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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <46d9bb24-1603-4c75-8723-84a821b3c46c-agordeev@linux.ibm.com>
Date: Thu, 30 Oct 2025 17:34:00 +0100
From: Alexander Gordeev <agordeev@...ux.ibm.com>
To: Kevin Brodsky <kevin.brodsky@....com>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        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 Hildenbrand <david@...hat.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

On Thu, Oct 30, 2025 at 11:28:53AM +0100, Kevin Brodsky wrote:
> On 29/10/2025 17:41, Alexander Gordeev wrote:
> > On Wed, Oct 29, 2025 at 10:09:04AM +0000, Kevin Brodsky wrote:
> >
> > Hi Kevin,
> >
> >> +#ifdef CONFIG_ARCH_HAS_LAZY_MMU_MODE
> >> +static inline bool in_lazy_mmu_mode(void)
> >> +{
> >> +	return current->lazy_mmu_state.active;
> > Whether (nesting_level > 0) is more correct check?
> > Otherwise, it returns false while in paused mode.
> 
> That's exactly the intention. Lazy MMU is disabled while paused. The
> users of that helper want to know if lazy MMU is currently enabled (to
> decide whether to batch updates for instance); whether this is because
> we are paused or not in any lazy_mmu section (nesting_level == 0) makes
> no difference.
> 
> > May be check both nesting_level and active and also introduce
> > in_lazy_mmu_paused_mode() right away to avoid any confusion?
> 
> Can you think of any situation where a caller would specifically want to
> know that lazy MMU is paused?

I thought I do, but in_lazy_mmu_mode() alone works just fine,
as you described (at least for now).

> - Kevin

Thanks!