From: Sowmini Varadhan <sowmini.varadhan@oracle.com>
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Guenter Roeck <linux@roeck-us.net>,
linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
benh@kernel.crashing.org, davem@davemloft.net
Subject: Re: [PATCH] iommu-common: Do not use 64 bit constant 0xffffffffffffffffl for computing align_mask
Date: Mon, 20 Jul 2015 21:25:31 +0200 [thread overview]
Message-ID: <20150720192531.GB19855@oracle.com> (raw)
In-Reply-To: <87oaj6ogox.fsf@rasmusvillemoes.dk>
On (07/20/15 19:57), Rasmus Villemoes wrote:
> I highly doubt it. The result is truncated to unsigned long
> anyway. Assuming align_order always has a value between 0 and
> BITS_PER_LONG, GENMASK should be exactly what is wanted.
While GENMASK may do the job, the code is already quite obscure,
so I'm going to stick with the minimal delta to get this right,
namely
- align_mask = 0xffffffffffffffffl >> (64 - align_order);
+ align_mask = ~0ul >> (BITS_PER_LONG - align_order);
--Sowmini
next prev parent reply other threads:[~2015-07-20 19:26 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-19 12:20 [PATCH] iommu-common: Do not use 64 bit constant 0xffffffffffffffffl for computing align_mask Sowmini Varadhan
2015-07-19 15:27 ` Guenter Roeck
2015-07-19 20:25 ` Rasmus Villemoes
2015-07-19 20:41 ` Sowmini Varadhan
2015-07-20 1:58 ` Guenter Roeck
2015-07-20 17:57 ` Rasmus Villemoes
2015-07-20 19:25 ` Sowmini Varadhan [this message]
2015-07-20 23:28 ` Andrew Morton
2015-07-21 0:26 ` Guenter Roeck
2015-07-20 14:44 ` Sowmini Varadhan
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