From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [KVM PATCH 1/2] KVM: Directly inject interrupts via irqfd Date: Thu, 22 Oct 2009 17:19:48 +0200 Message-ID: <4AE07814.6020906@redhat.com> References: <20091021143042.14955.22470.stgit@dev.haskins.net> <20091021143453.14955.80578.stgit@dev.haskins.net> <20091021152621.GR29477@redhat.com> <4ADF2A1B.3010205@gmail.com> <20091021153640.GS29477@redhat.com> <4ADF2BDD.40706@gmail.com> <4AE07541.8060903@redhat.com> <4AE076E0.7030100@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Gleb Natapov , Gregory Haskins , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, alacrityvm-devel@lists.sourceforge.net To: Gregory Haskins Return-path: In-Reply-To: <4AE076E0.7030100@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 10/22/2009 05:14 PM, Gregory Haskins wrote: > Yeah, I was thinking about that after I initially responded to Gleb. > > I am thinking something along these lines: > > Provide a function that lets you query a GSI for whether it supports > LOCKLESS or not. Then we can either do one of two things: > > 1) Check for the LOCKLESS attribute at irqfd registration, fail if not > present > This is the most practical path and leads to the smallest code. However it has the deficiency of exposing internal implementation details to userspace. In theory userspace could use msi and edge-triggered pic/ioapic interrupts equally well, it shouldn't have to know that we didn't bother to lockfree ioapic/pic. > 2) Cache the LOCKLESS attribute in the irqfd structure, and either go > direct or defer to a workqueue depending on the flag. > While this leads to larger code, it is more consistent. -- error compiling committee.c: too many arguments to function