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Fri, 07 Nov 2025 18:33:38 -0800 (PST) Received: from dw-tp ([171.76.85.117]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-ba8f8d7eedcsm6587378a12.2.2025.11.07.18.33.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 07 Nov 2025 18:33:37 -0800 (PST) From: Ritesh Harjani (IBM) To: Kevin Brodsky , linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Alexander Gordeev , Andreas Larsson , Andrew Morton , Boris Ostrovsky , Borislav Petkov , Catalin Marinas , Christophe Leroy , Dave Hansen , David Hildenbrand , "David S. Miller" , David Woodhouse , "H. Peter Anvin" , Ingo Molnar , Jann Horn , Juergen Gross , "Liam R. Howlett" , Lorenzo Stoakes , Madhavan Srinivasan , Michael Ellerman , Michal Hocko , Mike Rapoport , Nicholas Piggin , Peter Zijlstra , Ryan Roberts , Suren Baghdasaryan , Thomas Gleixner , Vlastimil Babka , Will Deacon , Yeoreum Yun , linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, sparclinux@vger.kernel.org, xen-devel@lists.xenproject.org, x86@kernel.org, Venkat Rao Bagalkote Subject: Re: [PATCH v4 01/12] powerpc/64s: Do not re-activate batched TLB flush In-Reply-To: Date: Sat, 08 Nov 2025 06:05:17 +0530 Message-ID: <87cy5t4b0a.ritesh.list@gmail.com> References: <20251029100909.3381140-1-kevin.brodsky@arm.com> <20251029100909.3381140-2-kevin.brodsky@arm.com> <87qzud42n1.ritesh.list@gmail.com> MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 974571A0007 X-Stat-Signature: 3qr8646u3mwyx58k4s597nihym418u3t X-Rspam-User: X-HE-Tag: 1762569219-840995 X-HE-Meta: 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 aGAZlimM 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Kevin Brodsky writes: > On 05/11/2025 02:46, Ritesh Harjani (IBM) wrote: >> Kevin Brodsky writes: >> >>> From: Alexander Gordeev >>> >>> Since commit b9ef323ea168 ("powerpc/64s: Disable preemption in hash >>> lazy mmu mode") a task can not be preempted while in lazy MMU mode. >>> Therefore, the batch re-activation code is never called, so remove it. >>> >>> Signed-off-by: Alexander Gordeev >>> Signed-off-by: Kevin Brodsky >>> --- >>> arch/powerpc/include/asm/thread_info.h | 2 -- >>> arch/powerpc/kernel/process.c | 25 ------------------------- >>> 2 files changed, 27 deletions(-) >>> >> Since the commit referenced in above disables the preemption in >> arch_enter_lazy_mmu(), so the expectation is that we will never be >> context switched while in lazy_mmu, hence the code changes in >> switch_to() around __flush_tlb_pending() should ideally never be called. > > Correct, that's the idea. > >> With this analysis - the patch looks good to me. I will give this entire >> patch series a try on Power HW with Hash mmu too (which uses lazy mmu and >> let you know the results of that)! > > That'd be very appreciated, thanks a lot! > I did give this patch series a run on Power10 with Hash MMU. I ran the following stress-ng tests and didn't observe any issues (kernel warnings) so far. stress-ng --all 0 -t 60s --perf -v --verify \ --tlb-shootdown 0 \ --fault 0 \ --userfaultfd 0 \ --fork 0 \ --exec 0 \ --memfd 0 \ --numa 0 \ --pkey 0 \ --remap 0 \ --vm 0 \ --rmap 0 \ -x swap,pagemove (Note not all options shown here will work with --verify) Let me know what else I can run for validation? Do you know of any specific tests for validation of lazy mmu feature? >> For this patch please feel free to add: >> Reviewed-by: Ritesh Harjani (IBM) >> >> >> CC: Venkat who also runs CI on linux Power HW for upstream testing :) > > Ack, will Cc you both in the next version. Sure. Thanks! -ritesh