Re: [PATCH 5/5] x86/pkeys: Standardize on u8 for pkey type
On Tue, Mar 15, 2022 at 09:03:26AM -0700, Dave Hansen wrote: > 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.we...@intel.com wrote: > >>> From: Ira Weiny > >>> > >>> 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. Ah yea that needs to be sorted out too I think. > > >> 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? I don't mind at all. Ira
Re: [PATCH 5/5] x86/pkeys: Standardize on u8 for pkey type
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.we...@intel.com wrote: >>> From: Ira Weiny >>> >>> 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?
Re: [PATCH 5/5] x86/pkeys: Standardize on u8 for pkey type
On Mon, Mar 14, 2022 at 04:49:12PM -0700, Dave Hansen wrote: > On 3/10/22 16:57, ira.we...@intel.com wrote: > > From: Ira Weiny > > > > 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); > > Also if we're worried about the type needing to change 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. Ira
Re: [PATCH 5/5] x86/pkeys: Standardize on u8 for pkey type
On 3/10/22 16:57, ira.we...@intel.com wrote: > From: Ira Weiny > > 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. Also if we're worried about the type needing to change or with the wrong type being used, I guess we could just to a pkey_t typedef.
