linux-kernel - Re: 2.6.22 x86_64 : kernel initial decompression hangs on vmware

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Message-ID: <46BB7FCC.4040509@qumranet.com>
Date:	Thu, 09 Aug 2007 23:57:48 +0300
From:	Avi Kivity <avi@...ranet.com>
To:	Zachary Amsden <zach@...are.com>
CC:	Gabriel Barazer <gabriel@...va.fr>, Andi Kleen <ak@...e.de>,
	Jim Mattson <jmattson@...are.com>,
	linux-kernel@...r.kernel.org,
	Virtualization Mailing List <virtualization@...ts.osdl.org>,
	kvm-devel <kvm-devel@...ts.sourceforge.net>
Subject: Re: 2.6.22 x86_64 : kernel initial decompression hangs on vmware

Zachary Amsden wrote:
>
> Since I was just involved in the boot decompressor for another bug, I 
> took a look at this.  2.6.22 switches it to be 64-bit code.  VT is 
> very picky about what state it can run in.  Not using VT on Intel 
> 64-bit hardware cripples performance, running at far below normal 
> speed, and taking minutes to decompress the kernel, which is nearly 
> instantaneous otherwise.
>
> To get back into VT in this case, not only do we need to load FS and 
> GS, we also need to setup an initial LDT and task.  Can you try the 
> attached patch and see that it does the right thing?
>
> I've also cc'd the KVM developers, as the same problem will affect 
> them, and hopefully the same patch will fix it.
>

We haven't seen any issue with the 2.6.22 boot decompressor.  Which of 
the four (fs, gs, ldt, or tr) were proving problematic and why?


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