Subject: Re: [PATCH 1/2] vhost: add ioctl to query nregions upper limit
To: "Michael S. Tsirkin" <mst@redhat.com>, Igor Mammedov <imammedo@redhat.com>
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Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org
From: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <55B8EAD7.70809@redhat.com>
Date: Wed, 29 Jul 2015 17:01:43 +0200
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On 29/07/2015 16:56, Michael S. Tsirkin wrote:
>>>> > > > Also, document our contract with legacy userspace: when running on an
>>>> > > > old kernel, you get -1 and you can assume at least 64 slots.  Since 0
>>>> > > > value's left unused, let's make that mean that the current userspace
>>>> > > > behaviour (trial and error) is required, just in case we want it back.
>>> > > 
>>> > > What's wrong with reading the module parameter value? It's there in
>>> > > sysfs ...
>> > for most cases it would work but distro doesn't have to mount
>> > sysfs under /sys
> If it wants to rewrite all userspace, sure it doesn't.

I agree, on the other hand it doesn't seem far fetched to have a per-fd
maximum in the future.  So I think this patch is more future-proof.

Paolo
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