linux-kernel - Re: [PATCH 00/14] paravirt: cleanup and reorg

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Message-ID: <20250911074817.GX3245006@noisy.programming.kicks-ass.net>
Date: Thu, 11 Sep 2025 09:48:17 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Juergen Gross <jgross@...e.com>
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Subject: Re: [PATCH 00/14] paravirt: cleanup and reorg

On Thu, Sep 11, 2025 at 08:34:19AM +0200, Juergen Gross wrote:
> Some cleanups and reorg of paravirt code and headers:
> 
> - The first 2 patches should be not controversial at all, as they
>   remove just some no longer needed #include and struct forward
>   declarations.
> 
> - The 3rd patch is removing CONFIG_PARAVIRT_DEBUG, which IMO has
>   no real value, as it just changes a crash to a BUG() (the stack
>   trace will basically be the same). As the maintainer of the main
>   paravirt user (Xen) I have never seen this crash/BUG() to happen.
> 
> - The 4th patch is just a movement of code.
> 
> - I don't know for what reason asm/paravirt_api_clock.h was added,
>   as all archs supporting it do it exactly in the same way. Patch
>   5 is removing it.
> 
> - Patches 6-12 are streamlining the paravirt clock interfaces by
>   using a common implementation across architectures where possible
>   and by moving the related code into common sched code, as this is
>   where it should live.
> 
> - Patches 13+14 are more like RFC material: patch 13 is doing some
>   preparation work to enable patch 14 to move all spinlock related
>   paravirt functions into qspinlock.h. If this approach is accepted,
>   I'd like to continue with this work by moving most (or all?)
>   paravirt functions from paravirt.h into the headers where their
>   native counterparts are defined. This is meant to keep the native
>   and paravirt function definitions together in one place and
>   hopefully to be able to reduce the include hell with paravirt.
> 
> Juergen Gross (14):
>   x86/paravirt: remove not needed includes of paravirt.h
>   x86/paravirt: remove some unneeded struct declarations
>   x86/paravirt: remove PARAVIRT_DEBUG config option
>   x86/paravirt: move thunk macros to paravirt_types.h
>   paravirt: remove asm/paravirt_api_clock.h
>   sched: move clock related paravirt code to kernel/sched
>   arm/paravirt: use common code for paravirt_steal_clock()
>   arm64/paravirt: use common code for paravirt_steal_clock()
>   loongarch/paravirt: use common code for paravirt_steal_clock()
>   riscv/paravirt: use common code for paravirt_steal_clock()
>   x86/paravirt: use common code for paravirt_steal_clock()
>   x86/paravirt: move paravirt_sched_clock() related code into tsc.c
>   x86/paravirt: allow pv-calls outside paravirt.h
>   x86/pvlocks: move paravirt spinlock functions into qspinlock.h

With the note that tip typically likes a capital after the prefix, like:

  x86/paravirt: Remove unneeded includes of paravirt.h

For 1-12:

  Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>


Now, as to the last two, I'm not sure. Leaking those macros out of PV
isn't particularly nice, then again, not the end of the world either.
Just not sure.