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[80.187.83.189]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-426ce5833dcsm468974f8f.19.2025.10.09.12.28.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 09 Oct 2025 12:29:00 -0700 (PDT) Message-ID: <4858074d-f058-41ec-a581-a8254b8cc2d7@redhat.com> Date: Thu, 9 Oct 2025 21:28:58 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 6/8] mm: Introduce deferred freeing for kernel page tables To: Lu Baolu , Joerg Roedel , Will Deacon , Robin Murphy , Kevin Tian , Jason Gunthorpe , Jann Horn , Vasant Hegde , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , Alistair Popple , Peter Zijlstra , Uladzislau Rezki , Jean-Philippe Brucker , Andy Lutomirski , Yi Lai Cc: iommu@lists.linux.dev, security@kernel.org, x86@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Dave Hansen References: <20250919054007.472493-1-baolu.lu@linux.intel.com> <20250919054007.472493-7-baolu.lu@linux.intel.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: 16fytky8kqtg9t366ead6m5k6a5hnjef X-Rspamd-Queue-Id: 9CC1818000E X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1760038144-479091 X-HE-Meta: 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 FVKNHy07 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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: On 19.09.25 07:40, Lu Baolu wrote: > From: Dave Hansen > > This introduces a conditional asynchronous mechanism, enabled by > CONFIG_ASYNC_PGTABLE_FREE. When enabled, this mechanism defers the freeing > of pages that are used as page tables for kernel address mappings. These > pages are now queued to a work struct instead of being freed immediately. > > This deferred freeing provides a safe context for a future patch to add > an IOMMU-specific callback, which might be expensive on large-scale > systems. This ensures the necessary IOMMU cache invalidation is performed > before the page is finally returned to the page allocator outside of any > critical, non-sleepable path. > > Signed-off-by: Dave Hansen > Signed-off-by: Lu Baolu > Reviewed-by: Jason Gunthorpe > Reviewed-by: Kevin Tian > --- Can we please squash #7 in here and make sure to call the config knob something that indicates that it is for *kernel* page tables only? ASYNC_KERNEL_PGTABLE_FREE or sth like that. -- Cheers David / dhildenb