Re: [Qemu-devel] [PATCH v4 0/7] q35: add negotiable broadcast SMI

[Laszlo Ersek <lersek@redhat.com>]

On 01/10/17 17:05, Michael S. Tsirkin wrote:
> On Tue, Jan 10, 2017 at 04:23:41PM +0100, Laszlo Ersek wrote:
>> On 01/10/17 16:06, Michael S. Tsirkin wrote:
>>> On Thu, Dec 01, 2016 at 06:06:17PM +0100, Laszlo Ersek wrote:
>>>> * This is version 4 of the series; the last version was at
>>>>   <http://lists.nongnu.org/archive/html/qemu-devel/2016-11/msg03582.html>.
>>>>
>>>>   This version is practically a rewrite from scratch, seeking to address
>>>>   the v3 feedback. Here's what the individual patches do:
>>>>
>>>>   - Patch #1 rebases and extends Michael's "writeable fw_cfg blobs"
>>>>     patch from Feb/March 2016. The changes relative to the original
>>>>     patch are documented in the commit message (the code changes are
>>>>     minimal).
>>>>
>>>>   - Patches #2 and #3 turn the FW_CFG_FILE_SLOTS constant into a device
>>>>     property, and expose the desired number of fw_cfg file slots to
>>>>     board code. This is meant to address a concern raised by Paolo in
>>>>     the v2 review
>>>>     <http://lists.nongnu.org/archive/html/qemu-devel/2016-11/msg03125.html>,
>>>>     namely that we're about to run out of FW_CFG_FILE_SLOTS.
>>>>
>>>>   - Patch #4 introduces the "pc-q35-2.9" and "pc-i440fx-2.9" machine
>>>>     types, which are allowed to take advantage of the new default for
>>>>     fw_cfg file slots (0x20 rather than 0x10).
>>>>
>>>>   - Patch #5 introduces SMI feature negotiation via fw_cfg, with the
>>>>     following new files:
>>>>
>>>>     - etc/smi/host-features
>>>>     - etc/smi/guest-features
>>>>     - etc/smi/features-ok
>>>>
>>>>     This is supposed to follow Michael's recommendation re: imitating
>>>>     virtio
>>>>     <http://lists.nongnu.org/archive/html/qemu-devel/2016-11/msg03218.html>.
>>>>
>>>>     The guest-features file is freely writeable by the guest (no write
>>>>     callbacks in fw_cfg), and the feature validation & lockdown occurs
>>>>     when the guest selects the features-ok file (for reading).
>>>>
>>>>     Board code is allowed to choose the host feature bitmap to
>>>>     advertise.
>>>>
>>>>     This patch doesn't add any specific SMI features yet.
>>>>
>>>>   - Patch #6 adds the ICH9_LPC_SMI_F_BROADCAST feature.
>>>>
>>>>   - Patch #7 introduces the PCMachineClass.get_smi_host_features method,
>>>>     and implements it for "pc-q35-2.9" and later. The idea is to tie the
>>>>     SMI host features to machine types, and let the machine types
>>>>     calculate their host features with code (i.e., not just a constant).
>>>>
>>>>     In this patch, the "pc-q35-2.9" machine type exposes the
>>>>     ICH9_LPC_SMI_F_BROADCAST feature iff (smp_cpus == max_cpus), that
>>>>     is, when VCPU hotplug is not possible. (Also from Paolo's v3
>>>>     feedback, in
>>>>     <http://lists.nongnu.org/archive/html/qemu-devel/2016-11/msg04919.html>.)
>>>>
>>>> * I've written the OVMF side patches too and tested them together
>>>>   (including gdb / debug messages for "white box" testing).
>>>>
>>>> * Note that this version depends on the following PULL req from Michael:
>>>>
>>>>   [Qemu-devel] [PULL 0/5] virtio, vhost, pc: fixes
>>>>   http://lists.nongnu.org/archive/html/qemu-devel/2016-11/msg05503.html
>>>>
>>>>   In particular on the following patch:
>>>>   "loader: fix handling of custom address spaces when adding ROM blobs"
>>>>
>>>> Cc: "Gabriel L. Somlo" <somlo@cmu.edu>
>>>> Cc: "Michael S. Tsirkin" <mst@redhat.com>
>>>> Cc: Eduardo Habkost <ehabkost@redhat.com>
>>>> Cc: Gerd Hoffmann <kraxel@redhat.com>
>>>> Cc: Igor Mammedov <imammedo@redhat.com>
>>>> Cc: Michael Walle <michael@walle.cc>
>>>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>>>> Cc: Peter Maydell <peter.maydell@linaro.org>
>>>> Cc: Shannon Zhao <zhaoshenglong@huawei.com>
>>>> Cc: qemu-arm@nongnu.org
>>>>
>>>> Thanks
>>>> Laszlo
>>>
>>> So I reviewed fw cfg stuff, looks good to me.
>>
>> Thank you.
>>
>> I should note that Igor suggested / requested changes for patches #2 and
>> #3; the sub-threads start at
>>
>> http://lists.nongnu.org/archive/html/qemu-devel/2016-12/msg00695.html
>> msg-id: <20161206115038.4495a217@nial.brq.redhat.com>
>>
>> http://lists.nongnu.org/archive/html/qemu-devel/2016-12/msg00706.html
>> msg-id: <20161206124906.76a41896@nial.brq.redhat.com>
>>
>> I was about to rework the patches based on his feedback. Should we
>> resume those discussions?
> 
> If you both agree, pls go ahead and make these changes.

Okay, will do.

> 
>>> I'd prefer Paolo to review
>>> and merge broadcast SMI stuff as appropriate.  Paolo, makes sense?
>>
>> If it helps, I can split the series into two "waves", and deal only with
>> fw_cfg first.
>>
>> Thanks!
>> Laszlo
> 
> I don't mind either way.

I'll see then how I feel about splitting v5 when I'm ready to post it. :)

Thanks!
Laszlo