linux-kernel - Re: [PATCH] mm/mmu_gather: send tlb_remove_table_smp

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: <a6ee41b39f3f516aab0f7fb327620cb2a43eeaca.camel@redhat.com>
Date:   Wed, 22 Mar 2023 16:11:44 +0200
From:   ypodemsk@...hat.com
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     will@...nel.org, aneesh.kumar@...ux.ibm.com,
        akpm@...ux-foundation.org, npiggin@...il.com, arnd@...db.de,
        linux-arch@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, mtosatti@...hat.com,
        ppandit@...hat.com, alougovs@...hat.com,
        David Hildenbrand <david@...hat.com>
Subject: Re: [PATCH] mm/mmu_gather: send tlb_remove_table_smp_sync IPI only
 to MM CPUs

On Mon, 2023-03-20 at 09:49 +0100, Peter Zijlstra wrote:
> On Sun, Mar 12, 2023 at 10:09:45AM +0200, Yair Podemsky wrote:
> > Currently the tlb_remove_table_smp_sync IPI is sent to all CPUs
> > indiscriminately, this causes unnecessary work and delays notable
> > in
> > real-time use-cases and isolated cpus, this patch will limit this
> > IPI to
> > only be sent to cpus referencing the effected mm and are currently
> > in
> > kernel space.
> 
> Did you validate that all architectures for which this is relevant
> actually set bits in mm_cpumask() ?
> 
Hi Peter,
Thank you for bringing this to my attention.
I reviewed the architectures using the MMU_GATHER_RCU_TABLE_FREE:
arm, powerpc, s390, sparc and x86 set the bit when switching process
in.
for arm64 removed set/clear bit in 38d96287504a ("arm64: mm: kill
mm_cpumask usage")
The reason given was that mm_cpumask was not used.
Given that we now have a use for it, I will add a patch to revert.
Thanks
Yair