linux-kernel - Re: [PATCH v2] drivers/virt/vSMP: new driver

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Date:   Thu, 25 Aug 2022 12:02:12 +0000
From:   "Czerwacki, Eial" <eial.czerwacki@....com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Arsh, Leonid" <leonid.arsh@....com>,
        "Twaig, Oren" <oren.twaig@....com>,
        SAP vSMP Linux Maintainer <linux.vsmp@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Andra Paraschiv <andraprs@...zon.com>,
        Borislav Petkov <bp@...e.de>,
        Brijesh Singh <brijesh.singh@....com>,
        Eric Biggers <ebiggers@...gle.com>, Fei Li <fei1.li@...el.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Jens Axboe <axboe@...nel.dk>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
Subject: Re: [PATCH v2] drivers/virt/vSMP: new driver

>On Thu, Aug 25, 2022 at 10:41:28AM +0000, Czerwacki, Eial wrote:
>> >On Thu, Aug 25, 2022 at 10:16:59AM +0000, Czerwacki, Eial wrote:
>> >> >> >And why is your version file a binary file?  It should just be a small
>> >> >> >text string, right?
>> >> >> not so small, it can reach up to 512kb.
>> >> >
>> >> >That was not obvious at all.  Please document this.
>> >> where should the document be?
>> >> in the code as a comment or in another file?
>> >
>> >In the Documentation/ABI/ file that describes this file.
>> ok, will place it there
>> 
>> >
>> >> >And how in the world is a "version" that big?  What exactly does this
>> >> >contain?
>> >> it 's size depends on the number of resources it uses.
>> >> here is an example:
>> >> :~> cat /sys/hypervisor/vsmp/version  
>> >> SAP vSMP Foundation: 10.6.2862.0 (Aug 22 2022 15:21:02)
>> >> System configuration:
>> >>    Boards:      2
>> >>       1 x Proc. + I/O + Memory
>> >>       1 x NVM devices (Amazon.com Amazon EC2 NVMe Instance Storage)
>> >>    Processors:  1, Cores: 2, Threads: 4
>> >>        Intel(R) Xeon(R) Platinum 8124M CPU @ 3.00GHz Stepping 04
>> >>    Memory (MB): 30976 (of 103192), Cache: 7527, Private: 64689
>> >>       1 x  6400MB    [ 7825/ 321/ 1104]      
>> >>       1 x 24576MB    [95367/7206/63585]       00:1f.0#1
>> >>    Boot device: [HDD] NVMe: Amazon Elastic Block Store        
>> >> Supported until: Aug 22 2024
>> >
>> >That is crazy, and is not a version.  It's a "configuration".
>> it is called version for history reasons...
>
>There is no "history" here, you can create whatever sane interface you
>want right now, there is no backwards compatible issues involved at all.
you are correct, however, it depends on how much change the hypervisor code requires
if any (latter is preferable)

>
>> >See above, make it text only for the version.  If you want to export
>> >other things, be explicit and make them "one value per sysfs file" or
>> >use debugfs for debugging things that no one relies on.
>> so you suggest braking the summery into files, e.g. one for cpus, one for ram and etcetera?
>
>Again, who uses this information and what is it used for?
>
>thanks,
>
>greg k-h

both user who uses the product and the development team.
it is used to provide a summery of the system. for example, which devices are used
by the hypervisor.

Thanks,

Eial