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

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Date:	Thu, 25 Sep 2008 05:56:01 -0700
From:	Greg KH <greg@...ah.com>
To:	"H. Peter Anvin" <hpa@...or.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

On Wed, Sep 24, 2008 at 09:54:36PM -0700, H. Peter Anvin wrote:
> 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.

Ok, fair enough.

> 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.)

Ah, I was hoping they were all doing this, as it seems the most "sane"
manner.  Good luck :)

greg k-h
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