On Mon, 1 Apr 2019 12:01:48 -0300
"Maxiwell S. Garcia" <address@hidden> wrote:
Hi Greg,
Thanks for your review. I added some comments below...
On Fri, Mar 29, 2019 at 01:29:51PM +0100, Greg Kurz wrote:
On Thu, 28 Mar 2019 15:39:45 -0300
"Maxiwell S. Garcia" <address@hidden> wrote:
Hi,
On Thu, Mar 28, 2019 at 02:21:51PM +0100, Greg Kurz wrote:
On Wed, 27 Mar 2019 17:41:00 -0300
"Maxiwell S. Garcia" <address@hidden> wrote:
Here are two patches to add a handler for ibm,get-vpd RTAS calls.
This RTAS exposes host information in case of set QEMU options
'host-serial' and 'host-model' as 'passthrough'.
The patch 1 creates helper functions to get valid 'host-serial'
and 'host-model' parameters, guided by QEMU command line. These
parameters are useful to build the guest device tree and to return
get-vpd RTAS calls. The patch 2 adds the ibm,get-vpd itself.
Update v7:
* rtas_get_vpd_fields as a static array in spapr machine state
Maxiwell S. Garcia (2):
spapr: helper functions to get valid host fields
spapr-rtas: add ibm,get-vpd RTAS interface
hw/ppc/spapr.c | 48 +++++++++++----------
hw/ppc/spapr_rtas.c | 96 ++++++++++++++++++++++++++++++++++++++++++
include/hw/ppc/spapr.h | 14 +++++-
3 files changed, 135 insertions(+), 23 deletions(-)
Hi Maxiwell,
David sent a patch to rework how the host data is exposed to the guest.
Especially, the special casing of the "none" and "passthrough" strings
is no more... I'm afraid you'll have to rework your patches accordingly:
code+changelog in patch 1 and at least changelog in patch 2.
Cheers,
IIUC, the 'ibm,get-vpd' RTAS should return information about the
platform/cabinet. Thus, it's not necessary to add new nodes in the guest
device tree to export information like that.
I agree that these "host-model" and "host-serial" props, which aren't
described anywhere and not used by either the linux kernel or the
powerpc-utils, look like a QEMU-specific poor man's version of VPD.
Not quite sure why they were even created since this is the purpose
of "system-id" and "model" as explained in PAPR, and supposedly
exposed in /proc/ppc64/lparcfg according to the LPARCFG(5) manual
page:
serial_number
The serial number of the physical system in which the partition resides
system_type
The machine,type-model of the physical system in which the partition
resides
This is indeed what we get in a PowerVM LPAR running on a tuleta system:
address@hidden ~]# head -3 /proc/ppc64/lparcfg
lparcfg 1.9
serial_number=IBM,032116A9A
system_type=IBM,8247-22L
address@hidden ~]# echo $(cat /proc/device-tree/system-id)
IBM,032116A9A
address@hidden ~]# echo $(cat /proc/device-tree/model)
IBM,8247-22L
But QEMU generates a hard coded "IBM pSeries (emulated by qemu)" model,
which is clearly not PAPR compliant according to this requirement:
R1–12.2–13. There must be a property, “model”, under the root node
in the format, “<vendor>,xxxx-yyy”, where <vendor> is replaced by
one to five letters representing the stock symbol of the company
(for example, for IBM: “IBM,xxxx-yyy”), and where xxxx-yyy is
derived from the VPD TM field (see Table 160‚ “LoPAPR VPD Fields‚”
on page 343) of the first or ‘marked’ processor enclosure.
And worse, it mixes "vm,uuid" which is QEMU specific concept to uniquely
identify guests, with "system-id" which is about the host :-\
All of this is very confusing and need to be sorted out before building
anything on top of it. Especially since "model" and "system-id" are
supposed to derive from VPD IIUC.
I guess that we should first decide what we really want to expose
in "system-id" and "model": what we have now ? the same as in
"host-serial" and "host-model", ie. user configurable ? Must we
stay compatible with existing setups ? In any case, I'm afraid that
we have to diverge from PAPR somehow, since it obviously doesn't
care about the security concerns that motivated recent changes
for "host-serial" and "host-model"...
