[PATCH] ppc64: Detect altivec via firmware on unknown CPUs

This patch adds detection of the Altivec capability of the CPU via the
firmware in addition to the cpu table.  This allows newer CPUs that aren't
in the table to still have working altivec support in the kernel.

It also fixes a problem where if a CPU isn't recognized as having altivec
features, and takes an altivec unavailable exception due to userland
issuing altivec instructions, the kernel would happily enable it and
context switch the registers ...  but not all of them (it would basically
forget vrsave).  With this patch, the kernel will refuse to enable altivec
when the feature isn't detected for the CPU (SIGILL).

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/ppc64/kernel/head.S b/arch/ppc64/kernel/head.S
index fe05f3fbf9d0..92a744c31ab1 100644
--- a/arch/ppc64/kernel/head.S
+++ b/arch/ppc64/kernel/head.S
@@ -922,7 +922,9 @@ fp_unavailable_common:
 altivec_unavailable_common:
         EXCEPTION_PROLOG_COMMON(0xf20, PACA_EXGEN)
 #ifdef CONFIG_ALTIVEC
+BEGIN_FTR_SECTION
         bne     .load_up_altivec        /* if from user, just load it up */
+END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)
 #endif
         bl      .save_nvgprs
         addi    r3,r1,STACK_FRAME_OVERHEAD