linux-kernel - Re: [PATCH v2] xen: add new hypercall buffer mapping device

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Date:   Mon, 18 Jun 2018 11:27:05 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Juergen Gross <jgross@...e.com>, linux-kernel@...r.kernel.org,
        xen-devel@...ts.xenproject.org
Subject: Re: [PATCH v2] xen: add new hypercall buffer mapping device

On 06/18/2018 03:36 AM, Juergen Gross wrote:
> For passing arbitrary data from user land to the Xen hypervisor the
> Xen tools today are using mlock()ed buffers. Unfortunately the kernel
> might change access rights of such buffers for brief periods of time
> e.g. for page migration or compaction, leading to access faults in the
> hypervisor, as the hypervisor can't use the locks of the kernel.
>
> In order to solve this problem add a new device node to the Xen privcmd
> driver to easily allocate hypercall buffers via mmap(). The memory is
> allocated in the kernel and just mapped into user space. Marked as
> VM_IO the user mapping will not be subject to page migration et al.
>
> Signed-off-by: Juergen Gross <jgross@...e.com>


Reviewed-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>