From: "Koenig, Christian" <Christian.Koenig@amd.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Logan Gunthorpe <logang@deltatee.com>,
"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
Bjorn Helgaas <bhelgaas@google.com>
Subject: Re: [PATCH] PCI/P2PDMA: Root complex whitelist should not apply when an IOMMU is present
Date: Thu, 23 May 2019 09:48:40 +0000 [thread overview]
Message-ID: <fa941625-ef65-74fa-e232-705ea5acefa3@amd.com> (raw)
In-Reply-To: <20190523094322.GA14986@lst.de>
Am 23.05.19 um 11:43 schrieb Christoph Hellwig:
> [CAUTION: External Email]
>
> On Thu, May 23, 2019 at 08:12:18AM +0000, Koenig, Christian wrote:
>>> Are you DMA-mapping the addresses outside the P2PDMA code? If so there's
>>> a huge mismatch with the existing users of P2PDMA (nvme-fabrics). If
>>> you're not dma-mapping then I can't see how it could work because the
>>> IOMMU should reject any requests to access those addresses.
>> Well, we are using the DMA API (dma_map_resource) for this. If the P2P
>> code is not using this then I would rather say that the P2P code is
>> actually broken.
>>
>> Adding Christoph as well, cause he is usually the one discussion stuff
>> like that with me.
> Heh. Actually dma_map_resource-ish APIs are the right thing to do,
> but I'm not sure how you managed to be able to use it for PCIe P2P
> yet, as it fails to account for any difference in the PCIe level
> "physical" address with the hosts view of "physical" addresses.
>
> Do these offsets now how up on AMD platforms? Do you adjust for them
> elsewhere?
I don't adjust the address manually anywhere. I just call
dma_map_resource() and use the resulting DMA address to access the other
devices PCI BAR.
At least on my test system (AMD CPU + AMD GPUs) this seems to work
totally fine. Currently trying to find time and an Intel box to test it
there as well.
Regards,
Christian.
next prev parent reply other threads:[~2019-05-23 9:48 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <a98bff67-a76e-4ddc-a317-96f2bdc9af72@email.android.com>
2019-05-22 20:41 ` [PATCH] PCI/P2PDMA: Root complex whitelist should not apply when an IOMMU is present Logan Gunthorpe
2019-05-23 8:12 ` Koenig, Christian
2019-05-23 9:43 ` Christoph Hellwig
2019-05-23 9:48 ` Koenig, Christian [this message]
2019-05-23 9:50 ` Christoph Hellwig
2019-05-23 10:06 ` Koenig, Christian
2019-05-23 10:26 ` Christoph Hellwig
2019-05-23 15:59 ` Logan Gunthorpe
2019-05-23 15:53 ` Logan Gunthorpe
2019-05-23 15:59 ` Christoph Hellwig
2019-05-24 12:40 ` Koenig, Christian
2019-05-24 14:12 ` Christoph Hellwig
2019-05-24 16:18 ` Logan Gunthorpe
2019-05-24 16:06 ` Logan Gunthorpe
2019-05-23 16:14 ` Logan Gunthorpe
2019-05-23 15:47 ` Logan Gunthorpe
2019-05-22 20:12 Logan Gunthorpe
2019-06-18 20:40 ` Bjorn Helgaas
2019-06-18 20:51 ` Logan Gunthorpe
2019-06-18 23:50 ` Logan Gunthorpe
2019-06-19 9:26 ` Koenig, Christian
2019-06-19 9:29 ` Christoph Hellwig
2019-06-19 9:39 ` Koenig, Christian
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