| commit | 8b84ad942b534f8faeb34b68f0f7277ea375fed0 | |
| author | Jeremy Fitzhardinge <jeremy@xensource.com> | |
| Wed, 18 Jul 2007 01:37:06 +0000 (17 18:37 -0700) | ||
| committer | Jeremy Fitzhardinge <jeremy@goop.org> | |
| Wed, 18 Jul 2007 15:47:44 +0000 (18 08:47 -0700) | ||
| tree | 911472add5b9068a95a77215a70dac63edf6202e | treesnapshot (tar.gz zip) |
| parent | d66bf8fcf3fce058a1cd164a7c8ee6093fdf039c | commitdiff |
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 <jeremy@xensource.com>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
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 <jeremy@xensource.com>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
| arch/i386/xen/enlighten.c | diffblobblamehistory |