linux-kernel - Re: [PATCH v2 2/3] hyperv: Change hv_root

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Message-ID: <3b667a16-3ea9-474b-81c1-a5dc7122c71e@linux.microsoft.com>
Date: Fri, 21 Feb 2025 10:38:58 -0800
From: Easwar Hariharan <eahariha@...ux.microsoft.com>
To: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
Cc: MUKESH RATHOR <mukeshrathor@...rosoft.com>, eahariha@...ux.microsoft.com,
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Subject: Re: [PATCH v2 2/3] hyperv: Change hv_root_partition into a function

On 2/21/2025 10:10 AM, Nuno Das Neves wrote:
> On 2/20/2025 2:59 PM, MUKESH RATHOR wrote:
>>
>>
>> On 2/20/25 14:56, Easwar Hariharan wrote:
>>  > On 2/20/2025 1:59 PM, MUKESH RATHOR wrote:
>>  >>
>>  >>
>>  >> On 2/20/25 10:33, Nuno Das Neves wrote:
>>  >>   > Introduce hv_current_partition_type to store the partition type
>>  >>   > as an enum.
>>  >>   >
>>  >>   > Right now this is limited to guest or root partition, but there will
>>  >>   > be other kinds in future and the enum is easily extensible.
>>  >>   >
>>  >>   > Set up hv_current_partition_type early in Hyper-V initialization
>> with
>>  >>   > hv_identify_partition_type(). hv_root_partition() just queries this
>>  >>   > value, and shouldn't be called before that.
>>  >>   >
>>  >>   > Making this check into a function sets the stage for adding a config
>>  >>   > option to gate the compilation of root partition code. In
>> particular,
>>  >>   > hv_root_partition() can be stubbed out always be false if root
>>  >>   > partition support isn't desired.
>>  >>   >
>>  >>   > Signed-off-by: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
>>  >>   > ---
>>  >>   >   arch/arm64/hyperv/mshyperv.c       |  2 ++
>>  >>   >   arch/x86/hyperv/hv_init.c          | 10 ++++-----
>>  >>   >   arch/x86/kernel/cpu/mshyperv.c     | 24 ++------------------
>>  >>   >   drivers/clocksource/hyperv_timer.c |  4 ++--
>>  >>   >   drivers/hv/hv.c                    | 10 ++++-----
>>  >>   >   drivers/hv/hv_common.c             | 35
>> +++++++++++++++++++++++++-----
>>  >>   >   drivers/hv/vmbus_drv.c             |  2 +-
>>  >>   >   drivers/iommu/hyperv-iommu.c       |  4 ++--
>>  >>   >   include/asm-generic/mshyperv.h     | 15 +++++++++++--
>>  >>   >   9 files changed, 61 insertions(+), 45 deletions(-)
>>  >>   >
>>  >
>>  > <snip>
>>  >
>>  >>   > @@ -34,8 +34,11 @@
>>  >>   >   u64 hv_current_partition_id = HV_PARTITION_ID_SELF;
>>  >>   >   EXPORT_SYMBOL_GPL(hv_current_partition_id);
>>  >>   >
>>  >>   > +enum hv_partition_type hv_current_partition_type;
>>  >>   > +EXPORT_SYMBOL_GPL(hv_current_partition_type);
>>  >>   > +
>>  >>
>>  >> nit: if possible and not too late, can we please use more Unix
>>  >> style naming, eg, hv_curr_ptid and hv_curr_pt_type rather than this
>>  >> long windows style names that causes unnecessary line wraps/splits.
>>  >>
>>  >> Thanks,
>>  >> -Mukesh
>>  >>
>>  >
>>  > Per
>> https://docs.kernel.org/process/coding-style.html#naming
>>  >
>>  > GLOBAL variables (to be used only if you really need them) need to
>> have descriptive names,
>>  > as do global functions. If you have a function that counts the number
>> of active users,
>>  > you should call that count_active_users() or similar, you should not
>> call it cntusr().
>>
>> Thant's hardly a fair comparison. Suggestion was NOT hvptid.
>>
> I'm in favor of shortening the names when the abbreviation is common and
> therefore still perfectly clear to anyone reading it - e.g. "curr" is
> a perfectly acceptable abbreviation of "current", in my view.
> 
> I think abbreviating "partition" to "pt" is probably not a good fit for
> global variables. Anyone seeing a variable with the word "partition"
> (and hv_ prefix) can go look up what a Hyper-V partition is if they don't
> know, but "pt" would be completely impenetrable without reading through a
> fair amount of the code that uses it to figure out what it refers to.
> 
> I think even slightly longer abbreviations like "part", "ptn", "prt", or
> "prtn" are not good enough unfortunately... the word "partition" just
> doesn't lend itself to abbreviation in an obvious way.
> 
> So, for this patch I'm fine with changing it to "hv_curr_partition_type"
> which saves a few characters.
> 

FWIW, I generally prioritize readability of code and your proposal neatly
splits the difference. Also, it's your patch, so you get to make the decision. :)

Thanks,
Easwar (he/him)