linux-kernel - RE: [PATCH v3 2/4] KVM: x86: Use vector-hashing to deliver lowest-priority interrupts

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Message-ID: <E959C4978C3B6342920538CF579893F00C2C180A@SHSMSX104.ccr.corp.intel.com>
Date:	Fri, 22 Jan 2016 02:01:07 +0000
From:	"Wu, Feng" <feng.wu@...el.com>
To:	"rkrcmar@...hat.com" <rkrcmar@...hat.com>
CC:	Yang Zhang <yang.zhang.wz@...il.com>,
	"pbonzini@...hat.com" <pbonzini@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"Wu, Feng" <feng.wu@...el.com>
Subject: RE: [PATCH v3 2/4] KVM: x86: Use vector-hashing to deliver
 lowest-priority interrupts



> -----Original Message-----
> From: rkrcmar@...hat.com [mailto:rkrcmar@...hat.com]
> Sent: Friday, January 22, 2016 1:21 AM
> To: Wu, Feng <feng.wu@...el.com>
> Cc: Yang Zhang <yang.zhang.wz@...il.com>; pbonzini@...hat.com; linux-
> kernel@...r.kernel.org; kvm@...r.kernel.org
> Subject: Re: [PATCH v3 2/4] KVM: x86: Use vector-hashing to deliver lowest-
> priority interrupts



> > Oh, I didn't notice 'ret' is initialized to true, I thought it was initialized
> > to false like another function, I should add a "ret = false' here. We should
> > failed to inject the interrupt since hardware disabled LAPIC is found.
> 
> '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.

Oh, yes, you are right, Thanks a lot!

Thanks,
Feng

> 
> ---
> 1: Well ... it's possible that slowpath would deliver it thanks to
>    different handling of disabled APICs, but it's undefined behavior,
>    so it doesn't matter matter if we don't try.