From: kbusch@kernel.org (Keith Busch)
Subject: Controller memory buffer - P2PDMA question
Date: Tue, 23 Apr 2019 12:02:29 -0600 [thread overview]
Message-ID: <20190423180228.GA15382@localhost.localdomain> (raw)
In-Reply-To: <5979444b-1fbf-3471-ceb0-d90c705c40d7@intel.com>
On Tue, Apr 23, 2019@11:55:03AM -0600, Heitke, Kenneth wrote:
> For the controller memory buffer, the read-data (RDS) and write-data (WDS)
> support isn't required to symmetrical since there are individual bits for
> each. The code below requires that both be supported before the P2P memory
> will be published
>
> nvme_map_cmb:nvme/host/pci.c
>
> if ((dev->cmbsz & (NVME_CMBSZ_WDS | NVME_CMBSZ_RDS)) ==
> (NVME_CMBSZ_WDS | NVME_CMBSZ_RDS))
> pci_p2pmem_publish(pdev, true);
>
> Would it make sense for P2PDMA to support the idea of directionality? Should
> a device be able to publish its controller memory buffer just for TO_DEVICE
> and/or FROM_DEVICE?
P2P needs both directions for registered device memory. It
indiscriminately selects peer destinations, which are later used as
sources.
next prev parent reply other threads:[~2019-04-23 18:02 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-23 17:55 Controller memory buffer - P2PDMA question Heitke, Kenneth
2019-04-23 18:02 ` Keith Busch [this message]
2019-04-23 18:24 ` Logan Gunthorpe
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