linux-kernel - Re: [GIT PULL] x86 setup: work around bug in Xen HVM

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Date:	Tue, 4 Sep 2007 23:33:04 +0100
From:	Christoph Hellwig <hch@...radead.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Christian Ehrhardt <lk@...e.de>
Subject: Re: [GIT PULL] x86 setup: work around bug in Xen HVM

On Tue, Sep 04, 2007 at 09:55:45AM -0700, H. Peter Anvin wrote:
>     
>     Apparently XEN does not keep the contents of the 48-bit gdt_48 data
>     structure that is passed to lgdt in the XEN machine state. Instead it
>     appears to save the _address_ of the 48-bit descriptor
>     somewhere. Unfortunately this data happens to reside on the stack and
>     is probably no longer availiable at the time of the actual protected
>     mode jump.
>     
>     This is Xen bug but given that there is a one-line patch to work
>     around this problem, the linux kernel should probably do this.  My fix
>     is to make the gdt_48 description in setup_gdt static (in setup_idt
>     this is already the case). This allows the kernel to boot under
>     Xen HVM again.

> -	struct gdt_ptr gdt;
> +	static struct gdt_ptr gdt;

It might make sense to add your above commit message to the code as a comment.
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