Many important changes should be done to solve these inconsistencies.
So, I saw in the 'get-vpd' RTAS a manner to return host information
and that works with live-migration.
Yes it does indeed allow that, among other things. My concern is more that
PAPR clearly indicates that the "system-id" and "model" in the root node
are derived from the VPD, and this series is about to tie the VPD TM and
VPD SE keywords to something else that isn't documented in PAPR...
The more I look at the "host-serial" and "host-model" properties, the more
I have the impression that they serve the same purpose as "system-id" and
"model" in PAPR (at least when peeking into the device tree of a PowerVM
LPAR as shown somewhere ^^)... what about unifying these ? It would likely
impact some guest software that use this to guess the platform type, like
powerpc-utils for example:
} else if (strstr(line, "IBM pSeries (emulated by qemu)")) {
rc = PLATFORM_POWERKVM_GUEST;
break;
} else if (strstr(line, "pSeries")) {
but this is fragile and should be improved anyway...
Since it's a POWER specific
functionality, may 'ibm,get-vpd' export host information if the
guest instance allows it? Or is it better return only the 'host-serial'
and 'host-model' content, like in the patch "spapr: Simplify handling
of host-serial and host-model values"?
I've spent some time reading PAPR on this topic and I'm not sure that
"ibm,get-vpd" is the way to go for what you were trying to achieve
initially (ie, obtain up-to-date host model and serial after migration).
Have you looked at RTAS "ibm,update-properties" ?
7.4.8 ibm,update-properties RTAS Call
This RTAS call is used to report updates to the properties changed
due to a massive platform reconfiguration such as when the partition
is migrated between machines.
This explicitly covers updates to "system-id" and "model". Maybe it is
time to do as Ben was suggesting a long time ago when "host-serial"
and "host-model" were introduced [1]:
On Tue, 2014-07-08 at 12:49 +0200, Alexander Graf wrote:
> Please be aware that all of the above is bogus when you start
> thinking
> about live migration.
What's probably where we need to start thinking about implementing
migration according to PAPR :-)
IE. With pre and post-migration notifications to the guest including
device-tree updates.
Cheers,
Ben.
[1] https://patchwork.ozlabs.org/patch/367792/#813547
Cheers,
The 'ibm,update-properties' and 'ibm,update-nodes' RTAS report which DT
nodes was modified. So, to implement this approach, the QEMU should change
the DT nodes when the live-migration finish and some service in the guest
need to call these RTAS to discovery what nodes was changed. Is it the
right way?
If QEMU on the target is started with different "host-serial" and
"host-model", the DT in QEMU already has the new value. No need to
change anything. Appart from that, yes, QEMU should generate a PRRN
event at post load to notify the guest, which in turns do the RTAS
calls to get the updates.
Assuming that in new pseries machine won't be possible choose
'passthrough' options to 'host-serial' and 'host-model' (last patch of
dgibson about this), it's necessary get the host information and set it
as string in these options. So, if we use the same qemu options in a
live-migration scenario for src and dst (libvirt do that), these
properties will remain the same. Is this behavior expected?
The recent fixes around "host-serial" and "host-model" simply moved
the decision to expose host data to the upper layer, ie. libvirt
which should be involved in this discussion.
Cc'ing Andrea for expertise. Problem exposed below.
The pseries machine used to expose the content of the host's
/proc/device-tree/system-id and /proc/device-tree/model in the guest
DT. This led to a CVE and QEMU doesn't do that anymore for new machine
types. Instead, two new properties where added to the pseries machine:
pseries-4.0.host-serial=string (Host serial number to advertise in guest device
tree)
pseries-4.0.host-model=string (Host model to advertise in guest device tree)
It is up to the caller to pass something... which may be anything,
including something like $(cat /proc/device-tree/system-id) or
randomly generated.
Is there a chance libvirt can be taught to pass a different string
to the target QEMU in case of migration ?