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From: Segher Boessenkool <segher@kernel.crashing.org>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: gjoyce@linux.ibm.com, Andrew Donnellan <ajd@linux.ibm.com>,
	erichte@linux.ibm.com, gregkh@linuxfoundation.org,
	nayna@linux.ibm.com, linux-kernel@vger.kernel.org,
	zohar@linux.ibm.com, sudhakar@linux.ibm.com, ruscur@russell.cc,
	joel@jms.id.au, bgray@linux.ibm.com,
	linux-integrity@vger.kernel.org, gcwilson@linux.ibm.com,
	linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v4 02/24] powerpc/pseries: Fix alignment of PLPKS structures and buffers
Date: Thu, 26 Jan 2023 11:19:25 -0600	[thread overview]
Message-ID: <20230126171925.GN25951@gate.crashing.org> (raw)
In-Reply-To: <87pmb2pxpa.fsf@mpe.ellerman.id.au>

On Thu, Jan 26, 2023 at 12:09:53AM +1100, Michael Ellerman wrote:
> Andrew Donnellan <ajd@linux.ibm.com> writes:
> > A number of structures and buffers passed to PKS hcalls have alignment
> > requirements, which could on occasion cause problems:
> >
> > - Authorisation structures must be 16-byte aligned and must not cross a
> >   page boundary
> >
> > - Label structures must not cross page boundaries
> >
> > - Password output buffers must not cross page boundaries
> >
> > Round up the allocations of these structures/buffers to the next power of
> > 2 to make sure this happens.
> 
> It's not the *next* power of 2, it's the *nearest* power of 2, including
> the initial value if it's already a power of 2.

It's not the nearest either, the nearest power of two to 65 is 64.  You
could say "but, round up" to which I would say "round?"  :-P

"Adjust the allocation size to be the smallest power of two greater than
or equal to the given size."

"Pad to a power of two" in shorthand.  "Padded to a power of two if
necessary" if you want to emphasise it can be a no-op.


Segher

  reply	other threads:[~2023-01-26 17:23 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-20  7:42 [PATCH v4 00/24] pSeries dynamic secure boot secvar interface + platform keyring loading Andrew Donnellan
2023-01-20  7:42 ` [PATCH v4 01/24] powerpc/pseries: Fix handling of PLPKS object flushing timeout Andrew Donnellan
2023-01-20  7:42 ` [PATCH v4 02/24] powerpc/pseries: Fix alignment of PLPKS structures and buffers Andrew Donnellan
2023-01-25 13:09   ` Michael Ellerman
2023-01-26 17:19     ` Segher Boessenkool [this message]
2023-01-26 17:31       ` David Laight
2023-01-27  3:20         ` Andrew Donnellan
2023-01-27  9:05           ` David Laight
2023-01-27 11:08           ` Michael Ellerman
2023-01-27 10:52       ` Michael Ellerman
2023-01-20  7:42 ` [PATCH v4 03/24] powerpc/secvar: Use u64 in secvar_operations Andrew Donnellan
2023-01-20  7:42 ` [PATCH v4 04/24] powerpc/secvar: Warn and error if multiple secvar ops are set Andrew Donnellan
2023-01-20  7:42 ` [PATCH v4 05/24] powerpc/secvar: Use sysfs_emit() instead of sprintf() Andrew Donnellan
2023-01-20  7:42 ` [PATCH v4 06/24] powerpc/secvar: Handle format string in the consumer Andrew Donnellan
2023-01-20  7:42 ` [PATCH v4 07/24] powerpc/secvar: Handle max object size " Andrew Donnellan
2023-01-20  7:42 ` [PATCH v4 08/24] powerpc/secvar: Clean up init error messages Andrew Donnellan
2023-01-20  7:42 ` [PATCH v4 09/24] powerpc/secvar: Extend sysfs to include config vars Andrew Donnellan
2023-01-20  7:42 ` [PATCH v4 10/24] powerpc/secvar: Allow backend to populate static list of variable names Andrew Donnellan
2023-01-20  7:42 ` [PATCH v4 11/24] powerpc/secvar: Warn when PAGE_SIZE is smaller than max object size Andrew Donnellan
2023-01-20  7:42 ` [PATCH v4 12/24] powerpc/secvar: Don't print error on ENOENT when reading variables Andrew Donnellan
2023-01-20  7:42 ` [PATCH v4 13/24] powerpc/pseries: Move plpks.h to include directory Andrew Donnellan
2023-01-20  7:42 ` [PATCH v4 14/24] powerpc/pseries: Move PLPKS constants to header file Andrew Donnellan
2023-01-20  7:42 ` [PATCH v4 15/24] powerpc/pseries: Expose PLPKS config values, support additional fields Andrew Donnellan
2023-01-20  7:42 ` [PATCH v4 16/24] powerpc/pseries: Implement signed update for PLPKS objects Andrew Donnellan
2023-01-24  4:16   ` Nicholas Piggin
2023-01-30  4:43     ` Andrew Donnellan
2023-01-31  4:23       ` Russell Currey
2023-01-20  7:42 ` [PATCH v4 17/24] powerpc/pseries: Log hcall return codes for PLPKS debug Andrew Donnellan
2023-01-20  7:43 ` [PATCH v4 18/24] powerpc/pseries: Make caller pass buffer to plpks_read_var() Andrew Donnellan
2023-01-20  7:43 ` [PATCH v4 19/24] powerpc/pseries: Turn PSERIES_PLPKS into a hidden option Andrew Donnellan
2023-01-24  4:26   ` Nicholas Piggin
2023-01-20  7:43 ` [PATCH v4 20/24] powerpc/pseries: Add helpers to get PLPKS password Andrew Donnellan
2023-01-20  7:43 ` [PATCH v4 21/24] powerpc/pseries: Pass PLPKS password on kexec Andrew Donnellan
2023-01-24  4:36   ` Nicholas Piggin
2023-01-24  4:40     ` Andrew Donnellan
2023-01-25  3:59       ` Michael Ellerman
2023-01-31  2:43     ` Russell Currey
2023-01-20  7:43 ` [PATCH v4 22/24] powerpc/pseries: Implement secvars for dynamic secure boot Andrew Donnellan
2023-01-24  5:17   ` Nicholas Piggin
2023-01-31  2:54     ` Andrew Donnellan
2023-01-31  4:25       ` Andrew Donnellan
2023-01-31  8:55       ` Nicholas Piggin
2023-02-01  2:15         ` Andrew Donnellan
2023-01-20  7:43 ` [PATCH v4 23/24] integrity/powerpc: Improve error handling & reporting when loading certs Andrew Donnellan
2023-01-24 15:42   ` Mimi Zohar
2023-01-20  7:43 ` [PATCH v4 24/24] integrity/powerpc: Support loading keys from pseries secvar Andrew Donnellan
2023-01-24  5:24   ` Nicholas Piggin
2023-01-24 15:14   ` Mimi Zohar
2023-01-25  0:45     ` Andrew Donnellan
2023-01-25  2:23     ` Russell Currey
2023-01-25  2:47       ` Mimi Zohar
2023-01-31  1:03         ` Andrew Donnellan

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