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From: Jason Gunthorpe <jgg@ziepe.ca>
To: Christoph Hellwig <hch@lst.de>
Cc: Bjorn Helgaas <bhelgaas@google.com>,
	linux-rdma@vger.kernel.org, iommu@lists.linux-foundation.org,
	Logan Gunthorpe <logang@deltatee.com>,
	linux-pci@vger.kernel.org
Subject: Re: [PATCH 2/5] RDMA/core: remove use of dma_virt_ops
Date: Wed, 4 Nov 2020 09:42:41 -0400	[thread overview]
Message-ID: <20201104134241.GP36674@ziepe.ca> (raw)
In-Reply-To: <20201104095052.1222754-3-hch@lst.de>

On Wed, Nov 04, 2020 at 10:50:49AM +0100, Christoph Hellwig wrote:

> +int ib_dma_virt_map_sg(struct ib_device *dev, struct scatterlist *sg, int nents)
> +{
> +	struct scatterlist *s;
> +	int i;
> +
> +	for_each_sg(sg, s, nents, i) {
> +		sg_dma_address(s) = (uintptr_t)sg_virt(s);
> +		sg_dma_len(s) = s->length;

Hmm.. There is nothing ensuring the page is mapped here for this
sg_virt(). Before maybe some of the kconfig stuff prevented highmem
systems indirectly, I wonder if we should add something more direct to
exclude highmem for these drivers?

Sigh. I think the proper fix is to replace addr/length with a
scatterlist pointer in the struct ib_sge, then have SW drivers
directly use the page pointer properly.

Then just delete this stuff, all drivers need is a noop dmaops

Looks a lot hard though, so we should probably go ahead with this.

Jason
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WARNING: multiple messages have this Message-ID (diff)
From: Jason Gunthorpe <jgg@ziepe.ca>
To: Christoph Hellwig <hch@lst.de>
Cc: Bjorn Helgaas <bhelgaas@google.com>,
	Logan Gunthorpe <logang@deltatee.com>,
	linux-rdma@vger.kernel.org, linux-pci@vger.kernel.org,
	iommu@lists.linux-foundation.org
Subject: Re: [PATCH 2/5] RDMA/core: remove use of dma_virt_ops
Date: Wed, 4 Nov 2020 09:42:41 -0400	[thread overview]
Message-ID: <20201104134241.GP36674@ziepe.ca> (raw)
In-Reply-To: <20201104095052.1222754-3-hch@lst.de>

On Wed, Nov 04, 2020 at 10:50:49AM +0100, Christoph Hellwig wrote:

> +int ib_dma_virt_map_sg(struct ib_device *dev, struct scatterlist *sg, int nents)
> +{
> +	struct scatterlist *s;
> +	int i;
> +
> +	for_each_sg(sg, s, nents, i) {
> +		sg_dma_address(s) = (uintptr_t)sg_virt(s);
> +		sg_dma_len(s) = s->length;

Hmm.. There is nothing ensuring the page is mapped here for this
sg_virt(). Before maybe some of the kconfig stuff prevented highmem
systems indirectly, I wonder if we should add something more direct to
exclude highmem for these drivers?

Sigh. I think the proper fix is to replace addr/length with a
scatterlist pointer in the struct ib_sge, then have SW drivers
directly use the page pointer properly.

Then just delete this stuff, all drivers need is a noop dmaops

Looks a lot hard though, so we should probably go ahead with this.

Jason

  reply	other threads:[~2020-11-04 13:49 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-04  9:50 remove dma_virt_ops Christoph Hellwig
2020-11-04  9:50 ` Christoph Hellwig
2020-11-04  9:50 ` [PATCH 1/5] RDMA/core: remove ib_dma_{alloc,free}_coherent Christoph Hellwig
2020-11-04  9:50   ` Christoph Hellwig
2020-11-04  9:50 ` [PATCH 2/5] RDMA/core: remove use of dma_virt_ops Christoph Hellwig
2020-11-04  9:50   ` Christoph Hellwig
2020-11-04 13:42   ` Jason Gunthorpe [this message]
2020-11-04 13:42     ` Jason Gunthorpe
2020-11-04 14:01     ` Christoph Hellwig
2020-11-04 14:01       ` Christoph Hellwig
2020-11-04 15:09       ` Bernard Metzler
2020-11-04 15:09         ` Bernard Metzler
2020-11-04 18:10         ` Jason Gunthorpe
2020-11-04 18:10           ` Jason Gunthorpe
2020-11-04 15:52       ` Jason Gunthorpe
2020-11-04 15:52         ` Jason Gunthorpe
2020-11-04 16:31         ` Christoph Hellwig
2020-11-04 16:31           ` Christoph Hellwig
2020-11-04 18:09           ` Jason Gunthorpe
2020-11-04 18:09             ` Jason Gunthorpe
2020-11-04  9:50 ` [PATCH 3/5] PCI/p2p: remove the DMA_VIRT_OPS hacks Christoph Hellwig
2020-11-04  9:50   ` Christoph Hellwig
2020-11-04 16:53   ` Bjorn Helgaas
2020-11-04 16:53     ` Bjorn Helgaas
2020-11-04 17:00   ` Logan Gunthorpe
2020-11-04 17:00     ` Logan Gunthorpe
2020-11-04  9:50 ` [PATCH 4/5] PCI/p2p: cleanup up __pci_p2pdma_map_sg a bit Christoph Hellwig
2020-11-04  9:50   ` Christoph Hellwig
2020-11-04 16:54   ` Bjorn Helgaas
2020-11-04 16:54     ` Bjorn Helgaas
2020-11-04  9:50 ` [PATCH 5/5] dma-mapping: remove dma_virt_ops Christoph Hellwig
2020-11-04  9:50   ` Christoph Hellwig

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