From: Sandipan Das <sandipan@linux.ibm.com>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: mpe@ellerman.id.au, paulus@samba.org,
naveen.n.rao@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org,
anton@samba.org, ravi.bangoria@linux.ibm.com
Subject: Re: [PATCH 1/6] powerpc sstep: Add maddhd, maddhdu, maddld instruction emulation
Date: Wed, 5 Sep 2018 17:00:49 +0530 [thread overview]
Message-ID: <99722a4e-fea8-7c74-2cb4-7d5efd2c54fa@linux.ibm.com> (raw)
In-Reply-To: <20180904221223.GR24439@gate.crashing.org>
Hi Segher,
On Wednesday 05 September 2018 03:42 AM, Segher Boessenkool wrote:
> On Mon, Sep 03, 2018 at 08:49:33PM +0530, Sandipan Das wrote:
>> +#ifdef __powerpc64__
>> + case 4:
>> + if (!cpu_has_feature(CPU_FTR_ARCH_300))
>> + return -1;
>> +
>> + switch (instr & 0x3f) {
>> + case 48: /* maddhd */
>> + asm("maddhd %0,%1,%2,%3" : "=r" (op->val) :
>> + "r" (regs->gpr[ra]), "r" (regs->gpr[rb]),
>> + "r" (regs->gpr[rc]));
>> + goto compute_done;
>
> If running maddhd does not work, will running it in kernel mode work?
>
Not sure what you meant here but one of the scenarios that I'm aware of
where this is will be used is if we place a probe at a location having
an maddhd instruction. The kernel would first attempt to emulate its
behaviour, which in this case is done by executing the same instruction
(similar to what is done for mulhd and mulhw) and if that fails, try to
execute the instruction natively.
- Sandipan
next prev parent reply other threads:[~2018-09-05 11:33 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-03 15:19 [PATCH 0/6] powerpc sstep: Extend instruction emulation support Sandipan Das
2018-09-03 15:19 ` [PATCH 1/6] powerpc sstep: Add maddhd, maddhdu, maddld instruction emulation Sandipan Das
2018-09-04 22:12 ` Segher Boessenkool
2018-09-05 11:30 ` Sandipan Das [this message]
2019-02-20 0:51 ` Michael Ellerman
2018-09-03 15:19 ` [PATCH 2/6] powerpc sstep: Add darn " Sandipan Das
2019-02-20 0:50 ` Michael Ellerman
2019-02-20 9:49 ` Sandipan Das
2018-09-03 15:19 ` [PATCH 3/6] powerpc sstep: Add cnttzw, cnttzd " Sandipan Das
2018-09-04 21:12 ` Segher Boessenkool
2018-09-05 6:36 ` Paul Mackerras
2018-09-03 15:19 ` [PATCH 4/6] powerpc sstep: Add extswsli " Sandipan Das
2018-09-03 15:19 ` [PATCH 5/6] powerpc sstep: Add modsw, moduw " Sandipan Das
2018-09-03 15:19 ` [PATCH 6/6] powerpc sstep: Add modsd, modud " Sandipan Das
2018-09-04 21:21 ` Segher Boessenkool
2018-09-05 11:53 ` Sandipan Das
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