From: Roland Dreier <rdreier@cisco.com>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
linux-scsi@vger.kernel.org, rmk@arm.linux.org.uk,
davem@davemloft.net, james.bottomley@steeleye.com,
ralf@linux-mips.org
Subject: Re: [PATCH 2/2] scsi: Use new __dma_buffer to align sense buffer in scsi_cmnd
Date: Fri, 21 Dec 2007 08:57:47 -0800 [thread overview]
Message-ID: <adak5n8x9x0.fsf@cisco.com> (raw)
In-Reply-To: <20071221103326.7ce1bc4f@the-village.bc.nu> (Alan Cox's message of "Fri, 21 Dec 2007 10:33:26 +0000")
> It's also incomplete as a fix because I don't see what guarantees the
> buffer size will always exceed cache line size
There's a macro trick that adds a pad member after the buffer too, so
that it gets rounded up to the cacheline size:
> +#define __dma_aligned __attribute__((aligned(ARCH_MIN_DMA_ALIGNMENT)))
> +#define __dma_buffer __dma_buffer_line(__LINE__)
> +#define __dma_buffer_line(line) __dma_aligned;\
> + char __dma_pad_##line[0] __dma_aligned
So that part is OK at least.
- R.
WARNING: multiple messages have this Message-ID (diff)
From: Roland Dreier <rdreier@cisco.com>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
<linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
<linux-scsi@vger.kernel.org>, <rmk@arm.linux.org.uk>,
<davem@davemloft.net>, <james.bottomley@steeleye.com>,
<ralf@linux-mips.org>
Subject: Re: [PATCH 2/2] scsi: Use new __dma_buffer to align sense buffer in scsi_cmnd
Date: Fri, 21 Dec 2007 08:57:47 -0800 [thread overview]
Message-ID: <adak5n8x9x0.fsf@cisco.com> (raw)
In-Reply-To: <20071221103326.7ce1bc4f@the-village.bc.nu> (Alan Cox's message of "Fri, 21 Dec 2007 10:33:26 +0000")
> It's also incomplete as a fix because I don't see what guarantees the
> buffer size will always exceed cache line size
There's a macro trick that adds a pad member after the buffer too, so
that it gets rounded up to the cacheline size:
> +#define __dma_aligned __attribute__((aligned(ARCH_MIN_DMA_ALIGNMENT)))
> +#define __dma_buffer __dma_buffer_line(__LINE__)
> +#define __dma_buffer_line(line) __dma_aligned;\
> + char __dma_pad_##line[0] __dma_aligned
So that part is OK at least.
- R.
next prev parent reply other threads:[~2007-12-21 16:57 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-12-21 2:30 [PATCH 2/2] scsi: Use new __dma_buffer to align sense buffer in scsi_cmnd Benjamin Herrenschmidt
2007-12-21 2:30 ` Benjamin Herrenschmidt
2007-12-21 10:33 ` Alan Cox
2007-12-21 10:33 ` Alan Cox
2007-12-21 13:16 ` Matthew Wilcox
2007-12-21 13:30 ` Thomas Bogendoerfer
2007-12-21 14:00 ` Matthew Wilcox
2007-12-21 16:35 ` Thomas Bogendoerfer
2007-12-21 21:29 ` Benjamin Herrenschmidt
2007-12-21 16:57 ` Roland Dreier [this message]
2007-12-21 16:57 ` Roland Dreier
2007-12-21 21:27 ` Benjamin Herrenschmidt
2007-12-23 11:09 ` Boaz Harrosh
2007-12-23 23:04 ` Benjamin Herrenschmidt
2008-01-07 6:53 ` FUJITA Tomonori
2008-01-07 13:25 ` Boaz Harrosh
2008-01-07 23:32 ` FUJITA Tomonori
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