tree 9bb299eb2b957b47371d09fd33a307882e7b9e7a
parent 0b0abeaf3d30cec03ac6497fe978b8f7edecc5ae
author Joerg Roedel <joerg.roedel@amd.com> 1295019901 +0100
committer Avi Kivity <avi@redhat.com> 1297269096 +0200

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>