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From: Juergen Gross <>
To: Jan Beulich <>
Subject: Re: [Xen-devel] [PATCH] xen: remove size limit of privcmd-buf mapping interface
Date: Thu, 1 Nov 2018 15:23:09 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On 01/11/2018 15:18, Jan Beulich wrote:
>>>> Juergen Gross <> 11/01/18 1:34 PM >>>
>> Currently the size of hypercall buffers allocated via
>> /dev/xen/hypercall is limited to a default of 64 memory pages. For live
>> migration of guests this might be too small as the page dirty bitmask
>> needs to be sized according to the size of the guest. This means
>> migrating a 8GB sized guest is already exhausting the default buffer
>> size for the dirty bitmap.
>> There is no sensible way to set a sane limit, so just remove it
>> completely. The device node's usage is limited to root anyway, so there
>> is no additional DOS scenario added by allowing unlimited buffers.
> But is this setting of permissions what we want long term? What about a
> de-privileged qemu, which still needs to be able to issue at least dm-op
> hypercalls?

Wouldn't that qemu have opened the node while still being privileged?


  reply	other threads:[~2018-11-01 14:23 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-01 12:33 Juergen Gross
2018-11-01 14:18 ` [Xen-devel] " Jan Beulich
2018-11-01 14:23   ` Juergen Gross [this message]
2018-11-01 15:50     ` Jan Beulich
     [not found]     ` <>
2018-11-01 16:27       ` Juergen Gross
2018-11-02  7:26         ` Jan Beulich
2018-11-01 14:23   ` Andrew Cooper
2018-11-09  7:03 ` Juergen Gross
2018-11-09 14:23   ` Boris Ostrovsky
2018-11-02  9:53 [Xen-devel] " Juergen Gross

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