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Re: [Xen-devel] [patch] make hypercall_preempt_check() a little more sen

To: Hollis Blanchard <hollisb@xxxxxxxxxx>
Subject: Re: [Xen-devel] [patch] make hypercall_preempt_check() a little more sensitive
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Fri, 31 Mar 2006 10:33:18 +0100
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On 30 Mar 2006, at 18:17, Hollis Blanchard wrote:

It would be an invasive patch to PowerPC Linux to modify the code that
disables the EE bit and additionally have it modify
vcpu_info->evtchn_upcall_mask, especially when that code is in assembly. Instead, we can have hypercall_preempt_check() also check MSR:EE directly.
IA64 may be able to use this facility as well, so I've CC'ed that list.

This patch fixes a problem where an event occurs, Linux calls back into Xen for e.g. console output, Xen sees that an event is pending and creates a
continuation and returns... loop forever.

I'd rather move event_pending() into asm/event.h and then you can monkey with it as you like. That'll also catch other uses of event_pending() where you probably also want the same extra check. I don't really want a proliferation of extra little functions called arch_xxx.

 -- Keir


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