linux-kernel - Re: please revert commit 53f1b1433da7eac2607a4a0898a221a4485fd732 (rtc: push the BKL down into the driver ioctl method)

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Date:	Fri, 25 Jul 2008 22:52:36 -0400
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jeff Chua <jeff.chua.linux@...il.com>
CC:	Eli Collins <ecollins@...are.com>,
	lkml <linux-kernel@...r.kernel.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: please revert commit 53f1b1433da7eac2607a4a0898a221a4485fd732
 (rtc: push the BKL down into the driver ioctl method)

Jeff Chua wrote:
> On Fri, Jul 25, 2008 at 11:55 PM, H. Peter Anvin <hpa@...or.com> wrote:
>> Jeff Chua wrote:
>>> This commit is breaking vmware-6.0.4. Upon booting linux (guest) on
>>> vmware, the whole vmware environment crashed.
>> Quality hypervisor we have there...
> 
> Well then, lets hope Vmware will do something to fix this and remove
> the init_mm stuff.

Well, let me clarify:

- if userspace crashes the kernel, it is a kernel problem (except for 
abuse of certain specific privileged interfaces, like /dev/mem.)

- if a kernel crashes the hypervisor, it is likewise a hypervisor 
problem, even if it was triggered by a bug in the kernel.

The hypervisor, after all, is supposed to provide isolation.

As far as the kernel is concerned, the hypervisor is hardware.  Now, we 
work around bugs in broken hardware all the time, and *if it is sane*, 
we should do so here too.  However, it is *still* a hypervisor problem, 
and Vmware needs to fix it.

	-hpa

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