linux-kernel - Re: [PATCH rdma-next 01/10] RDMA: Add access flags to ib_alloc_mr() and ib_mr_pool

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Message-ID: <20210406141552.GA4936@lst.de>
Date:   Tue, 6 Apr 2021 16:15:52 +0200
From:   Christoph Hellwig <hch@....de>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     Christoph Hellwig <hch@....de>, Leon Romanovsky <leon@...nel.org>,
        Bart Van Assche <bvanassche@....org>,
        Doug Ledford <dledford@...hat.com>,
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        Weihang Li <liweihang@...wei.com>,
        Yishai Hadas <yishaih@...dia.com>,
        Zhu Yanjun <zyjzyj2000@...il.com>
Subject: Re: [PATCH rdma-next 01/10] RDMA: Add access flags to
 ib_alloc_mr() and ib_mr_pool_init()

On Tue, Apr 06, 2021 at 11:04:37AM -0300, Jason Gunthorpe wrote:
> It might be idiodic, but I have to keep the uverbs thing working
> too.
> 
> There is a lot of assumption baked in to all the drivers that
> user/kernel is the same thing, we'd have to go in and break this.
> 
> Essentially #2 ends up as deleting IB_ACCESS_RELAXED_ORDERING kernel
> side and instead doing some IB_ACCESS_DISABLE_RO in kernel,
> translating uverbs IBV_ACCESS_* to this then finding and inverting all
> the driver logic and also finding and unblocking all the places that
> enforce valid access flags in the drivers. It is complicated enough

Inverting the polarity of a flag at the uapi boundary is pretty
trivial and we already do it all over the kernel.

Do we actually ever need the strict ordering semantics in the kernel?