netdev - Re: [Patch v8 12/12] RDMA/mana_ib: Add a driver for Microsoft Azure Network Adapter

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Date:   Fri, 21 Oct 2022 20:34:51 -0400
From:   Tom Talpey <tom@...pey.com>
To:     Long Li <longli@...rosoft.com>,
        Bernard Metzler <BMT@...ich.ibm.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Leon Romanovsky <leon@...nel.org>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "shiraz.saleem@...el.com" <shiraz.saleem@...el.com>,
        Ajay Sharma <sharmaajay@...rosoft.com>
Cc:     "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>
Subject: Re: [Patch v8 12/12] RDMA/mana_ib: Add a driver for Microsoft Azure
 Network Adapter

On 10/21/2022 6:55 PM, Long Li wrote:
>>> The upper 8 bits of an ib_mr remote token are reserved for use as a
>>> rotating key, this allows a consumer to more safely reuse an ib_mr
>>> without having to overallocate large region pools.
>>>
>>> Tom.
>>
>> Right, my point was that one cannot encode INT_MAX different MR
>> identifiers into 32 - 8 = 24 bits.
>>
>> Best,
>> Bernard.
> 
> The hardware exposes the number of MRs that exceeds UINT32_MAX.
> There is no software stack limit from hardware perspective.
> 
> In this case, maybe it's a good idea to set it to 0xFFFFFF. I'm making the change.

Actually, 2^24 MRs is enormous in itself. Does this driver
actually support that many? Without falling over?

Tom.