linux-kernel - Re: [PATCH v3 03/13] powerpc/mm: implement arch_flush_lazy_mmu

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Message-ID: <60c55686-87dd-46d0-884e-80f7d423663b@redhat.com>
Date: Thu, 23 Oct 2025 21:36:48 +0200
From: David Hildenbrand <david@...hat.com>
To: Kevin Brodsky <kevin.brodsky@....com>, linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org, Alexander Gordeev <agordeev@...ux.ibm.com>,
 Andreas Larsson <andreas@...sler.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Boris Ostrovsky <boris.ostrovsky@...cle.com>, Borislav Petkov
 <bp@...en8.de>, Catalin Marinas <catalin.marinas@....com>,
 Christophe Leroy <christophe.leroy@...roup.eu>,
 Dave Hansen <dave.hansen@...ux.intel.com>,
 "David S. Miller" <davem@...emloft.net>, "H. Peter Anvin" <hpa@...or.com>,
 Ingo Molnar <mingo@...hat.com>, Jann Horn <jannh@...gle.com>,
 Juergen Gross <jgross@...e.com>, "Liam R. Howlett"
 <Liam.Howlett@...cle.com>, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Madhavan Srinivasan <maddy@...ux.ibm.com>,
 Michael Ellerman <mpe@...erman.id.au>, Michal Hocko <mhocko@...e.com>,
 Mike Rapoport <rppt@...nel.org>, Nicholas Piggin <npiggin@...il.com>,
 Peter Zijlstra <peterz@...radead.org>, Ryan Roberts <ryan.roberts@....com>,
 Suren Baghdasaryan <surenb@...gle.com>, Thomas Gleixner
 <tglx@...utronix.de>, Vlastimil Babka <vbabka@...e.cz>,
 Will Deacon <will@...nel.org>, Yeoreum Yun <yeoreum.yun@....com>,
 linux-arm-kernel@...ts.infradead.org, linuxppc-dev@...ts.ozlabs.org,
 sparclinux@...r.kernel.org, xen-devel@...ts.xenproject.org, x86@...nel.org
Subject: Re: [PATCH v3 03/13] powerpc/mm: implement arch_flush_lazy_mmu_mode()

On 15.10.25 10:27, Kevin Brodsky wrote:
> Upcoming changes to the lazy_mmu API will cause
> arch_flush_lazy_mmu_mode() to be called when leaving a nested
> lazy_mmu section.
> 
> Move the relevant logic from arch_leave_lazy_mmu_mode() to
> arch_flush_lazy_mmu_mode() and have the former call the latter.
> 
> Signed-off-by: Kevin Brodsky <kevin.brodsky@....com>
> ---
>   .../powerpc/include/asm/book3s/64/tlbflush-hash.h | 15 +++++++++++----
>   1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/book3s/64/tlbflush-hash.h b/arch/powerpc/include/asm/book3s/64/tlbflush-hash.h
> index 146287d9580f..7704dbe8e88d 100644
> --- a/arch/powerpc/include/asm/book3s/64/tlbflush-hash.h
> +++ b/arch/powerpc/include/asm/book3s/64/tlbflush-hash.h
> @@ -41,6 +41,16 @@ static inline void arch_enter_lazy_mmu_mode(void)
>   	batch->active = 1;
>   }
>   
> +static inline void arch_flush_lazy_mmu_mode(void)
> +{
> +	struct ppc64_tlb_batch *batch;
> +
> +	batch = this_cpu_ptr(&ppc64_tlb_batch);

The downside is the double this_cpu_ptr() now on the 
arch_leave_lazy_mmu_mode() path.

You could just have a helper function that is called by either or just 
... leave arch_leave_lazy_mmu_mode() alone and just replicate the two 
statements here in arch_flush_lazy_mmu_mode().

I would do just that :)

-- 
Cheers

David / dhildenb