linux-kernel - Re: [PATCH 1/2] VMware guest detection for x86 and x86-64

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Date:	Wed, 24 Sep 2008 21:54:36 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Greg KH <greg@...ah.com>
CC:	Yan Li <elliot.li.tech@...il.com>, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>, joerg.roedel@....com,
	rjmaomao@...il.com, Yinghai Lu <yhlu.kernel@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>, nancydreaming@...il.com
Subject: Re: [PATCH 1/2] VMware guest detection for x86 and x86-64

Greg KH wrote:
> 
> Well, having a config option like this isn't the way to go as it will be
> forced on for all distros and users anyway.
> 
> A simple cpuid test is the easier way to do this, that's what the
> userspace tools do, if it's really needed in the kernel.  But hopefully,
> such things shouldn't be needed within the kernel as it's not Linux's
> fault that the hypervisor has bugs in it :)
> 
> We wouldn't be wanting to work around bugs in Microsoft's hypervisor,
> would we?
> 

We pretty much have to, just as we have to work around bugs in, say, 
AMD's microcode.  We have avoided it so far, but it's gotten to a 
breaking point, and rather than having ad hoc hacks scattered all over 
the place I want a centralized test site setting a single global variable.

Unfortunately, hypervisor vendors haven't adopted a uniform detection 
scheme (CPUID level 0x40000000 is sometimes mentioned as a 
pseudo-standard, but it's not universal, and not all virtualization 
solutions even can override CPUID.)

	-hpa
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