From: "Jan Beulich" <JBeulich@suse.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>,
Luwei Kang <luwei.kang@intel.com>
Cc: chao.p.peng@intel.com, yong.y.wang@intel.com, xen-devel@lists.xen.org
Subject: Re: [PATCH] x86/cpuid: AVX-512 Feature Detection
Date: Wed, 29 Jun 2016 08:13:56 -0600 [thread overview]
Message-ID: <5773F3C502000078000F9D4E@prv-mh.provo.novell.com> (raw)
In-Reply-To: <bc17f20a-f4c7-77bd-7c39-f357be1eb0a1@citrix.com>
>>> On 29.06.16 at 13:37, <andrew.cooper3@citrix.com> wrote:
> On 29/06/16 11:03, Jan Beulich wrote:
>>>>> On 29.06.16 at 11:50, <andrew.cooper3@citrix.com> wrote:
>>> On 29/06/16 03:20, Luwei Kang wrote:
>>>> --- a/xen/tools/gen-cpuid.py
>>>> +++ b/xen/tools/gen-cpuid.py
>>>> @@ -235,6 +235,10 @@ def crunch_numbers(state):
>>>> # subsequent instruction groups may only be VEX encoded.
>>>> AVX: [FMA, FMA4, F16C, AVX2, XOP],
>>>>
>>>> + # AVX-512 is an extention of AVX2 and it depends on AVX2 available.
>>>> + AVX2: [AVX512F, AVX512DQ, AVX512IFMA, AVX512PF, AVX512ER, AVX512CD,
>>>> + AVX512BW, AVX512VL, AVX512VBMI],
>>> I think this needs adjusting. AVX512F is the base feature and
>>> indication of extra xstate, while all other AVX512 features (e.g.
>>> AVX512DQ) are explicitly documented not needing to check for AVX512F if
>>> the AVX512DQ bit is present.
>> I think the "not" here is wrong? At least my copy (rev 024) requires
>> all involved feature bits to be checked (see e.g. table 2-2 or the
>> individual instruction pages).
>
> Hmm - yet another inconsistency. Some instructions specify a CPUID
> dependency for just AVX512F (EVEX.NDS.512.66.0F.W1 C2 /r ib VCMPPD k1
> {k2}, zmm2, zmm3/m512/m64bcst{sae}, imm8), some for AVX512F and a second
> feature (EVEX.256.66.0F38.W1 19 /r VBROADCASTSD ymm1 {k1}{z}, xmm2/m64)
> , and some only for the second feature (EVEX.512.66.0F.W0 79 /r
> VCVTPS2UQQ zmm1 {k1}{z}, ymm2/m256/m32bcst{er})
>
> FWIW, I still think the dependency expression is ok in its current form.
Oh, of course - I didn't mean to put that under question.
Jan
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next prev parent reply other threads:[~2016-06-29 14:13 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-29 2:20 [PATCH] x86/cpuid: AVX-512 Feature Detection Luwei Kang
2016-06-29 9:50 ` Andrew Cooper
2016-06-29 9:53 ` Andrew Cooper
2016-06-29 10:03 ` Jan Beulich
2016-06-29 11:37 ` Andrew Cooper
2016-06-29 14:13 ` Jan Beulich [this message]
-- strict thread matches above, loose matches on Subject: below --
2016-06-29 1:57 Luwei Kang
2016-06-29 9:21 ` Jan Beulich
2016-06-28 5:51 Luwei Kang
2016-06-28 7:49 ` Jan Beulich
2016-06-28 8:10 ` Kang, Luwei
2016-06-28 8:46 ` Andrew Cooper
2016-06-28 8:51 ` Kang, Luwei
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