From mboxrd@z Thu Jan  1 00:00:00 1970
From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Subject: Re: [PATCH v3 09/23] xsplice: Add support for bug
	frames. (v4)
Date: Wed, 24 Feb 2016 11:22:18 -0500
Message-ID: <20160224162218.GA25409@char.us.oracle.com>
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Cc: Keir Fraser <keir@xen.org>, Ian Campbell <ian.campbell@citrix.com>, jinsong.liu@alibaba-inc.com, xen-devel@lists.xen.org, mpohlack@amazon.de, ross.lagerwall@citrix.com, Stefano Stabellini <stefano.stabellini@citrix.com>, Jan Beulich <jbeulich@suse.com>, xen-devel@lists.xenproject.org, sasha.levin@citrix.com
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. snip..
> There is a neater way of doing this, which doesn't involve having "if (
> regular ) else if ( xsplice )" logic chains through the code.

s/chains/chain/

There is only one that uses the 'xsplice' name in it:-)

The other two are wrapped with the 'is_patch'.
> 
> Given a
> 
> struct virtual_region
> {
>     struct list_head list;
>     unsigned long start, size;
> 
>     struct bug_frame *foo;
>     struct exception_table_entry *bar;
> };
> 
> The init code can construct one for the base hypervisor, and xsplice can
> add or remove entries from the list.  Then, the trap routines search the
> virtual region list for [start, size) and follow the appropriate pointers.

You are suggesting that on bootup we parse the the __stop_bug_frames_[0-3]
(different on ARM), and create an linked list to contain those.

Then xSplice can call in this API to add their own - and on unload it can
unlink them and free them.

If m understanding is correct - while it is certainly much nicer, it has drawbacks:
 - Increases the code to now handle the linked list and all the code around it
   (And correspondingly we may have now some extra bugs to track).
 - Bigger memory consumption - we now to have to consume memory for this list - even
   for the built-in ones.
 - More code to do for v1 of this patchset.

Can we perhaps we can make this a lesser priority and keep it the existing
if ( .. ) else if (xsplice_find_bug()..) code construct for Xen 4.7?

Thanks.