linux-kernel - Re: [PATCH v3 00/14] Adding GAUDI NIC code to habanalabs driver

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Message-ID: <20200918150735.GV8409@ziepe.ca>
Date:   Fri, 18 Sep 2020 12:07:35 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Oded Gabbay <oded.gabbay@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>, izur@...ana.ai,
        Gal Pressman <galpress@...zon.com>,
        Jakub Kicinski <kuba@...nel.org>,
        "Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
        netdev@...r.kernel.org, SW_Drivers <SW_Drivers@...ana.ai>,
        "David S. Miller" <davem@...emloft.net>,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        linux-rdma@...r.kernel.org, Olof Johansson <olof@...om.net>
Subject: Re: [PATCH v3 00/14] Adding GAUDI NIC code to habanalabs driver

On Fri, Sep 18, 2020 at 05:45:21PM +0300, Oded Gabbay wrote:

> Any access by the device's engines to the host memory is done via our
> device's MMU. Our MMU supports multiple ASIDs - Address Space IDs. The
> kernel driver is assigned ASID 0, while the user is assigned ASID 1.
> We can support up to 1024 ASIDs, but because we limit the user to have
> a single application, we only use ASID 0 and 1.

If the QP/WQ/etc is HW bound to an ASID then that binding is called a
PD and the ASID is acting in the PD role.

If the ASID is translating from on the wire IOVA to DMA PA, then it is
acting in the MR role as well.

Bundling those two things together is not as flexible as standards
based RDMA, but it is not as far away as you are making things out to
be.

Jason