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From:   "Czerwacki, Eial" <eial.czerwacki@sap.com>
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>
CC:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "Arsh, Leonid" <leonid.arsh@sap.com>,
        "Twaig, Oren" <oren.twaig@sap.com>,
        SAP vSMP Linux Maintainer <linux.vsmp@sap.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Dan Carpenter <dan.carpenter@oracle.com>,
        Andra Paraschiv <andraprs@amazon.com>,
        Borislav Petkov <bp@suse.de>,
        Brijesh Singh <brijesh.singh@amd.com>,
        Eric Biggers <ebiggers@google.com>, Fei Li <fei1.li@intel.com>,
        Hans de Goede <hdegoede@redhat.com>,
        Jens Axboe <axboe@kernel.dk>,
        Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Subject: Re: [PATCH v2] drivers/virt/vSMP: new driver
Thread-Topic: [PATCH v2] drivers/virt/vSMP: new driver
Thread-Index: AQHYuErwCwPojP5fak60UhGlJnJEo62/OPAAgAACsWWAAB5kAIAADNqvgAACQwCAAAE9j4AAFa6AgAAESN6AAATmgIAAA1dF
Date:   Thu, 25 Aug 2022 12:38:46 +0000
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>On Thu, Aug 25, 2022 at 12:02:12PM +0000, Czerwacki, Eial wrote:=0A=
>> >On Thu, Aug 25, 2022 at 10:41:28AM +0000, Czerwacki, Eial wrote:=0A=
>> >> >On Thu, Aug 25, 2022 at 10:16:59AM +0000, Czerwacki, Eial wrote:=0A=
>> >> >> >> >And why is your version file a binary file?=A0 It should just =
be a small=0A=
>> >> >> >> >text string, right?=0A=
>> >> >> >> not so small, it can reach up to 512kb.=0A=
>> >> >> >=0A=
>> >> >> >That was not obvious at all.=A0 Please document this.=0A=
>> >> >> where should the document be?=0A=
>> >> >> in the code as a comment or in another file?=0A=
>> >> >=0A=
>> >> >In the Documentation/ABI/ file that describes this file.=0A=
>> >> ok, will place it there=0A=
>> >> =0A=
>> >> >=0A=
>> >> >> >And how in the world is a "version" that big?=A0 What exactly doe=
s this=0A=
>> >> >> >contain?=0A=
>> >> >> it 's size depends on the number of resources it uses.=0A=
>> >> >> here is an example:=0A=
>> >> >> :~> cat /sys/hypervisor/vsmp/version=A0 =0A=
>> >> >> SAP vSMP Foundation: 10.6.2862.0 (Aug 22 2022 15:21:02)=0A=
>> >> >> System configuration:=0A=
>> >> >>=A0=A0=A0 Boards:=A0=A0=A0=A0=A0 2=0A=
>> >> >>=A0=A0=A0=A0=A0=A0 1 x Proc. + I/O + Memory=0A=
>> >> >>=A0=A0=A0=A0=A0=A0 1 x NVM devices (Amazon.com Amazon EC2 NVMe Inst=
ance Storage)=0A=
>> >> >>=A0=A0=A0 Processors:=A0 1, Cores: 2, Threads: 4=0A=
>> >> >>=A0=A0=A0=A0=A0=A0=A0 Intel(R) Xeon(R) Platinum 8124M CPU @ 3.00GHz=
 Stepping 04=0A=
>> >> >>=A0=A0=A0 Memory (MB): 30976 (of 103192), Cache: 7527, Private: 646=
89=0A=
>> >> >>=A0=A0=A0=A0=A0=A0 1 x=A0 6400MB=A0=A0=A0 [ 7825/ 321/ 1104]=A0=A0=
=A0=A0=A0 =0A=
>> >> >>=A0=A0=A0=A0=A0=A0 1 x 24576MB=A0=A0=A0 [95367/7206/63585]=A0=A0=A0=
=A0=A0=A0 00:1f.0#1=0A=
>> >> >>=A0=A0=A0 Boot device: [HDD] NVMe: Amazon Elastic Block Store=A0=A0=
=A0=A0=A0=A0=A0 =0A=
>> >> >> Supported until: Aug 22 2024=0A=
>> >> >=0A=
>> >> >That is crazy, and is not a version.=A0 It's a "configuration".=0A=
>> >> it is called version for history reasons...=0A=
>> >=0A=
>> >There is no "history" here, you can create whatever sane interface you=
=0A=
>> >want right now, there is no backwards compatible issues involved at all=
.=0A=
>> you are correct, however, it depends on how much change the hypervisor c=
ode requires=0A=
>> if any (latter is preferable)=0A=
>=0A=
>I do not understand, again, what tool consumes this today?=0A=
there are monitoring utils that parses it.=0A=
see comment below for more on this=0A=
=0A=
>=0A=
>> >> >See above, make it text only for the version.=A0 If you want to expo=
rt=0A=
>> >> >other things, be explicit and make them "one value per sysfs file" o=
r=0A=
>> >> >use debugfs for debugging things that no one relies on.=0A=
>> >> so you suggest braking the summery into files, e.g. one for cpus, one=
 for ram and etcetera?=0A=
>> >=0A=
>> >Again, who uses this information and what is it used for?=0A=
>> >=0A=
>> >thanks,=0A=
>> >=0A=
>> >greg k-h=0A=
>> =0A=
>> both user who uses the product and the development team.=0A=
>> it is used to provide a summery of the system. for example, which device=
s are used=0A=
>> by the hypervisor.=0A=
>=0A=
>That's a very odd way to display this as a free-flowing, impossible to=0A=
>parse, file.=A0 Please use something that will be able to be maintained=0A=
>over time.=0A=
>=0A=
>thanks,=0A=
>=0A=
>greg k-h=0A=
=0A=
your suggestion to brake the configuration seems sound, we will implement t=
hat and=0A=
provide a new patch=0A=
=0A=
Thanks for the reviews.=0A=
=0A=
Eial=