From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from shelob.surriel.com (shelob.surriel.com [96.67.55.147]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E9C941EC00C for ; Mon, 20 Jan 2025 17:11:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=96.67.55.147 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737393119; cv=none; b=YnN2zuIPSKuQP0pY9n5PdkowSmek5Nw9VS55aRMwZtRv+nGodSq6Uwlkm8AmAAdYK6b+QR0bAmhypU+Qo9S3DOrU6ogVKGwgZaEhb0wEN1AQWy+unmPTmRU+SOZenrbTUw6OE2+kFhV3hDRMD7YMv9rHi7krMp5kaFR6Ryna/cs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737393119; c=relaxed/simple; bh=T6DR1GhtRx01DmGCJEBUd44HDUH0Qg64Bv9y3dAMppo=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=TIk6K9jkdJIXKtd31xkdurBQKCsK4kRoo+yIo5AvFpPtApbMUu13+HOQe10bx1Fe4quo82r+JjSOkEsz3ZJL/vSwiEyrW/7Vus/3es45Fk2LSZxYyKjTu713oaN6OA3ickol4Ir+SJTbC5RfJpKK4Aai1lJupRTecd8nakZCLRw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=surriel.com; spf=pass smtp.mailfrom=shelob.surriel.com; arc=none smtp.client-ip=96.67.55.147 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=surriel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=shelob.surriel.com Received: from fangorn.home.surriel.com ([10.0.13.7]) by shelob.surriel.com with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.97.1) (envelope-from ) id 1tZvJJ-000000001cE-0Bkc; Mon, 20 Jan 2025 12:11:37 -0500 Message-ID: Subject: Re: [PATCH v5 10/12] x86,tlb: do targeted broadcast flushing from tlbbatch code From: Rik van Riel To: Nadav Amit , x86@kernel.org Cc: linux-kernel@vger.kernel.org, bp@alien8.de, peterz@infradead.org, dave.hansen@linux.intel.com, zhengqi.arch@bytedance.com, thomas.lendacky@amd.com, kernel-team@meta.com, linux-mm@kvack.org, akpm@linux-foundation.org, jannh@google.com, mhklinux@outlook.com, andrew.cooper3@citrix.com Date: Mon, 20 Jan 2025 12:11:37 -0500 In-Reply-To: <11d9f41a-eae3-43a1-90bc-eb5c69020002@gmail.com> References: <20250116023127.1531583-1-riel@surriel.com> <20250116023127.1531583-11-riel@surriel.com> <13bc0c49-09a4-434e-bd35-1ea50be38e25@gmail.com> <4dcf2b4ecaede883e2c7f6af3db58a4f6afaf4ad.camel@surriel.com> <2975f6a4-58ef-4499-b177-4b73ead4c670@gmail.com> <2c93b3f17e658483e3ea03ca3f0a717668fd117d.camel@surriel.com> <11d9f41a-eae3-43a1-90bc-eb5c69020002@gmail.com> Autocrypt: addr=riel@surriel.com; prefer-encrypt=mutual; keydata=mQENBFIt3aUBCADCK0LicyCYyMa0E1lodCDUBf6G+6C5UXKG1jEYwQu49cc/gUBTTk33A eo2hjn4JinVaPF3zfZprnKMEGGv4dHvEOCPWiNhlz5RtqH3SKJllq2dpeMS9RqbMvDA36rlJIIo47 Z/nl6IA8MDhSqyqdnTY8z7LnQHqq16jAqwo7Ll9qALXz4yG1ZdSCmo80VPetBZZPw7WMjo+1hByv/ lvdFnLfiQ52tayuuC1r9x2qZ/SYWd2M4p/f5CLmvG9UcnkbYFsKWz8bwOBWKg1PQcaYHLx06sHGdY dIDaeVvkIfMFwAprSo5EFU+aes2VB2ZjugOTbkkW2aPSWTRsBhPHhV6dABEBAAG0HlJpayB2YW4gU