[PATCH] arm64: mm: support instruction SETEND
leo.yan at linaro.org
Wed Jan 7 02:58:24 PST 2015
On Wed, Jan 07, 2015 at 10:10:34AM +0000, Suzuki K. Poulose wrote:
> On 07/01/15 05:52, Leo Yan wrote:
> >Currently kernel has set the bit SCTLR_EL1.SED, so the SETEND
> >instruction will be treated as UNALLOCATED; this error can be
> >reproduced when ARMv8 cpu runs with EL1/aarch64 and EL0/aarch32
> >mode, finally kernel will trap the exception if the userspace
> >libs use SETEND instruction.
> >So this patch clears bit SCTLR_EL1.SED to support SETEND instruction.
> The best way to do this, is via the instruction emulation framework
> added by Punit, which handles the armv8 deprecated/obsoleted
> instructions. This is now queued for 3.19.
> I have a patchset which adds the 'SETEND' emulation support to the
> framework. This will enable better handling of the feature,
> including finding out the users of the deprecated instruction (when
> we switch to the emulation mode).
i'm a little confuse for this point:
if the deprecated instructions cannot be supported by CPU, then only
can use emulation; on the other hand, if CPU can natively support the
deprecated instruction, why we cannot directly enable this h/w feature?
if use the emulation mode, suppose here will have performance penalty.
how about u think for this? :-)
> >Signed-off-by: Leo Yan <leo.yan at linaro.org>
> >Signed-off-by: Xiaolong Ye <yexl at marvell.com>
> > arch/arm64/mm/proc.S | 6 +++---
> > 1 file changed, 3 insertions(+), 3 deletions(-)
> >diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
> >index 4e778b1..66a7363 100644
> >--- a/arch/arm64/mm/proc.S
> >+++ b/arch/arm64/mm/proc.S
> >@@ -249,9 +249,9 @@ ENDPROC(__cpu_setup)
> > * CE0 XWHW CZ ME TEEA S
> > * .... .IEE .... NEAI TE.I ..AD DEN0 ACAM
> > * 0011 0... 1101 ..0. ..0. 10.. .... .... < hardware reserved
> >- * .... .1.. .... 01.1 11.1 ..01 0001 1101 < software settings
> >+ * .... .1.. .... 01.1 11.1 ..00 0001 1101 < software settings
> > */
> > .type crval, #object
> > crval:
> >- .word 0x000802e2 // clear
> >- .word 0x0405d11d // set
> >+ .word 0x000803e2 // clear
> >+ .word 0x0405d01d // set
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