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

From: Christoph Hellwig
Date: Tue Sep 04 2007 - 18:33:21 EST


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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