Re: [Xen-devel] Re: how to handle paged hypercall args?

To:	Olaf Hering <olaf@xxxxxxxxx>
Subject:	Re: [Xen-devel] Re: how to handle paged hypercall args?
From:	Keir Fraser <keir@xxxxxxx>
Date:	Thu, 02 Dec 2010 10:30:34 +0000
Cc:	xen-devel@xxxxxxxxxxxxxxxxxxx, Jan Beulich <JBeulich@xxxxxxxxxx>
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On 02/12/2010 10:22, "Keir Fraser" <keir@xxxxxxx> wrote:

> Firstly, the usage of waitqueues is broken. The waitqueue_head should be
> shared with code that pages in, so that vcpus can be *woken* at some point
> after they start waiting. As it is, if a vcpu does sleep on its local
> waitqueue_head, it will never wake. You might start with a single global
> waitqueue_head and wake everyone on it every time a page (or maybe page
> batch) is paged in. More sophisticated might be to hash page numbers into a
> array of waitqueue_heads, to reduce false wakeups.

...Or you might have a per-domain waitqueue_head, and do the wake_up() from
code that adds paged-in entries to the guest physmap. That would seem a
pretty sensible way to proceed, to me.

 -- Keir



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Re: [Xen-devel] Re: how to handle paged hypercall args?