From: Jeremy Fitzhardinge Date: Wed, 18 Jul 2007 01:37:06 +0000 (-0700) Subject: xen: hack to prevent bad segment register reload X-Git-Tag: v2.6.23-rc1~498^2~12 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8b84ad942b534f8faeb34b68f0f7277ea375fed0;p=pandora-kernel.git xen: hack to prevent bad segment register reload The hypervisor saves and restores the segment registers as part of the state is saves while context switching. If, during a context switch, the next process doesn't use the TLS segments, it invalidates the GDT entry, causing the segment register reload to fault. This fault effectively doubles the cost of a context switch. This patch is a band-aid workaround which clears the usermode %gs after it has been saved for the previous process, but before it gets reloaded for the next, and it avoids having the hypervisor attempt to erroneously reload it. Signed-off-by: Jeremy Fitzhardinge Signed-off-by: Chris Wright --- Reading git-diff-tree failed