From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Jan Beulich <JBeulich@suse.com>, Juergen Gross <jgross@suse.com>
Cc: Sergey Dyasli <sergey.dyasli@citrix.com>,
Xen-devel <xen-devel@lists.xen.org>,
Wei Liu <wei.liu2@citrix.com>,
Roger Pau Monne <roger.pau@citrix.com>
Subject: Re: [PATCH 1/4] libx86: Introduce x86_cpuid_lookup_vendor()
Date: Wed, 27 Mar 2019 15:10:15 +0000 [thread overview]
Message-ID: <7a9f67b7-11de-89c1-db82-2eae0ac8f55a@citrix.com> (raw)
In-Reply-To: <5C9A39B00200007800221F23@prv1-mh.provo.novell.com>
On 26/03/2019 14:39, Jan Beulich wrote:
>>>> On 26.03.19 at 15:23, <jgross@suse.com> wrote:
>> IMO especially in the CPUID case it is desirable to explicitly specify
>> the width of the data. Looking at nodes 0x80000002 and following this
>> should be rather clear (and I even think get_model_name() should be
>> modified to use a pointer to uint32_t instead of unsigned int). Using
>> a type with size >= 4 doesn't fit really well. You want size == 4.
> Why? Fixed width types only introduce unnecessary restrictions
> when wanting to re-use code in other environments. And I don't
> see why CPUID nodes 0x8000000[234] would be any better (or
> worse) as an example here. If anything they tell us that neither
> uint32_t nor unsigned int are right, and it should be char[4] or
> uint8_t[4] instead (depending on whether we want to tie
> ourselves to CHAR_BIT == 8, which clearly is more restrictive
> than sizeof(int) >= 4, but otoh is also less likely to get in the
> way).
The ABI of CPUID really is 2x uint32_t input, 4x uint32_t output.
It is only by current convention that the data is also valid ASCII, and
there is absolutely nothing which prevents a new vendor choosing to put
non-ASCII content in their id string. Given the recent developments
from China, I'm slightly surprised that we haven't seen any UTF-8 (or
UTF-16 for that matter) yet.
~Andrew
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next prev parent reply other threads:[~2019-03-27 15:10 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-21 12:21 [PATCH 0/4] x86/cpuid: Handling of synthetic cpuid_policy fields Andrew Cooper
2019-03-21 12:21 ` [PATCH 1/4] libx86: Introduce x86_cpuid_lookup_vendor() Andrew Cooper
2019-03-26 11:52 ` Jan Beulich
2019-03-26 13:11 ` Andrew Cooper
2019-03-26 14:07 ` Jan Beulich
2019-03-26 14:23 ` Juergen Gross
2019-03-26 14:39 ` Jan Beulich
2019-03-27 15:10 ` Andrew Cooper [this message]
[not found] ` <5C9A39B00200007800221F23@suse.com>
2019-03-26 14:47 ` Juergen Gross
2019-03-26 15:23 ` Jan Beulich
2019-03-21 12:21 ` [PATCH 2/4] x86/cpuid: Drop get_cpu_vendor() completely Andrew Cooper
2019-03-26 12:08 ` Jan Beulich
2019-03-26 16:41 ` Andrew Cooper
2019-03-21 12:21 ` [PATCH 3/4] tools/libxc: Use x86_cpuid_lookup_vendor() rather than opencoding the logic Andrew Cooper
2019-03-26 12:09 ` Jan Beulich
2019-03-21 12:21 ` [PATCH 4/4] libx86: Recalculate synthesised cpuid_policy fields when appropriate Andrew Cooper
2019-03-26 12:20 ` Jan Beulich
2019-03-26 12:34 ` Andrew Cooper
[not found] <1553170866*23812*1*git*send*email*andrew.cooper3@citrix.com>
[not found] ` <1553170866*23812*2*git*send*email*andrew.cooper3@citrix.com>
[not found] ` <5C9A12690200007800221E05@prv1*mh.provo.novell.com>
[not found] ` <c5d1df3d*038d*8c0a*97da*a71f8f3fd009@citrix.com>
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