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From: Ira Weiny <ira.weiny@intel.com>
To: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
Cc: "hpa@zytor.com" <hpa@zytor.com>,
	"Williams, Dan J" <dan.j.williams@intel.com>,
	"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
	"Yu, Fenghua" <fenghua.yu@intel.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH V8 16/44] mm/pkeys: Introduce pks_mk_readwrite()
Date: Thu, 17 Feb 2022 18:22:33 -0800	[thread overview]
Message-ID: <Yg8C6UkgfBmQlPSq@iweiny-desk3> (raw)
In-Reply-To: <a1f74401512ee19176397633aa823f9b6e375973.camel@intel.com>

On Mon, Jan 31, 2022 at 03:10:39PM -0800, Edgecombe, Rick P wrote:
> On Thu, 2022-01-27 at 09:54 -0800, ira.weiny@intel.com wrote:
> > +void pks_update_protection(int pkey, u32 protection)
> > +{
> 
> I don't know if this matters too much, but the type of a pkey is either
> int or u16 across this series and PKU. But it's only possibly a 4 bit
> value.

I was settling on 'int' because the PKRU code uses int a lot.

That said, PKRU is a bit more complicated; x86 is 4 bits, powerpc is 5 bits,
and I see 4 different types for pkey [int, u16, u32, s16].

The signed values are used to mean 'key or error' in a couple of places.  Which
leaves 'int' as a convenient choice over 's16' IMO.  The use of u32 and u16
seems arbitrary.  Both should be plenty big for generic core code.

> Seems the smallest that would fit is char. Why use one over the
> other?
> 
> Also, why u32 for protection here? The whole pkrs value containing the
> bits for all keys is 32 bits, but per key there is only room ever for 2
> bits, right?

Correct but I'm not sure anything would be saved by declaring u8.  Regardless
I've changed it.

> 
> It would be nice to be consistent and have a reason, but again, I don't
> know if makes any real difference.

I was consistent in the core code with 'int'.  I'll look at cleaning up some of
the PKRU code but I think that is a separate series from this one.

For this series I'll standardize on u8 because u16 is also too big.  I have
seen one place where it would be nice to have a type of unsigned to check the
bounds of the pkey.  So you have a valid point that following the PKRU code was
less than ideal.

Ira

  reply	other threads:[~2022-02-18  2:22 UTC|newest]

