From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jeremy Fitzhardinge <jeremy@goop.org>
Subject: Re: [PATCH] Refactor hypercall infrastructure
Date: Fri, 14 Sep 2007 13:53:26 -0700
Message-ID: <46EAF4C6.8090903@goop.org>
References: <11897991353793-git-send-email-aliguori@us.ibm.com>
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Cc: kvm-devel@lists.sourceforge.net, Avi Kivity <avi@qumranet.com>,
	Ingo Molnar <mingo@elte.hu>, Dor Laor <dor.laor@qumranet.com>,
	Rusty Russell <rusty@rustcorp.com.au>,
	linux-kernel@vger.kernel.org
To: Anthony Liguori <aliguori@us.ibm.com>
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Anthony Liguori wrote:
> This patch refactors the current hypercall infrastructure to better support live
> migration and SMP.  It eliminates the hypercall page by trapping the UD
> exception that would occur if you used the wrong hypercall instruction for the
> underlying architecture and replacing it with the right one lazily.
>   

I guess it would be pretty rude/unlikely for these opcodes to get reused
in other implementations...  But couldn't you make the page trap
instead, rather than relying on an instruction fault?

> It also introduces the infrastructure to probe for hypercall available via
> CPUID leaves 0x40000002.  CPUID leaf 0x40000003 should be filled out by
> userspace.
>   

Is this compatible with Xen's (and other's) use of cpuid?  That is,
0x40000000 returns a hypervisor-specific signature in e[bcd]x, and eax
has the max hypervisor leaf.

    J