From: Zachary Amsden <zach@vmware.com>
To: Pavel Machek <pavel@ucw.cz>
Cc: Zwane Mwaikambo <zwane@arm.linux.org.uk>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: VMI Interface Proposal Documentation for I386, Part 5
Date: Wed, 15 Mar 2006 17:33:33 -0800 [thread overview]
Message-ID: <4418C06D.4050600@vmware.com> (raw)
In-Reply-To: <20060315234137.GF1919@elf.ucw.cz>
Pavel Machek wrote:
>> from the hypervisor perspective - if the guest enables interrupts, and
>> you have something pending to deliver, for correctness, you have to
>> deliver it, right now. But does the kernel truly require that interrupt
>> deliver immediately - in most cases, no. In particular, on the fast
>>
>
> I'd say PCI hardware can delay interrupts for any arbitrary
> delay... so if driver expects to get them "immediately", I'd say it is
> broken. It should be enough to deliver them "soon enough", like not
> more than 1msec late...
>
I agree. One case we hit that did cause us a bug was local APIC
delivery of self-IPIs. I didn't dig too deep into why Linux was unhappy
without immediate delivery (we deferred delivery here unnecessarily, but
did not stop it). I believe this was in SMP specific code that was
using self-IPIs to regenerate IRQs .
Zach
prev parent reply other threads:[~2006-03-16 1:35 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-03-13 19:56 VMI Interface Proposal Documentation for I386, Part 5 Zachary Amsden
2006-03-14 7:59 ` Zwane Mwaikambo
2006-03-14 8:25 ` Zachary Amsden
2006-03-14 8:47 ` Zwane Mwaikambo
2006-03-14 16:45 ` Zachary Amsden
2006-03-14 17:01 ` Zachary Amsden
2006-03-15 23:41 ` Pavel Machek
2006-03-16 1:33 ` Zachary Amsden [this message]
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