powerpc/process: Fix altivec SPR not being saved
authorOliver O'Halloran <oohall@gmail.com>
Mon, 7 Mar 2016 22:08:47 +0000 (09:08 +1100)
committerMichael Ellerman <mpe@ellerman.id.au>
Tue, 29 Mar 2016 01:08:08 +0000 (12:08 +1100)
commit01d7c2a2de47890934faba91a71d183795e4348d
tree92b4a3070ef4156cccb042d20144952c4b552497
parent08a5bb2921e490939f78f38fd0d02858bb709942
powerpc/process: Fix altivec SPR not being saved

In save_sprs() in process.c contains the following test:

if (cpu_has_feature(cpu_has_feature(CPU_FTR_ALTIVEC)))
t->vrsave = mfspr(SPRN_VRSAVE);

CPU feature with the mask 0x1 is CPU_FTR_COHERENT_ICACHE so the test
is equivilent to:

if (cpu_has_feature(CPU_FTR_ALTIVEC) &&
cpu_has_feature(CPU_FTR_COHERENT_ICACHE))

On CPUs without support for both (i.e G5) this results in vrsave not
being saved between context switches. The vector register save/restore
code doesn't use VRSAVE to determine which registers to save/restore,
but the value of VRSAVE is used to determine if altivec is being used
in several code paths.

Fixes: 152d523e6307 ("powerpc: Create context switch helpers save_sprs() and restore_sprs()")
Cc: stable@vger.kernel.org
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
arch/powerpc/kernel/process.c