From: Don Dutile <ddutile@redhat.com>
To: John Hubbard <jhubbard@nvidia.com>,
Logan Gunthorpe <logang@deltatee.com>,
linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
linux-block@vger.kernel.org, linux-pci@vger.kernel.org,
linux-mm@kvack.org, iommu@lists.linux-foundation.org
Cc: "Stephen Bates" <sbates@raithlin.com>,
"Christoph Hellwig" <hch@lst.de>,
"Dan Williams" <dan.j.williams@intel.com>,
"Jason Gunthorpe" <jgg@ziepe.ca>,
"Christian König" <christian.koenig@amd.com>,
"Matthew Wilcox" <willy@infradead.org>,
"Daniel Vetter" <daniel.vetter@ffwll.ch>,
"Jakowski Andrzej" <andrzej.jakowski@intel.com>,
"Minturn Dave B" <dave.b.minturn@intel.com>,
"Jason Ekstrand" <jason@jlekstrand.net>,
"Dave Hansen" <dave.hansen@linux.intel.com>,
"Xiong Jianxin" <jianxin.xiong@intel.com>,
"Bjorn Helgaas" <helgaas@kernel.org>,
"Ira Weiny" <ira.weiny@intel.com>,
"Robin Murphy" <robin.murphy@arm.com>
Subject: Re: [PATCH 03/16] PCI/P2PDMA: Attempt to set map_type if it has not been set
Date: Tue, 11 May 2021 12:05:49 -0400 [thread overview]
Message-ID: <87a2b8e9-f0ef-ec23-8427-3022a86b0ec5@redhat.com> (raw)
In-Reply-To: <3834be62-3d1b-fc98-d793-e7dcb0a74624@nvidia.com>
On 5/2/21 3:58 PM, John Hubbard wrote:
> On 4/8/21 10:01 AM, Logan Gunthorpe wrote:
>> Attempt to find the mapping type for P2PDMA pages on the first
>> DMA map attempt if it has not been done ahead of time.
>>
>> Previously, the mapping type was expected to be calculated ahead of
>> time, but if pages are to come from userspace then there's no
>> way to ensure the path was checked ahead of time.
>>
>> Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
>> ---
>> drivers/pci/p2pdma.c | 12 +++++++++---
>> 1 file changed, 9 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
>> index 473a08940fbc..2574a062a255 100644
>> --- a/drivers/pci/p2pdma.c
>> +++ b/drivers/pci/p2pdma.c
>> @@ -825,11 +825,18 @@ EXPORT_SYMBOL_GPL(pci_p2pmem_publish);
>> static enum pci_p2pdma_map_type pci_p2pdma_map_type(struct pci_dev *provider,
>> struct pci_dev *client)
>> {
>> + enum pci_p2pdma_map_type ret;
>> +
>> if (!provider->p2pdma)
>> return PCI_P2PDMA_MAP_NOT_SUPPORTED;
>> - return xa_to_value(xa_load(&provider->p2pdma->map_types,
>> - map_types_idx(client)));
>> + ret = xa_to_value(xa_load(&provider->p2pdma->map_types,
>> + map_types_idx(client)));
>> + if (ret != PCI_P2PDMA_MAP_UNKNOWN)
>> + return ret;
>> +
>> + return upstream_bridge_distance_warn(provider, client, NULL,
>> + GFP_ATOMIC);
>
> Returning a "bridge distance" from a "get map type" routine is jarring,
> and I think it is because of a pre-existing problem: the above function
> is severely misnamed. Let's try renaming it (and the other one) to
> approximately:
>
> upstream_bridge_map_type_warn()
> upstream_bridge_map_type()
>
> ...and that should fix that. Well, that, plus tweaking the kernel doc
> comments, which are also confused. I think someone started off thinking
> about distances through PCIe, but in the end, the routine boils down to
> just a few situations that are not distances at all.
>
+1. didn't like the 'distance' check for a 'connection check" in the beginning, and looks like this is the time to clean it out.
