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

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Date:   Sat, 22 Oct 2022 00:38:35 +0000
From:   Long Li <longli@...rosoft.com>
To:     tom <tom@...pey.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

> 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.

The hardware can support that much. I don't see this driver will enforce other
limitation on that.