linux/arch/um/os-Linux
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
..
drivers um: Kill directly reference of netdev->priv 2008-12-04 15:07:33 -08:00
skas um: Save FPU registers between task switches 2011-09-14 18:09:37 -07:00
sys-i386
sys-x86_64
aio.c
elf_aux.c um: disable scan_elf_aux() on x86_64 2011-07-25 20:57:13 -07:00
execvp.c
file.c Deal with missing exports for hostfs 2010-08-09 16:47:25 -04:00
helper.c uml: helper.c warning corrections 2011-07-25 20:57:13 -07:00
irq.c
main.c um: disable scan_elf_aux() on x86_64 2011-07-25 20:57:13 -07:00
Makefile um: disable scan_elf_aux() on x86_64 2011-07-25 20:57:13 -07:00
mem.c uml: free resources 2011-07-25 20:57:13 -07:00
process.c um: fix crash while os_dump_core() 2011-05-25 08:39:42 -07:00
registers.c um: Save FPU registers between task switches 2011-09-14 18:09:37 -07:00
sigio.c
signal.c
start_up.c uml: improve error messages 2009-04-01 08:59:16 -07:00
time.c um: fix global timer issue when using CONFIG_NO_HZ 2010-10-26 16:52:03 -07:00
tls.c
tty.c
uaccess.c
umid.c
user_syms.c um: fix _FORTIFY_SOURCE=2 support for kernel modules 2011-07-25 20:57:12 -07:00
util.c um: add earlyprintk support 2011-05-25 08:39:41 -07:00