mllbCA8cmllbEByZWRoYXQuY29tPokBHwQwAQIACQUCW5LcVgIdIAAKCRDOed6ShMTeg05SB/986o gEgdq4byrtaBQKFg5LWfd8e+h+QzLOg/T8mSS3dJzFXe5JBOfvYg7Bj47xXi9I5sM+I9Lu9+1XVb/ r2rGJrU1DwA09TnmyFtK76bgMF0sBEh1ECILYNQTEIemzNFwOWLZZlEhZFRJsZyX+mtEp/WQIygHV WjwuP69VJw+fPQvLOGn4j8W9QXuvhha7u1QJ7mYx4dLGHrZlHdwDsqpvWsW+3rsIqs1BBe5/Itz9o 6y9gLNtQzwmSDioV8KhF85VmYInslhv5tUtMEppfdTLyX4SUKh8ftNIVmH9mXyRCZclSoa6IMd635 Jq1Pj2/Lp64tOzSvN5Y9zaiCc5FucXtB9SaWsgdmFuIFJpZWwgPHJpZWxAc3VycmllbC5jb20+iQE +BBMBAgAoBQJSLd2lAhsjBQkSzAMABgsJCAcDAgYVCAIJCgsEFgIDAQIeAQIXgAAKCRDOed6ShMTe g4PpB/0ZivKYFt0LaB22ssWUrBoeNWCP1NY/lkq2QbPhR3agLB7ZXI97PF2z/5QD9Fuy/FD/jddPx KRTvFCtHcEzTOcFjBmf52uqgt3U40H9GM++0IM0yHusd9EzlaWsbp09vsAV2DwdqS69x9RPbvE/Ne fO5subhocH76okcF/aQiQ+oj2j6LJZGBJBVigOHg+4zyzdDgKM+jp0bvDI51KQ4XfxV593OhvkS3z 3FPx0CE7l62WhWrieHyBblqvkTYgJ6dq4bsYpqxxGJOkQ47WpEUx6onH+rImWmPJbSYGhwBzTo0Mm G1Nb1qGPG+mTrSmJjDRxrwf1zjmYqQreWVSFEt26tBpSaWsgdmFuIFJpZWwgPHJpZWxAZmIuY29tP okBPgQTAQIAKAUCW5LbiAIbIwUJEswDAAYLCQgHAwIGFQgCCQoLBBYCAwECHgECF4AACgkQznneko TE3oOUEQgAsrGxjTC1bGtZyuvyQPcXclap11Ogib6rQywGYu6/Mnkbd6hbyY3wpdyQii/cas2S44N cQj8HkGv91JLVE24/Wt0gITPCH3rLVJJDGQxprHTVDs1t1RAbsbp0XTksZPCNWDGYIBo2aHDwErhI omYQ0Xluo1WBtH/UmHgirHvclsou1Ks9jyTxiPyUKRfae7GNOFiX99+ZlB27P3t8CjtSO831Ij0Ip QrfooZ21YVlUKw0Wy6Ll8EyefyrEYSh8KTm8dQj4O7xxvdg865TLeLpho5PwDRF+/mR3qi8CdGbkE c4pYZQO8UDXUN4S+pe0aTeTqlYw8rRHWF9TnvtpcNzZw== Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.54.1 (3.54.1-1.fc41) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Sender: riel@surriel.com On Mon, 2025-01-20 at 19:09 +0200, Nadav Amit wrote: >=20 > On 20/01/2025 18:11, Rik van Riel wrote: > >=20 > > What guarantees that the page reclaim path won't free > > the pages until after TLBSYNC has completed on the CPUs > > that kicked off asynchronous flushes with INVPLGB? >=20 > [ you make me lose my confidence, although I see nothing wrong ] >=20 > Freeing the pages must be done after the TLBSYNC. I did not imply it=20 > needs to be changed. >=20 > The page freeing (and reclaim) path is only initiated after=20 > arch_tlbbatch_flush() is completed. If no migration is initiated, > since=20 > we did not remove any tlbsync, it should be fine. >=20 > If migration was initiated, and some invlpgb's were already > initiated,=20 > then we need for correctness to initiate tlbsync before the task > might=20 > be scheduled on another core. That's exactly why adding tlbsync to=20 > switch_mm_irqs_off() is needed in such a case. This is the page reclaim code. The process that has those other pages mapped might be running on other CPUs simultaneously with the page reclaim code. Even if we were invalidating one of our own pages this way, there could be other threads in the same process, running while we are in the page reclaim code. --=20 All Rights Reversed.