Thread overview: 145+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-27 17:54 [PATCH V8 00/44] PKS/PMEM: Add Stray Write Protection ira.weiny
2022-01-27 17:54 ` [PATCH V8 01/44] entry: Create an internal irqentry_exit_cond_resched() call ira.weiny
2022-01-27 17:54 ` [PATCH V8 02/44] Documentation/protection-keys: Clean up documentation for User Space pkeys ira.weiny
2022-01-28 22:39   ` Dave Hansen
2022-02-01 23:49     ` Ira Weiny
2022-02-01 23:54       ` Dave Hansen
2022-01-27 17:54 ` [PATCH V8 03/44] x86/pkeys: Create pkeys_common.h ira.weiny
2022-01-28 22:43   ` Dave Hansen
2022-02-02  1:00     ` Ira Weiny
2022-01-27 17:54 ` [PATCH V8 04/44] x86/pkeys: Add additional PKEY helper macros ira.weiny
2022-01-28 22:47   ` Dave Hansen
2022-02-02 20:21     ` Ira Weiny
2022-02-02 20:26       ` Dave Hansen
2022-02-02 20:28         ` Ira Weiny
2022-01-27 17:54 ` [PATCH V8 05/44] x86/fpu: Refactor arch_set_user_pkey_access() ira.weiny
2022-01-28 22:50   ` Dave Hansen
2022-02-02 20:22     ` Ira Weiny
2022-01-27 17:54 ` [PATCH V8 06/44] mm/pkeys: Add Kconfig options for PKS ira.weiny
2022-01-28 22:54   ` Dave Hansen
2022-01-28 23:10     ` Ira Weiny
2022-01-28 23:51       ` Dave Hansen
2022-02-04 19:08         ` Ira Weiny
2022-02-09  5:34           ` Ira Weiny
2022-02-14 19:20             ` Dave Hansen
2022-02-14 23:03               ` Ira Weiny
2022-01-29  0:06   ` Dave Hansen
2022-02-04 19:14     ` Ira Weiny
2022-01-27 17:54 ` [PATCH V8 07/44] x86/pkeys: Add PKS CPU feature bit ira.weiny
2022-01-28 23:05   ` Dave Hansen
2022-02-04 19:21     ` Ira Weiny
2022-01-27 17:54 ` [PATCH V8 08/44] x86/fault: Adjust WARN_ON for PKey fault ira.weiny
2022-01-28 23:10   ` Dave Hansen
2022-02-04 20:06     ` Ira Weiny
2022-01-27 17:54 ` [PATCH V8 09/44] x86/pkeys: Enable PKS on cpus which support it ira.weiny
2022-01-28 23:18   ` Dave Hansen
2022-01-28 23:41     ` Ira Weiny
2022-01-28 23:53       ` Dave Hansen
2022-01-27 17:54 ` [PATCH V8 10/44] Documentation/pkeys: Add initial PKS documentation ira.weiny
2022-01-28 23:57   ` Dave Hansen
2022-01-27 17:54 ` [PATCH V8 11/44] mm/pkeys: Define static PKS key array and default values ira.weiny
2022-01-29  0:02   ` Dave Hansen
2022-02-04 23:54     ` Ira Weiny
2022-01-27 17:54 ` [PATCH V8 12/44] mm/pkeys: Define PKS page table macros ira.weiny
2022-01-27 17:54 ` [PATCH V8 13/44] mm/pkeys: Add initial PKS Test code ira.weiny
2022-01-31 19:30   ` Edgecombe, Rick P
2022-02-09 23:44     ` Ira Weiny
2022-01-27 17:54 ` [PATCH V8 14/44] x86/pkeys: Introduce pks_write_pkrs() ira.weiny
2022-01-29  0:12   ` Dave Hansen
2022-01-29  0:16     ` Ira Weiny
2022-01-27 17:54 ` [PATCH V8 15/44] x86/pkeys: Preserve the PKS MSR on context switch ira.weiny
2022-01-29  0:22   ` Dave Hansen
2022-02-11  6:10     ` Ira Weiny
2022-01-27 17:54 ` [PATCH V8 16/44] mm/pkeys: Introduce pks_mk_readwrite() ira.weiny
2022-01-31 23:10   ` Edgecombe, Rick P
2022-02-18  2:22     ` Ira Weiny [this message]
2022-02-01 17:40   ` Dave Hansen
2022-02-18  4:39     ` Ira Weiny
2022-01-27 17:54 ` [PATCH V8 17/44] mm/pkeys: Introduce pks_mk_noaccess() ira.weiny
2022-01-27 17:54 ` [PATCH V8 18/44] x86/fault: Add a PKS test fault hook ira.weiny
2022-01-31 19:56   ` Edgecombe, Rick P
2022-02-11 20:40     ` Ira Weiny
2022-01-27 17:54 ` [PATCH V8 19/44] mm/pkeys: PKS Testing, add pks_mk_*() tests ira.weiny
2022-02-01 17:45   ` Dave Hansen
2022-02-18  5:34     ` Ira Weiny
2022-02-18 15:28       ` Dave Hansen
2022-02-18 17:25         ` Ira Weiny
2022-01-27 17:54 ` [PATCH V8 20/44] mm/pkeys: Add PKS test for context switching ira.weiny
2022-02-01 17:43   ` Edgecombe, Rick P
2022-02-22 21:42     ` Ira Weiny
2022-02-01 17:47   ` Edgecombe, Rick P
2022-02-01 19:52     ` Edgecombe, Rick P
2022-02-18  6:03       ` Ira Weiny
2022-02-18  6:02     ` Ira Weiny
2022-01-27 17:54 ` [PATCH V8 21/44] x86/entry: Add auxiliary pt_regs space ira.weiny
