From: Olof Johansson <olof@lixom.net>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: linuxppc-dev list <linuxppc-dev@ozlabs.org>,
Paul Mackerras <paulus@samba.org>,
Linux Kernel list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH][POWERPC] Workaround for iommu page alignment
Date: Mon, 7 Jan 2008 15:57:56 -0600 [thread overview]
Message-ID: <20080107215755.GA31230@lixom.net> (raw)
In-Reply-To: <1199742359.6734.14.camel@pasglop>
On Tue, Jan 08, 2008 at 08:45:59AM +1100, Benjamin Herrenschmidt wrote:
> Our iommu page size is currently always 4K. That means with our current
> code, drivers may do a dma_map_sg() of a 64K page and obtain a dma_addr_t
> that is only 4K aligned.
>
> This works fine in most cases except some infiniband HW it seems, where
> they tell the HW about the page size and it ignores the low bits of the
> DMA address.
>
> This works around it by making our IOMMU code enforce a PAGE_SIZE alignment
> for mappings of objects that are page aligned in the first place and whose
> size is larger or equal to a page.
>
> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Olof Johansson <olof@lixom.net>
-Olof
WARNING: multiple messages have this Message-ID (diff)
From: Olof Johansson <olof@lixom.net>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>,
linuxppc-dev list <linuxppc-dev@ozlabs.org>,
Linux Kernel list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH][POWERPC] Workaround for iommu page alignment
Date: Mon, 7 Jan 2008 15:57:56 -0600 [thread overview]
Message-ID: <20080107215755.GA31230@lixom.net> (raw)
In-Reply-To: <1199742359.6734.14.camel@pasglop>
On Tue, Jan 08, 2008 at 08:45:59AM +1100, Benjamin Herrenschmidt wrote:
> Our iommu page size is currently always 4K. That means with our current
> code, drivers may do a dma_map_sg() of a 64K page and obtain a dma_addr_t
> that is only 4K aligned.
>
> This works fine in most cases except some infiniband HW it seems, where
> they tell the HW about the page size and it ignores the low bits of the
> DMA address.
>
> This works around it by making our IOMMU code enforce a PAGE_SIZE alignment
> for mappings of objects that are page aligned in the first place and whose
> size is larger or equal to a page.
>
> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Olof Johansson <olof@lixom.net>
-Olof
next prev parent reply other threads:[~2008-01-07 21:48 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-01-07 21:45 [PATCH][POWERPC] Workaround for iommu page alignment Benjamin Herrenschmidt
2008-01-07 21:57 ` Olof Johansson [this message]
2008-01-07 21:57 ` Olof Johansson
2008-01-07 22:41 ` Michael Ellerman
2008-01-07 22:41 ` Michael Ellerman
2008-01-07 23:33 ` Benjamin Herrenschmidt
2008-01-07 23:33 ` Benjamin Herrenschmidt
2008-01-07 23:34 ` [PATCH][POWERPC] Workaround for iommu page alignment (#2) Benjamin Herrenschmidt
2008-01-08 3:48 ` Olof Johansson
2008-01-08 3:48 ` Olof Johansson
2008-01-08 4:02 ` Benjamin Herrenschmidt
2008-01-08 4:02 ` Benjamin Herrenschmidt
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