From: Joerg Roedel <joerg.roedel-5C7GfCeVMHo@public.gmane.org>
To: "Alexandra N. Kossovsky"
<Alexandra.Kossovsky-mK/T7fl7eHLILq5++fvS8w@public.gmane.org>
Cc: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org,
Robert Stonehouse
<rstonehouse-s/n/eUQHGBpZroRs9YW3xA@public.gmane.org>
Subject: Re: atomic context for iommu_map call
Date: Tue, 26 Jun 2012 10:58:53 +0200 [thread overview]
Message-ID: <20120626085853.GX2624@amd.com> (raw)
In-Reply-To: <20120622112812.GV8140-mK/T7fl7eHLILq5++fvS8w@public.gmane.org>
On Fri, Jun 22, 2012 at 03:28:14PM +0400, Alexandra N. Kossovsky wrote:
> Hello.
>
> It is not clear from the documentation if iommu_map()/iommu_unmap()
> functions may be called from atomic context.
> In case of Intel IOMMU, it works; in case of AMD IOMMU, it does not.
>
> Was it done by purpose? May I propose a patch for AMD IOMMU replacing
> GFP_KERNEL by GFP_ATOMIC to make things better?
Well, a better option would be to have an iommu_map_atomic() alongside
the current iommu_map API call.
> We use IOMMU API in OpenOnload project http://www.openonload.org/,
> and we get better latency with Intel IOMMU because we are not
> forced to use threaded IRQ.
Yes, the IRQ for the AMD IOMMU is threaded. But I don't understand how
that is relevant for your latency. Can you give more details here?
Joerg
--
AMD Operating System Research Center
Advanced Micro Devices GmbH Einsteinring 24 85609 Dornach
General Managers: Alberto Bozzo
Registration: Dornach, Landkr. Muenchen; Registerger. Muenchen, HRB Nr. 43632
next prev parent reply other threads:[~2012-06-26 8:58 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-22 11:28 atomic context for iommu_map call Alexandra N. Kossovsky
[not found] ` <20120622112812.GV8140-mK/T7fl7eHLILq5++fvS8w@public.gmane.org>
2012-06-25 18:35 ` Chris Wright
2012-06-26 8:58 ` Joerg Roedel [this message]
[not found] ` <20120626085853.GX2624-5C7GfCeVMHo@public.gmane.org>
2012-06-26 9:08 ` Alexandra N. Kossovsky
2012-06-26 18:07 ` Chris Wright
[not found] ` <20120626180743.GV15796-JyIX8gxvWYPr2PDY2+4mTGD2FQJk+8+b@public.gmane.org>
2012-07-09 9:42 ` Joerg Roedel
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