2022-01-27 17:54 ` [PATCH V8 22/44] entry: Pass pt_regs to irqentry_exit_cond_resched() ira.weiny
2022-01-27 17:54 ` [PATCH V8 23/44] entry: Add architecture auxiliary pt_regs save/restore calls ira.weiny
2022-01-27 17:54 ` [PATCH V8 24/44] x86/entry: Define arch_{save|restore}_auxiliary_pt_regs() ira.weiny
2022-01-27 17:54 ` [PATCH V8 25/44] x86/pkeys: Preserve PKRS MSR across exceptions ira.weiny
2022-01-27 17:54 ` [PATCH V8 26/44] x86/fault: Print PKS MSR on fault ira.weiny
2022-02-01 18:13   ` Edgecombe, Rick P
2022-02-18  6:01     ` Ira Weiny
2022-02-18 17:28       ` Edgecombe, Rick P
2022-02-18 20:20         ` Dave Hansen
2022-02-18 20:54           ` Ira Weiny
2022-01-27 17:54 ` [PATCH V8 27/44] mm/pkeys: Add PKS exception test ira.weiny
2022-01-27 17:54 ` [PATCH V8 28/44] mm/pkeys: Introduce pks_update_exception() ira.weiny
2022-01-27 17:54 ` [PATCH V8 29/44] mm/pkeys: Introduce PKS fault callbacks ira.weiny
2022-01-27 17:54 ` [PATCH V8 30/44] mm/pkeys: Test setting a PKS key in a custom fault callback ira.weiny
2022-02-01  0:55   ` Edgecombe, Rick P
2022-03-01 15:39     ` Ira Weiny
2022-02-01 17:42   ` Edgecombe, Rick P
2022-02-11 20:44     ` Ira Weiny
2022-01-27 17:54 ` [PATCH V8 31/44] mm/pkeys: Add pks_available() ira.weiny
2022-01-27 17:54 ` [PATCH V8 32/44] memremap_pages: Add Kconfig for DEVMAP_ACCESS_PROTECTION ira.weiny
2022-02-04 15:49   ` Dan Williams
2022-01-27 17:54 ` [PATCH V8 33/44] memremap_pages: Introduce pgmap_protection_available() ira.weiny
2022-02-04 16:19   ` Dan Williams
2022-02-28 16:59     ` Ira Weiny
2022-03-01 15:56       ` Ira Weiny
2022-01-27 17:54 ` [PATCH V8 34/44] memremap_pages: Introduce a PGMAP_PROTECTION flag ira.weiny
2022-01-27 17:54 ` [PATCH V8 35/44] memremap_pages: Introduce devmap_protected() ira.weiny
2022-01-27 17:54 ` [PATCH V8 36/44] memremap_pages: Reserve a PKS PKey for eventual use by PMEM ira.weiny
2022-02-01 18:35   ` Edgecombe, Rick P
2022-02-04 17:12     ` Dan Williams
2022-02-05  5:40       ` Ira Weiny
2022-02-05  8:19         ` Dan Williams
2022-02-06 18:14           ` Dan Williams
2022-02-08 22:48           ` Ira Weiny
2022-02-08 23:22             ` Dan Williams
2022-02-08 23:42               ` Ira Weiny
2022-01-27 17:54 ` [PATCH V8 37/44] memremap_pages: Set PKS PKey in PTEs if PGMAP_PROTECTIONS is requested ira.weiny
2022-02-04 17:41   ` Dan Williams
2022-03-01 18:15     ` Ira Weiny
2022-01-27 17:54 ` [PATCH V8 38/44] memremap_pages: Define pgmap_mk_{readwrite|noaccess}() calls ira.weiny
2022-02-04 18:35   ` Dan Williams
2022-02-05  0:09     ` Ira Weiny
2022-02-05  0:19       ` Dan Williams
2022-02-05  0:25         ` Dan Williams
2022-02-05  0:27           ` Dan Williams
2022-02-05  5:55             ` Ira Weiny
2022-02-05  6:28               ` Dan Williams
2022-02-22 22:05     ` Ira Weiny
2022-01-27 17:55 ` [PATCH V8 39/44] memremap_pages: Add memremap.pks_fault_mode ira.weiny
2022-02-01  1:16   ` Edgecombe, Rick P
2022-03-02  0:20     ` Ira Weiny
2022-02-04 19:01   ` Dan Williams
2022-03-02  2:00     ` Ira Weiny
2022-01-27 17:55 ` [PATCH V8 40/44] memremap_pages: Add pgmap_protection_flag_invalid() ira.weiny
2022-02-01  1:37   ` Edgecombe, Rick P
2022-03-02  2:01     ` Ira Weiny
2022-02-04 19:18   ` Dan Williams
2022-01-27 17:55 ` [PATCH V8 41/44] kmap: Ensure kmap works for devmap pages ira.weiny
2022-02-04 21:07   ` Dan Williams
2022-03-01 19:45     ` Ira Weiny
2022-03-01 19:50       ` Ira Weiny
2022-03-01 20:05       ` Dan Williams
2022-03-01 23:03         ` Ira Weiny
2022-01-27 17:55 ` [PATCH V8 42/44] dax: Stray access protection for dax_direct_access() ira.weiny
2022-02-04  5:19   ` Dan Williams
2022-03-01 18:13     ` Ira Weiny
2022-01-27 17:55 ` [PATCH V8 43/44] nvdimm/pmem: Enable stray access protection ira.weiny
2022-02-04 21:10   ` Dan Williams
2022-03-01 18:18     ` Ira Weiny
2022-01-27 17:55 ` [PATCH V8 44/44] devdax: " ira.weiny
2022-02-04 21:12   ` Dan Williams

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