From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keir Fraser Subject: Re: irq_guest_eoi_timer interaction with MSI Date: Thu, 13 Nov 2008 15:06:29 +0000 Message-ID: References: <491C4D90.76E4.0078.0@novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <491C4D90.76E4.0078.0@novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Jan Beulich Cc: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org On 13/11/08 14:53, "Jan Beulich" wrote: > Avoiding the EOI query is certainly a secondary issue. What I was asking > was rather a means for the guest to know whether Xen started that EOI > timer, so that it could indicate to Xen to terminate it and unmask the > respective IRQ. This shouldn't require always using PHYSDEVOP_eoi, and > from an abstract point of view also would belong there, but rather in > unmask_evtchn(). Since it would be an obvious thing that if you unmask > an event channel, you also want the underlying PIRQ unmasked, this > could be a compatible addition to the existing EVTCHNOP_unmask. The > only thing missing is a way for the guest to know when to actually use > the hypercall based unmasking - that's what I wanted to add a vector > for. PHYSDEVOP_eoi and unmask happen at the same time for pirqs. The fact that we only need this new mechanism for pirqs, and that we already have a gated hypercall for pirq eoi (and can gate it further if need be) is an argument for hanging this off PHYSDEVOP_eoi imo. >> We should be delaying LAPIC EOI, just as we do for level-triggered IO-APIC >> IRQs (in that case, because masking RTEs in some cases has stupid side >> effects on some damn stupid chipsets). All that logic exists, just needs >> plumbing in for this particular class of non-maskable MSI. > > Like this you mean? Lightly tested it appears to work (but not tested on a > problem system, yet). Yes, a patch like this would be a good thing. -- Keir