From: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
To: Ian Campbell <Ian.Campbell@eu.citrix.com>
Cc: "ddutile@redhat.com" <ddutile@redhat.com>,
Stefano Stabellini <Stefano.Stabellini@eu.citrix.com>,
"jeremy@goop.org" <jeremy@goop.org>,
"xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
"stefano@stabellini.net" <stefano@stabellini.net>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"sheng@linux.intel.com" <sheng@linux.intel.com>
Subject: Re: [Xen-devel] Re: [PATCH 12/13] Unplug emulated disks and nics
Date: Fri, 9 Jul 2010 11:54:24 +0100 [thread overview]
Message-ID: <alpine.DEB.2.00.1007091150000.21432@kaball-desktop> (raw)
In-Reply-To: <1278662546.28432.602.camel@zakaz.uk.xensource.com>
On Fri, 9 Jul 2010, Ian Campbell wrote:
> >
> > > Any guest which uses xvda in its configuration file today will be using
> > > emulated devices but I think that with Stefano's patch and your proposed
> > > change in default on a Xen system without support for unplug will start
> > > using PV devices without unplugging the emulated ones first.
> > >
> > Well, Stefano requires the admin to add unplug switch to kernel cmd line,
>
> In the case where the host platform does not support the unplug protocol
> this is correct and requiring explicit admin action to allow the PV
> frontends to activate is the only safe option WRT the users data.
>
> However if the host platform does support the unplug protocol then this
> is incorrect. In that case the default (in the absence of the command
> line option) is to automatically unplug any device for which a PV driver
> is available and so no command line option will be required in the
> common case. (see xen_unplug_emulated_devices() under the comment "Set
> the default value of xen_emul_unplug depending on...")
>
that's right: on host platforms supporting unplug no command line options
are required; on the other hand if the host platform does not support
unplug then xen_emul_unplug=ignore is required to use PV drivers anyway.
> > so I don't see the harm in defaulting to unplug...
>
> As I described in my previous mail this is unsafe on host platforms
> which do not support unplug. As I describe above it is unnecessary on
> host platforms which do support unplug
>
yep, keep in mind the copy and paste example.
If you are happy about the patch, I'll include it in my next version.
WARNING: multiple messages have this Message-ID (diff)
From: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
To: Ian Campbell <Ian.Campbell@eu.citrix.com>
Cc: "jeremy@goop.org" <jeremy@goop.org>,
"xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
Stefano Stabellini <Stefano.Stabellini@eu.citrix.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"stefano@stabellini.net" <stefano@stabellini.net>,
"ddutile@redhat.com" <ddutile@redhat.com>,
"sheng@linux.intel.com" <sheng@linux.intel.com>
Subject: Re: Re: [PATCH 12/13] Unplug emulated disks and nics
Date: Fri, 9 Jul 2010 11:54:24 +0100 [thread overview]
Message-ID: <alpine.DEB.2.00.1007091150000.21432@kaball-desktop> (raw)
In-Reply-To: <1278662546.28432.602.camel@zakaz.uk.xensource.com>
On Fri, 9 Jul 2010, Ian Campbell wrote:
> >
> > > Any guest which uses xvda in its configuration file today will be using
> > > emulated devices but I think that with Stefano's patch and your proposed
> > > change in default on a Xen system without support for unplug will start
> > > using PV devices without unplugging the emulated ones first.
> > >
> > Well, Stefano requires the admin to add unplug switch to kernel cmd line,
>
> In the case where the host platform does not support the unplug protocol
> this is correct and requiring explicit admin action to allow the PV
> frontends to activate is the only safe option WRT the users data.
>
> However if the host platform does support the unplug protocol then this
> is incorrect. In that case the default (in the absence of the command
> line option) is to automatically unplug any device for which a PV driver
> is available and so no command line option will be required in the
> common case. (see xen_unplug_emulated_devices() under the comment "Set
> the default value of xen_emul_unplug depending on...")
>
that's right: on host platforms supporting unplug no command line options
are required; on the other hand if the host platform does not support
unplug then xen_emul_unplug=ignore is required to use PV drivers anyway.
> > so I don't see the harm in defaulting to unplug...
