Eric Lee / smarc-fsl-linux-kernel

15 Sep, 2011

1 commit

  • fbfe9c847   um: Save FPU registers between task switches ... Browse Code »

    Some time ago Jeff prepared 42daba316557 ("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
    Signed-off-by: Richard Weinberger
    Reported-by:
    Tested-by:
    Cc: Stanislav Meduna
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    Ingo van Lil
     

23 Oct, 2008

1 commit