Re: [PATCH 2/3] xen/privcmd: Add IOCTL_PRIVCMD_DM_OP

From: Boris Ostrovsky
Date: Thu Feb 09 2017 - 10:50:20 EST

On 02/09/2017 09:27 AM, Paul Durrant wrote:
-----Original Message-----
From: Paul Durrant [mailto:paul.durrant@xxxxxxxxxx]
Sent: 09 February 2017 14:18
To: xen-devel@xxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
Cc: Paul Durrant <Paul.Durrant@xxxxxxxxxx>; Boris Ostrovsky
<boris.ostrovsky@xxxxxxxxxx>; Juergen Gross <jgross@xxxxxxxx>
Subject: [PATCH 2/3] xen/privcmd: Add IOCTL_PRIVCMD_DM_OP

Recently a new dm_op[1] hypercall was added to Xen to provide a
for restricting device emulators (such as QEMU) to a limited set of
hypervisor operations, and being able to audit those operations in the
kernel of the domain in which they run.

This patch adds IOCTL_PRIVCMD_DM_OP as gateway for
bouncing the callers buffers through kernel memory to allow the address
ranges to be audited (and negating the need to bounce through locked
memory in user-space).

Actually, it strikes me (now that I've posted the patch) that I should probably just mlock the user buffers rather than bouncing them through kernel... Anyway, I'd still appreciate review on other aspects of the patch.

Are you suggesting that the caller (user) mlocks the buffers?