From: Joerg Roedel <joerg.roedel@amd.com>
Date: Fri, 14 Jan 2011 15:45:01 +0000 (+0100)
Subject: KVM: SVM: Make sure KERNEL_GS_BASE is valid when loading gs_index
X-Git-Tag: v2.6.38-rc5~25^2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=893a5ab6ee7d51b231ed45aa844f8088642cb6bf;p=pandora-kernel.git

KVM: SVM: Make sure KERNEL_GS_BASE is valid when loading gs_index

The gs_index loading code uses the swapgs instruction to
switch to the user gs_base temporarily. This is unsave in an
lightweight exit-path in KVM on AMD because the
KERNEL_GS_BASE MSR is switches lazily. An NMI happening in
the critical path of load_gs_index may use the wrong GS_BASE
value then leading to unpredictable behavior, e.g. a
triple-fault.

This patch fixes the issue by making sure that load_gs_index
is called only with a valid KERNEL_GS_BASE value loaded in
KVM.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
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