From: Andi Kleen <andi@firstfloor.org>
To: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: "Prakash, Sathya" <Sathya.Prakash@lsi.com>, linux-scsi@vger.kernel.org
Subject: Re: Query regarding modifying the DMA Mask based on the available memory in the system
Date: Thu, 17 Apr 2008 17:06:50 +0200 [thread overview]
Message-ID: <4807678A.8020906@firstfloor.org> (raw)
In-Reply-To: <1208444622.3150.10.camel@localhost.localdomain>
James Bottomley wrote:
> On Thu, 2008-04-17 at 16:44 +0200, Andi Kleen wrote:
>>> For drivers that can alter their descriptor types, we have this
>>> function:
>>>
>>> dma_get_required_mask()
>> Are you sure we have it? It seems to be in drivers/base/platform.c
>> conditional on ARCH_HAS_DMA_GET_REQUIRED_MASK, but according to my
>> grep no architecture ever sets that flag.
>
> Yes ... positive. That's the default and correct implementation based
> on the largest addressable physical memory.
Ok but still the whole thing is completely useless right now.
>> I don't think it would be very hard to implement on x86 at least,
>> mind you. Just nobody seems to have done it so far.
>
> Really, only machines with IOMMUs that want to restrict this need
> implement it.
I don't think so. For once in the scenario described by the original
poster it makes some sense even without IOMMU.
-Andi
next prev parent reply other threads:[~2008-04-17 15:06 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-04-17 8:40 Query regarding modifying the DMA Mask based on the available memory in the system Prakash, Sathya
2008-04-17 8:43 ` David Miller
2008-04-17 10:06 ` Andi Kleen
2008-04-17 14:18 ` James Bottomley
2008-04-17 14:44 ` Andi Kleen
2008-04-17 15:03 ` James Bottomley
2008-04-17 15:06 ` Andi Kleen [this message]
2008-04-17 15:36 ` James Bottomley
2008-04-17 16:10 ` Andi Kleen
-- strict thread matches above, loose matches on Subject: below --
2008-04-17 17:36 Prakash, Sathya
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