>
> As I described in my previous mail this is unsafe on host platforms
> which do not support unplug. As I describe above it is unnecessary on
> host platforms which do support unplug
>
yep, keep in mind the copy and paste example.
If you are happy about the patch, I'll include it in my next version.
next prev parent reply other threads:[~2010-07-09 10:54 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-21 16:12 [PATCH 0/12] PV on HVM Xen Stefano Stabellini
2010-06-21 16:12 ` Stefano Stabellini
2010-06-21 16:13 ` [PATCH 01/13] Add support for hvm_op stefano
2010-06-21 16:13 ` [PATCH 02/13] early PV on HVM stefano
2010-06-21 16:13 ` [PATCH 03/13] evtchn delivery " stefano
2010-06-21 16:13 ` [PATCH 04/13] Xen PCI platform device driver stefano
2010-06-30 17:55 ` Konrad Rzeszutek Wilk
2010-06-30 17:55 ` Konrad Rzeszutek Wilk
2010-07-01 11:38 ` Stefano Stabellini
2010-06-21 16:13 ` [PATCH 05/13] Add suspend\resume support for PV on HVM guests stefano
2010-06-21 16:14 ` [PATCH 06/13] Allow xen platform pci device to be compiled as a module stefano
2010-06-21 16:14 ` [PATCH 0/12] PV on HVM Xen Stefano Stabellini
2010-06-21 16:14 ` Stefano Stabellini
2010-06-21 16:14 ` [PATCH 07/13] Fix find_unbound_irq in presence of ioapic irqs stefano
2010-06-21 16:14 ` [PATCH 08/13] Fix possible NULL pointer dereference in print_IO_APIC stefano
2010-06-21 16:14 ` [PATCH 09/13] __setup_vector_irq: handle NULL chip_data stefano
2010-06-21 16:14 ` [PATCH 10/13] Do not try to disable hpet if it hasn't been initialized before stefano
2010-06-30 17:53 ` Konrad Rzeszutek Wilk
2010-06-30 17:53 ` Konrad Rzeszutek Wilk
2010-07-09 1:05 ` john stultz
2010-06-30 21:24 ` Venkatesh Pallipadi
2010-06-30 21:24 ` Venkatesh Pallipadi
2010-07-02 10:44 ` Paolo Bonzini
2010-07-02 10:44 ` Paolo Bonzini
2010-06-21 16:14 ` [PATCH 11/13] Use xen_vcpuop_clockevent, xen_clocksource and xen wallclock stefano
2010-07-01 19:41 ` Don Dutile
2010-07-02 17:17 ` Stefano Stabellini
2010-07-02 17:17 ` Stefano Stabellini
2010-06-21 16:14 ` [PATCH 12/13] Unplug emulated disks and nics stefano
2010-07-01 19:41 ` Don Dutile
2010-07-01 19:41 ` Don Dutile
2010-07-05 11:58 ` Stefano Stabellini
2010-07-07 20:01 ` Don Dutile
2010-07-08 13:13 ` Stefano Stabellini
2010-07-08 13:13 ` Stefano Stabellini
2010-07-08 19:57 ` [Xen-devel] " Don Dutile
2010-07-08 21:29 ` Ian Campbell
2010-07-08 21:29 ` Ian Campbell
2010-07-08 21:59 ` [Xen-devel] " Don Dutile
2010-07-09 8:02 ` Ian Campbell
2010-07-09 8:02 ` Ian Campbell
2010-07-09 10:54 ` Stefano Stabellini [this message]
2010-07-09 10:54 ` Stefano Stabellini
2010-07-09 13:42 ` [Xen-devel] " Don Dutile
2010-06-21 16:14 ` [PATCH 13/13] Call HVMOP_pagetable_dying on exit_mmap stefano
2010-06-30 17:56 ` [PATCH 0/12] PV on HVM Xen Konrad Rzeszutek Wilk
2010-07-01 11:38 ` Stefano Stabellini
2010-07-01 19:43 ` [Xen-devel] " Dan Magenheimer
2010-07-02 10:43 ` Stefano Stabellini
2010-07-02 16:08 ` Dan Magenheimer
2010-07-02 17:14 ` Stefano Stabellini
2010-07-02 19:49 ` Dan Magenheimer
2010-07-02 19:49 ` Dan Magenheimer
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