On Nov 21, 2007, at 7:09 AM, Geert Uytterhoeven wrote:
> On Tue, 20 Nov 2007, Kumar Gala wrote:
>> On Nov 20, 2007, at 11:54 AM, Scott Wood wrote:
>>> On Mon, Nov 19, 2007 at 09:36:57PM -0600, Kumar Gala wrote:
>>>> isel (Integer Select) is a new user space instruction in the
>>>> PowerISA 2.04 spec. Not all processors implement it so lets
>>>> emulate
>>>> to ensure code built with isel will run everywhere.
>>>
>>> Given that the instruction is meant to be a performance enhancement,
>>> we should probably warn the first few times it's emulated, so the
>>> user
>>> knows they should change their toolchain setup if possible.
>>
>> The same is true of mcrxr, popcntb, and possibly string ld/st.
>>
>> Feel free to submit a patch that warns about their usage.
>
> Something like this?
>
> Probably we also want it for:
>
> - arch/powerpc/kernel/align.c
> o emulate_dcbz()
> o emulate_multiple()
> o emulate_fp_pair()
> o emulate_spe()
>
> - arch/powerpc/kernel/softemu8xx.c
> o Soft_emulate_8xx()
>
> - arch/powerpc/kernel/traps.c
> o SoftwareEmulation()
You missed math_emu.
> - arch/powerpc/kernel/vecemu.c
> o emulate_altivec()
I'm not sure I would concern this one emulation, there isn't much you
can do about the denorm fixup.
How about some per processor counters in sysfs under the processor.
> Question: do we want it for emulate_single_step(), too?
What do you mean, we should could the emulation, the emulate single
step just is for handling if you are doing debug while hitting an
emulated insn.
> So far my Debian userland didn't trigger any of them on the PS3, I
> had to
> write an explicit test ;-)
> ---
> arch/powerpc/kernel/traps.c | 19 +++++++++++++++++--
> 1 files changed, 17 insertions(+), 2 deletions(-)
>
> --- a/arch/powerpc/kernel/traps.c
> +++ b/arch/powerpc/kernel/traps.c
> @@ -707,6 +707,14 @@ static int emulate_popcntb_inst(struct p
> return 0;
> }
>
> +#define WARN_EMULATE(type) \
> + do { \
> + static unsigned int count; \
> + if (count++ < 10) \
> + pr_warning("%s used emulated %s instruction\n", \
> + current->comm, type); \
> + } while (0)
> +
> static int emulate_instruction(struct pt_regs *regs)
> {
> u32 instword;
> @@ -721,31 +729,38 @@ static int emulate_instruction(struct pt
>
> /* Emulate the mfspr rD, PVR. */
> if ((instword & INST_MFSPR_PVR_MASK) == INST_MFSPR_PVR) {
> + WARN_EMULATE("mfpvr");
> rd = (instword >> 21) & 0x1f;
> regs->gpr[rd] = mfspr(SPRN_PVR);
> return 0;
> }
>
> /* Emulating the dcba insn is just a no-op. */
> - if ((instword & INST_DCBA_MASK) == INST_DCBA)
> + if ((instword & INST_DCBA_MASK) == INST_DCBA) {
> + WARN_EMULATE("dcba");
> return 0;
> + }
>
> /* Emulate the mcrxr insn. */
> if ((instword & INST_MCRXR_MASK) == INST_MCRXR) {
> int shift = (instword >> 21) & 0x1c;
> unsigned long msk = 0xf0000000UL >> shift;
>
> + WARN_EMULATE("mcrxr");
> regs->ccr = (regs->ccr & ~msk) | ((regs->xer >> shift) & msk);
> regs->xer &= ~0xf0000000UL;
> return 0;
> }
>
> /* Emulate load/store string insn. */
> - if ((instword & INST_STRING_GEN_MASK) == INST_STRING)
> + if ((instword & INST_STRING_GEN_MASK) == INST_STRING) {
> + WARN_EMULATE("string");
> return emulate_string_inst(regs, instword);
> + }
>
> /* Emulate the popcntb (Population Count Bytes) instruction. */
> if ((instword & INST_POPCNTB_MASK) == INST_POPCNTB) {
> + WARN_EMULATE("popcntb");
> return emulate_popcntb_inst(regs, instword);
> }
>
This looks good as a start.
- k
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