linux-kernel - Re: [RFC] /dev/ioasid uAPI proposal

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Date:   Wed, 2 Jun 2021 16:54:26 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     "Tian, Kevin" <kevin.tian@...el.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Liu Yi L <yi.l.liu@...ux.intel.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        Jonathan Corbet <corbet@....net>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "Alex Williamson (alex.williamson@...hat.com)\"\"" 
        <alex.williamson@...hat.com>, David Woodhouse <dwmw2@...radead.org>
Subject: Re: [RFC] /dev/ioasid uAPI proposal


在 2021/6/2 上午1:31, Jason Gunthorpe 写道:
> On Tue, Jun 01, 2021 at 04:47:15PM +0800, Jason Wang wrote:
>   
>> We can open up to ~0U file descriptors, I don't see why we need to restrict
>> it in uAPI.
> There are significant problems with such large file descriptor
> tables. High FD numbers man things like select don't work at all
> anymore and IIRC there are more complications.


I don't see how much difference for IOASID and other type of fds. People 
can choose to use poll or epoll.

And with the current proposal, (assuming there's a N:1 ioasid to 
ioasid). I wonder how select can work for the specific ioasid.

Thanks


>
> A huge number of FDs for typical usages should be avoided.
>
> Jason
>