linux-kernel - Re: [PATCH] lguest: disable SYSENTER for guests

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Message-Id: <1184229034.6005.780.camel@localhost.localdomain>
Date:	Thu, 12 Jul 2007 18:30:34 +1000
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Avi Kivity <avi@...ranet.com>
Cc:	lkml - Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	virtualization <virtualization@...ts.linux-foundation.org>
Subject: Re: [PATCH] lguest: disable SYSENTER for guests

On Thu, 2007-07-12 at 10:47 +0300, Avi Kivity wrote:
> Rusty Russell wrote:
>  But what kind of daredevil coder would propose such a thing?)
> 
> Ah, so this is why you want ->next in preempt hooks.  Well, my plan for
> this sort of thing (for kvm has the same issues with the *STAR family of
> msrs) is to add a new hook on switching from kernel to userspace, and
> swap those msrs there.  This allows not only the guest1->guest2 case to
> be optimized, but also guest->kthread->guest, which is a common pattern
> with I/O (and very common with -rt, which runs interrupts in threads).

Adding instructions to the syscall path is not going to make you
popular.  But if you do it, I'll use it 8)

Thanks,
Rusty.


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