From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andi Kleen <andi@firstfloor.org>
Subject: Re: Cross vendor migration ideas
Date: Wed, 12 Nov 2008 21:06:48 +0100
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	<491AFA36.4040909@codemonkey.ws>
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Cc: Alexander Graf <agraf@suse.de>,
	"kvm@vger.kernel.org list" <kvm@vger.kernel.org>,
	Amit Shah <amit.shah@redhat.com>, Avi Kivity <avi@redhat.com>,
	Elsie Wahlig <elsie.wahlig@amd.com>,
	"Serebrin, Benjamin (Calendar)" <Benjamin.Serebrin@exchange.amd.com>,
	"Nakajima, Jun" <jun.nakajima@intel.com>
To: Anthony Liguori <anthony@codemonkey.ws>
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In-Reply-To: <491AFA36.4040909@codemonkey.ws> (Anthony Liguori's message of "Wed, 12 Nov 2008 09:45:58 -0600")
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Anthony Liguori <anthony@codemonkey.ws> writes:
>
> I wonder if patching is an option?

Not by patching instructions because SYSENTER and SYSCALL have
completely different semantics (e.g. regarding register use). That is
why the entry paths are different on both sides.

In theory you could switch the entry paths around, but that would
be highly kernel version specific.

One easy way is to just clear the SEP and SYSCALL32 flags
in CPUID, then int 0x80 will be always used. Of course it'll
cost you in performance significantly. I wouldn't recommend
to make it default.

-Andi

-- 
ak@linux.intel.com