Re: [Stable-review] [046/127] KVM: VMX: Fix host userspace gsbasecorruption

[Ben Hutchings]

On Tue, 2010-12-07 at 16:43 -0800, Greg KH wrote:
> 2.6.32-stable review patch.  If anyone has any objections, please let us know.
> 
> ------------------
> 
> From: Ben Hutchings <ben@xxxxxxxxxxxxxxx>

This should be credited primarily to Avi.

Ben.

> commit c8770e7ba63bb5dd8fe5f9d251275a8fa717fb78 upstream.
> 
> We now use load_gs_index() to load gs safely; unfortunately this also
> changes MSR_KERNEL_GS_BASE, which we managed separately.  This resulted
> in confusion and breakage running 32-bit host userspace on a 64-bit kernel.
> 
> Fix by
> - saving guest MSR_KERNEL_GS_BASE before we we reload the host's gs
> - doing the host save/load unconditionally, instead of only when in guest
>   long mode
> 
> Things can be cleaned up further, but this is the minmal fix for now.
> 
> Signed-off-by: Avi Kivity <avi@xxxxxxxxxx>
> Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
> [bwh: Backport to 2.6.32]
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
[...]

-- 
Ben Hutchings
Once a job is fouled up, anything done to improve it makes it worse.

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