[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] [RFC PATCH 4/6] vm_event: Use slotted channels for sync requests.

Hi Paul,

On 12/20/18 2:28 PM, Paul Durrant wrote:
-----Original Message-----
From: Petre Ovidiu PIRCALABU [mailto:ppircalabu@xxxxxxxxxxxxxxx]
Sent: 20 December 2018 14:26
To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>; Wei Liu
<wei.liu2@xxxxxxxxxx>; Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>; Konrad
Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>; George Dunlap
<George.Dunlap@xxxxxxxxxx>; Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>; Ian
Jackson <Ian.Jackson@xxxxxxxxxx>; Tim (Xen.org) <tim@xxxxxxx>; Julien
Grall <julien.grall@xxxxxxx>; Tamas K Lengyel <tamas@xxxxxxxxxxxxx>; Jan
Beulich <jbeulich@xxxxxxxx>; Roger Pau Monne <roger.pau@xxxxxxxxxx>
Subject: Re: [Xen-devel] [RFC PATCH 4/6] vm_event: Use slotted channels
for sync requests.

On Thu, 2018-12-20 at 12:05 +0000, Paul Durrant wrote:
The memory for the asynchronous ring and the synchronous channels
be allocated from domheap and mapped to the controlling domain
using the
foreignmemory_map_resource interface. Unlike the current
the allocated pages are not part of the target DomU, so they will
not be
reclaimed when the vm_event domain is disabled.

Why re-invent the wheel here? The ioreq infrastructure already does
pretty much everything you need AFAICT.


I wanted preseve as much as possible from the existing vm_event DOMCTL
interface and add only the necessary code to allocate and map the

That means we have two subsystems duplicating a lot of functionality though. It 
would be much better to use ioreq server if possible than provide a 
compatibility interface via DOMCTL.

Also, to my knowledge, the ioreq server is only supported for x86 hvm
targets. I didn't want to add an extra limitation to the vm_event

I believe Julien is already porting it to ARM.

FWIW, yes I have a port of ioreq for Arm. Still cleaning-up the code.


Julien Grall

Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.