From: Julien Grall <julien.grall@linaro.org>
To: xen-devel@lists.xenproject.org
Cc: stefano.stabellini@citrix.com, tim@xen.org, ian.campbell@citrix.com
Subject: Re: [PATCH v7 2/4] xen/arm: grant: Add another entry to map MFN 1:1 in dom0 p2m
Date: Sat, 17 May 2014 19:12:04 +0100 [thread overview]
Message-ID: <5377A674.8090806@linaro.org> (raw)
In-Reply-To: <1400163385-19863-3-git-send-email-julien.grall@linaro.org>
On 15/05/14 15:16, Julien Grall wrote:
> Grant mapping can be used for DMA request. The dev_bus_addr returned by the
> hypercall is the MFN (not the IPA). Currently Linux is using this address (via
> swiotlb) to program the DMA.
> When the device is protected by IOMMU the request will fail. We have to
> add 1:1 mapping in the domain p2m to allow DMA request working.
>
> This is valid because DOM0 has its memory mapped 1:1 and therefore we know
> that RAM and devices cannot clash.
I though a bit more about this patch. It doesn't handle the case where 2
grant use the same MFN, which is valid.
In this case, we should remove the 1:1 mapping only when the last grant
is removed.
I'm not sure how to handle this case.
Regards,
--
Julien Grall
next prev parent reply other threads:[~2014-05-17 18:12 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-15 14:16 [PATCH v7 0/4] IOMMU support for ARM Julien Grall
2014-05-15 14:16 ` [PATCH v7 1/4] xen/arm: p2m: Clean cache PT when the IOMMU doesn't support coherent walk Julien Grall
2014-05-15 15:20 ` Ian Campbell
2014-05-15 15:24 ` Julien Grall
2014-05-15 15:51 ` Ian Campbell
2014-05-15 16:05 ` Jan Beulich
2014-05-15 16:04 ` Jan Beulich
2014-05-15 17:06 ` Julien Grall
2014-05-16 10:00 ` Ian Campbell
2014-05-15 14:16 ` [PATCH v7 2/4] xen/arm: grant: Add another entry to map MFN 1:1 in dom0 p2m Julien Grall
2014-05-17 18:12 ` Julien Grall [this message]
2014-05-19 9:45 ` Ian Campbell
2014-05-19 14:20 ` Julien Grall
2014-05-20 7:30 ` Roger Pau Monné
2014-05-20 8:51 ` Ian Campbell
2014-05-20 11:19 ` Julien Grall
2014-05-20 11:25 ` Ian Campbell
2014-05-20 11:53 ` Julien Grall
2014-05-15 14:16 ` [PATCH v7 3/4] xen: iommu: Define PAGE_{SHIFT, SIZE, ALIGN, MASK)_64K Julien Grall
2014-05-15 14:16 ` [PATCH v7 4/4] drivers/passthrough: arm: Add support for SMMU drivers Julien Grall
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