Ingo van Lil fbfe9c847e um: Save FPU registers between task switches ... Some time ago Jeff prepared 42daba3165 ("uml: stop saving process FP state") for UML to stop saving the process FP state between task switches. The assumption was that since with SKAS0 every guest process runs inside a host process context the host OS will take care of keeping the proper FP state. Unfortunately this is not true for multi-threaded applications, where all guest threads share a single host process context yet all may use the FPU on their own. Although I haven't verified it I suspect things to be even worse in SKAS3 mode where all guest processes run inside a single host process. The patch reintroduces the saving and restoring of the FP context between task switches. [richard@nod.at: Ingo posted this patch in 2009, sadly it was never applied and got lost. Now in 2011 the problem was reported by Gunnar.] Signed-off-by: Ingo van Lil <inguin@gmx.de> Signed-off-by: Richard Weinberger <richard@nod.at> Reported-by: <gunnarlindroth@hotmail.com> Tested-by: <gunnarlindroth@hotmail.com> Cc: Stanislav Meduna <stano@meduna.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2011-09-14 18:09:37 -07:00
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sysdep	um: Save FPU registers between task switches	2011-09-14 18:09:37 -07:00