linux-kernel - Re: [PATCH v4 07/12] mm: enable lazy

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Message-ID: <ae1236da-2647-4d53-bf4d-ff8fc32eb734@redhat.com>
Date: Sat, 1 Nov 2025 13:22:42 +0100
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>,
 David Woodhouse <dwmw2@...radead.org>, "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 v4 07/12] mm: enable lazy_mmu sections to nest

>   static inline void lazy_mmu_mode_pause(void)
>   {
> +	struct lazy_mmu_state *state = &current->lazy_mmu_state;
> +
> +	VM_WARN_ON(state->nesting_level == 0 || !state->active);
> +
> +	state->active = false;
>   	arch_leave_lazy_mmu_mode();

Just one question:

Don't we want to allow for pause/resume when not enabled? Would seem 
valid to me, because pause/resume code should actually not worry about 
that, right?

if (!state->nesting_level) {
	VM_WARN_ON(state->active);
	return;
}
VM_WARN_ON(!state->active);
state->active = false;
arch_leave_lazy_mmu_mode();

-- 
Cheers

David / dhildenb