Wu, Feng
2016-01-22 13:05 ` Radim Krcmár
2016-01-25 12:22 ` Paolo Bonzini
2016-01-25 12:26 ` Wu, Feng
2016-01-25 12:38 ` Paolo Bonzini
2016-01-25 12:48 ` Wu, Feng
2016-01-25 14:05 ` Radim Krcmár
2016-01-26 0:57 ` Wu, Feng
2016-01-20 1:42 ` [PATCH v3 2/4] KVM: x86: Use vector-hashing to deliver lowest-priority interrupts Feng Wu
2016-01-21 5:23 ` Yang Zhang
2016-01-21 5:33 ` Wu, Feng
2016-01-21 5:42 ` Yang Zhang
2016-01-21 5:46 ` Wu, Feng
2016-01-21 5:57 ` Yang Zhang
2016-01-21 6:02 ` Wu, Feng
2016-01-21 6:07 ` Yang Zhang
2016-01-21 17:21 ` rkrcmar
2016-01-22 2:01 ` Wu, Feng
2016-01-22 4:00 ` Yang Zhang
2016-01-22 13:49 ` rkrcmar [this message]
2016-01-21 19:49 ` Radim Krčmář
2016-01-22 5:12 ` Wu, Feng
2016-01-22 14:01 ` Radim Krcmár
2016-01-25 12:25 ` Paolo Bonzini
2016-01-25 15:20 ` Radim Krcmár
2016-01-25 16:14 ` Paolo Bonzini
2016-01-26 1:10 ` Wu, Feng
2016-01-20 1:42 ` [PATCH v3 3/4] KVM: x86: Add lowest-priority support for vt-d posted-interrupts Feng Wu
2016-01-21 20:16 ` Radim Krčmář
2016-01-22 5:12 ` Wu, Feng
2016-01-22 14:07 ` Radim Krcmár
2016-01-20 1:42 ` [PATCH v3 4/4] KVM/VMX: Add host irq information in trace event when updating IRTE for posted interrupts Feng Wu
2016-01-21 20:19 ` Radim Krčmář
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