:)
> Also, the above will read a little better if it is written like this:
>
> ret = xa_to_value(xa_load(&provider->p2pdma->map_types,
> map_types_idx(client)));
>
> if (ret == PCI_P2PDMA_MAP_UNKNOWN)
> ret = upstream_bridge_map_type_warn(provider, client, NULL,
> GFP_ATOMIC);
>
> return ret;
>
>
>> }
>> static int __pci_p2pdma_map_sg(struct pci_p2pdma_pagemap *p2p_pgmap,
>> @@ -877,7 +884,6 @@ int pci_p2pdma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
>> case PCI_P2PDMA_MAP_BUS_ADDR:
>> return __pci_p2pdma_map_sg(p2p_pgmap, dev, sg, nents);
>> default:
>> - WARN_ON_ONCE(1);
>
> Why? Or at least, why, in this patch? It looks like an accidental
> leftover from something, seeing as how it is not directly related to the
> patch, and is not mentioned at all.
>
>
> thanks,
next prev parent reply other threads:[~2021-05-11 16:06 UTC|newest]
Thread overview: 99+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-08 17:01 [PATCH 00/16] Add new DMA mapping operation for P2PDMA Logan Gunthorpe
2021-04-08 17:01 ` [PATCH 01/16] PCI/P2PDMA: Pass gfp_mask flags to upstream_bridge_distance_warn() Logan Gunthorpe
2021-05-02 3:58 ` John Hubbard
2021-05-03 15:57 ` Logan Gunthorpe
2021-05-03 18:17 ` John Hubbard
2021-05-03 18:20 ` Logan Gunthorpe
2021-05-03 18:23 ` John Hubbard
2021-05-03 18:24 ` Christoph Hellwig
2021-05-11 16:05 ` Don Dutile
2021-05-11 16:12 ` Logan Gunthorpe
2021-05-11 16:23 ` Don Dutile
2021-04-08 17:01 ` [PATCH 02/16] PCI/P2PDMA: Avoid pci_get_slot() which sleeps Logan Gunthorpe
2021-05-02 5:35 ` John Hubbard
2021-05-03 16:08 ` Logan Gunthorpe
2021-05-03 18:20 ` John Hubbard
2021-05-03 18:25 ` Christoph Hellwig
2021-05-11 16:05 ` Don Dutile
2021-05-11 16:16 ` Logan Gunthorpe
2021-05-11 16:05 ` Don Dutile
2021-05-11 16:14 ` Logan Gunthorpe
2021-04-08 17:01 ` [PATCH 03/16] PCI/P2PDMA: Attempt to set map_type if it has not been set Logan Gunthorpe
2021-05-02 19:58 ` John Hubbard
2021-05-03 16:17 ` Logan Gunthorpe
2021-05-03 18:22 ` John Hubbard
2021-05-03 18:35 ` Christoph Hellwig
2021-05-03 18:46 ` Logan Gunthorpe
2021-05-11 16:05 ` Don Dutile [this message]
2021-04-08 17:01 ` [PATCH 04/16] PCI/P2PDMA: Refactor pci_p2pdma_map_type() to take pagmap and device Logan Gunthorpe
2021-05-02 20:41 ` John Hubbard
2021-05-03 16:30 ` Logan Gunthorpe
2021-05-03 18:31 ` John Hubbard
2021-05-03 18:56 ` Logan Gunthorpe
2021-05-03 21:54 ` John Hubbard
2021-05-03 22:57 ` Jason Gunthorpe
2021-05-03 23:40 ` John Hubbard
2021-04-08 17:01 ` [PATCH 05/16] dma-mapping: Introduce dma_map_sg_p2pdma() Logan Gunthorpe
2021-04-27 19:22 ` Jason Gunthorpe
2021-04-27 22:49 ` Logan Gunthorpe
2021-04-27 19:31 ` Jason Gunthorpe
2021-04-27 22:55 ` Logan Gunthorpe
2021-04-27 23:01 ` Jason Gunthorpe
2021-05-03 18:28 ` Christoph Hellwig
