Messages in this thread | | | Date | Tue, 15 Mar 2022 09:03:26 -0700 | From | Dave Hansen <> | Subject | Re: [PATCH 5/5] x86/pkeys: Standardize on u8 for pkey type |
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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?
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