From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=39910 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OVk2L-0001is-2r for qemu-devel@nongnu.org; Mon, 05 Jul 2010 07:40:34 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OVk2J-0000vX-T7 for qemu-devel@nongnu.org; Mon, 05 Jul 2010 07:40:32 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33526) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OVk2J-0000vN-Hh for qemu-devel@nongnu.org; Mon, 05 Jul 2010 07:40:31 -0400 Message-ID: <4C31C4A3.4070208@redhat.com> Date: Mon, 05 Jul 2010 14:40:19 +0300 From: Avi Kivity MIME-Version: 1.0 Subject: Re: [Qemu-devel] Re: [Bug 599958] Re: Timedrift problems with Win7: hpet missing time drift fixups References: <20100629211802.16137.10587.malonedeb@soybean.canonical.com> <4C2EECE8.8030305@web.de> <201007042306.57852.paul@codesourcery.com> <4C317E2A.7090101@web.de> <20100705064239.GI4689@redhat.com> <4C31807B.2030401@web.de> <20100705070017.GJ4689@redhat.com> <4C318B74.3040403@web.de> <4C319C30.30308@redhat.com> <4C31A0EC.7020803@web.de> <4C31A477.7010205@redhat.com> <4C31BE6A.70307@siemens.com> In-Reply-To: <4C31BE6A.70307@siemens.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jan Kiszka Cc: Blue Swirl , Paul Brook , Gleb Natapov , qemu-devel@nongnu.org On 07/05/2010 02:13 PM, Jan Kiszka wrote: > > That decoupling between state change and acknowledgment worries me. > Dispatching a source to multiple sinks or sharing a sink between > multiple source is no longer cleanly manageable this way. Just look at > the route of some ISA IRQ on x86: You may get an 'ack' from IOAPIC side > and a 'masked' from the ISA side (or vice versa). And the 'masked' will > arrive earlier. I think it is sufficient to only note masks and take action on acks. > Not really straightforward to handle, is it? > No question. > Moreover, it requires a concrete algorithm that takes advantage from the > 'ack' information bit (that should be the only additional information > you gain) to justify the additional effort. A "might have some > advantages" is not enough IMO. Do we have such an algorithm already? > No. The additional information is that you know which cpu(s) processed the interrupt, and when exactly. I don't know how to translate it to a functional advantage, I just have a feeling that it is possible. It's also architecturally cleaner. Masks and acks are architectural events. Injections are not - there's the edge on the LINT0 or INTI2 pins, generation of an APIC message, receipt of the APIC message, and assertion of the APIC-to-core interrupt interface. I'm not sure how the proposed interface maps to that. -- error compiling committee.c: too many arguments to function