2021-05-03 18:31 ` Logan Gunthorpe
2021-05-02 21:23 ` John Hubbard
2021-05-03 16:38 ` Logan Gunthorpe
2021-05-11 16:05 ` Don Dutile
2021-04-08 17:01 ` [PATCH 06/16] lib/scatterlist: Add flag for indicating P2PDMA segments in an SGL Logan Gunthorpe
2021-05-02 22:34 ` John Hubbard
2021-04-08 17:01 ` [PATCH 07/16] PCI/P2PDMA: Make pci_p2pdma_map_type() non-static Logan Gunthorpe
2021-05-02 22:44 ` John Hubbard
2021-05-03 16:39 ` Logan Gunthorpe
2021-05-11 16:06 ` Don Dutile
2021-05-11 16:17 ` Logan Gunthorpe
2021-04-08 17:01 ` [PATCH 08/16] PCI/P2PDMA: Introduce helpers for dma_map_sg implementations Logan Gunthorpe
2021-05-02 22:52 ` John Hubbard
2021-05-03 0:50 ` John Hubbard
2021-05-03 17:15 ` Logan Gunthorpe
2021-04-08 17:01 ` [PATCH 09/16] dma-direct: Support PCI P2PDMA pages in dma-direct map_sg Logan Gunthorpe
2021-04-27 19:33 ` Jason Gunthorpe
2021-04-27 19:40 ` Jason Gunthorpe
2021-04-27 22:56 ` Logan Gunthorpe
2021-05-02 23:28 ` John Hubbard
2021-05-02 23:32 ` John Hubbard
2021-05-03 17:06 ` Logan Gunthorpe
2021-05-03 16:55 ` Logan Gunthorpe
2021-05-04 0:12 ` John Hubbard
2021-05-03 17:04 ` Logan Gunthorpe
2021-05-04 0:01 ` John Hubbard
2021-04-08 17:01 ` [PATCH 10/16] dma-mapping: Add flags to dma_map_ops to indicate PCI P2PDMA support Logan Gunthorpe
2021-05-03 0:32 ` John Hubbard
2021-05-03 17:09 ` Logan Gunthorpe
2021-05-11 16:06 ` Don Dutile
2021-05-11 16:19 ` Logan Gunthorpe
2021-04-08 17:01 ` [PATCH 11/16] iommu/dma: Support PCI P2PDMA pages in dma-iommu map_sg Logan Gunthorpe
2021-04-27 19:43 ` Jason Gunthorpe
2021-04-27 22:59 ` Logan Gunthorpe
2021-05-03 1:14 ` John Hubbard
2021-05-06 23:59 ` Logan Gunthorpe
2021-05-11 16:06 ` Don Dutile
2021-05-11 16:35 ` Logan Gunthorpe
2021-04-08 17:01 ` [PATCH 12/16] nvme-pci: Check DMA ops when indicating support for PCI P2PDMA Logan Gunthorpe
2021-05-03 1:29 ` John Hubbard
2021-05-03 17:17 ` Logan Gunthorpe
2021-05-04 0:17 ` John Hubbard
2021-04-08 17:01 ` [PATCH 13/16] nvme-pci: Convert to using dma_map_sg_p2pdma for p2pdma pages Logan Gunthorpe
2021-05-03 1:34 ` John Hubbard
2021-05-03 17:19 ` Logan Gunthorpe
2021-05-04 0:26 ` John Hubbard
2021-04-08 17:01 ` [PATCH 14/16] nvme-rdma: Ensure dma support when using p2pdma Logan Gunthorpe
2021-04-27 19:47 ` Jason Gunthorpe
2021-04-27 22:59 ` Logan Gunthorpe
2021-05-03 1:37 ` John Hubbard
2021-04-08 17:01 ` [PATCH 15/16] RDMA/rw: use dma_map_sg_p2pdma() Logan Gunthorpe
2021-04-08 17:01 ` [PATCH 16/16] PCI/P2PDMA: Remove pci_p2pdma_[un]map_sg() Logan Gunthorpe
2021-04-27 19:28 ` [PATCH 00/16] Add new DMA mapping operation for P2PDMA Jason Gunthorpe
2021-04-27 20:21 ` John Hubbard
2021-04-27 20:48 ` Dan Williams
2021-05-02 1:22 ` John Hubbard
2021-05-11 16:05 ` Don Dutile
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