From: Dave Hansen <dave.hansen@intel.com>
To: Ira Weiny <ira.weiny@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
"Edgecombe, Rick P" <rick.p.edgecombe@intel.com>,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 5/5] x86/pkeys: Standardize on u8 for pkey type
Date: Tue, 15 Mar 2022 09:03:26 -0700 [thread overview]
Message-ID: <5b5ae505-84c7-1a46-832a-68bdfd8fd61c@intel.com> (raw)
In-Reply-To: <YjC2jcn7kJKdHrf3@iweiny-desk3>
On 3/15/22 08:53, Ira Weiny wrote:
> On Mon, Mar 14, 2022 at 04:49:12PM -0700, Dave Hansen wrote:
>> On 3/10/22 16:57, ira.weiny@intel.com wrote:
>>> From: Ira Weiny <ira.weiny@intel.com>
>>>
>>> The number of pkeys supported on x86 and powerpc are much smaller than a
>>> u16 value can hold. It is desirable to standardize on the type for
>>> pkeys. powerpc currently supports the most pkeys at 32. u8 is plenty
>>> large for that.
>>>
>>> Standardize on the pkey types by changing u16 to u8.
>>
>> How widely was this intended to "standardize" things? Looks like it may
>> have missed a few spots.
>
> Sorry I think the commit message is misleading you. The justification of u8 as
> the proper type is that no arch has a need for more than 255 pkeys.
>
> This specific patch was intended to only change x86. Per that goal I don't see
> any other places in x86 which uses u16 after this patch.
>
> $ git grep u16 arch/x86 | grep key
> arch/x86/events/intel/uncore_discovery.c: const u16 *type_id = key;
> arch/x86/include/asm/intel_pconfig.h: u16 keyid;
> arch/x86/include/asm/mmu.h: u16 pkey_allocation_map;
> arch/x86/include/asm/pkeys.h: u16 all_pkeys_mask = ((1U << arch_max_pkey()) - 1);
I was also looking at the generic mm code.
>> Also if we're worried about the type needing to changY or with the wrong
>> type being used, I guess we could just to a pkey_t typedef.
>
> I'm not 'worried' about it. But I do think it makes the code cleaner and more
> self documenting.
Yeah, consistency is good. Do you mind taking a look at how a pkey_t
would look, and also seeing how much core mm code should use it?
next prev parent reply other threads:[~2022-03-15 16:06 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-11 0:57 [PATCH 0/5] Pkey User clean up patches ira.weiny
2022-03-11 0:57 ` [PATCH 1/5] x86/pkeys: Clean up arch_set_user_pkey_access() declaration ira.weiny
2022-03-11 0:57 ` [PATCH 2/5] x86/pkeys: Remove __arch_set_user_pkey_access() declaration ira.weiny
2022-03-11 0:57 ` [PATCH 3/5] powerpc/pkeys: Properly type pkey in init_{i}amr() ira.weiny
2022-03-11 0:57 ` [PATCH 4/5] mm/pkeys: Make pkey unsigned in arch_set_user_pkey_access() ira.weiny
2022-03-11 0:57 ` [PATCH 5/5] x86/pkeys: Standardize on u8 for pkey type ira.weiny
2022-03-14 23:49 ` Dave Hansen
2022-03-15 15:53 ` Ira Weiny
2022-03-15 16:03 ` Dave Hansen [this message]
2022-03-15 16:57 ` Ira Weiny
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=5b5ae505-84c7-1a46-832a-68bdfd8fd61c@intel.com \
--to=dave.hansen@intel.com \
--cc=aneesh.kumar@linux.ibm.com \
--cc=dave.hansen@linux.intel.com \
--cc=ira.weiny@intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=rick.p.edgecombe@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).