From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 44143C77B60 for ; Wed, 5 Apr 2023 11:10:15 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C571E6B0071; Wed, 5 Apr 2023 07:10:14 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C08C16B0072; Wed, 5 Apr 2023 07:10:14 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id AA8A06B0074; Wed, 5 Apr 2023 07:10:14 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 992086B0071 for ; Wed, 5 Apr 2023 07:10:14 -0400 (EDT) Received: from smtpin29.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 68D131A1162 for ; Wed, 5 Apr 2023 11:10:14 +0000 (UTC) X-FDA: 80647068348.29.60D4BB5 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf25.hostedemail.com (Postfix) with ESMTP id A6131A0016 for ; Wed, 5 Apr 2023 11:10:12 +0000 (UTC) Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=u8LvHGP+; spf=pass (imf25.hostedemail.com: domain of frederic@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=frederic@kernel.org; dmarc=pass (policy=none) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1680693012; a=rsa-sha256; cv=none; b=hWRbrnI9Bnl2+CKM3y8vnpbd3G2TTsW8aJVZqTd6TTXYtBkx8KwLrcffVvNfMlMiz5xiwl 2qhCaenuK17qRXHrz5C+Y5BNR3c+nloXQJhfjFDULFCSN31kkT/gE0Q6RfdTuv8Ao8cBnS go5l9YnYhy5vdzIMGSXR22ikHEm8jTg= ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=u8LvHGP+; spf=pass (imf25.hostedemail.com: domain of frederic@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=frederic@kernel.org; dmarc=pass (policy=none) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1680693012; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=8jxjwqamHL9KyHiNCNBZo4nz2RajfjwZWsFc2088VHU=; b=wOidVBum2iNRuQ9nTC7BYIc1W34sjXJ1FcDSGkactZnhTSOpqR+citR3e2vC3jnqu9slF+ 9nk00cVSqw6s79tm+iancj3satDa2KV3aHVnaUf/xmlAviIshFAbves7L6PQmJ03nuJ4+o Z0XMett4xqRNYDeKJDHwINMWXO2kbTs= Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 99FA663CB4; Wed, 5 Apr 2023 11:10:11 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 50CBBC433D2; Wed, 5 Apr 2023 11:10:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1680693010; bh=ooCH6+LbUpOMMrNQgOWug2YiY+jDptLepUBqEHzy38Y=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=u8LvHGP+e+G/tSvmxikKj2fPXrrk0+3vQGP+KsaklvN9YmbUCHGANHWv3q6iC5HtS fy9l0bjNgR3HG3KM+EASpjRNgn7dp0Q7ndpMhPFCq5T5lviAwsVYYN/imSlMEqcc7J Pi0w5XFSLGZbOcOsH4lPOKZHWzTs10xmPVp5WHoBvKxxjhceqhX9MI5gQG81P+MTe7 LUV9T7LzQ/XDpFte7PNV4zDO5W1rZBSwLnn10QDPGf1MrC31gIz37yW68z2ShgDqIe WrsUT0GI5Rjs9+Bf9sMLDspBq0Su2t5h8EXV4hbTo1QGErDk8Mc1BEdaH+mzYziPqY DTUnzQSCU4SjA== Date: Wed, 5 Apr 2023 13:10:07 +0200 From: Frederic Weisbecker To: Yair Podemsky Cc: linux@armlinux.org.uk, mpe@ellerman.id.au, npiggin@gmail.com, christophe.leroy@csgroup.eu, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, davem@davemloft.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, will@kernel.org, aneesh.kumar@linux.ibm.com, akpm@linux-foundation.org, peterz@infradead.org, arnd@arndb.de, keescook@chromium.org, paulmck@kernel.org, jpoimboe@kernel.org, samitolvanen@google.com, ardb@kernel.org, juerg.haefliger@canonical.com, rmk+kernel@armlinux.org.uk, geert+renesas@glider.be, tony@atomide.com, linus.walleij@linaro.org, sebastian.reichel@collabora.com, nick.hawkins@hpe.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, mtosatti@redhat.com, vschneid@redhat.com, dhildenb@redhat.com, alougovs@redhat.com Subject: Re: [PATCH 3/3] mm/mmu_gather: send tlb_remove_table_smp_sync IPI only to CPUs in kernel mode Message-ID: References: <20230404134224.137038-1-ypodemsk@redhat.com> <20230404134224.137038-4-ypodemsk@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Queue-Id: A6131A0016 X-Rspamd-Server: rspam01 X-Stat-Signature: 5ggdp3ki1f9qb8octkd7pthse8g3dwe4 X-HE-Tag: 1680693012-589440 X-HE-Meta: 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 mIqr1NcN bYLmP8/qrmxXwPob9W3YhoaAVitIgG/GVIl6fBHyVhKIixoVJfgH4n08IkaLF/g8nVVdGKReZfjmQb3aVDwgcGuYo4Tn9FBsyZfVa0ekBK5iUN9tMxhUUlkssV2bTr2tlQQMrD729LgN5ZsQa9RR4c1YUYMlHyMBQEXqMnAJj5SAhJc/56KkzoFxNHzksGNawndKENrkf3VYLJP/W5jZzDr+a0YxsnvBIF1ClKwWPIGmv0L0eo6J7rhby7bDFU43IBE5s1kfu4+Fq0tXRalDyw0elqmZyXnMVkO/xjfbYLO9JZIB0ocpSmkszMoHGiJe90hPIHc+XYRv6pNbOQfj4zcNOJQ4lI0l330EEhhAvQZSTaJ1r4HPH1/83A3dyY7Md2pSRBo6x5i1ZHOfRglK8EDyCMWc9bcP/+zgkTYmeeeub26rxd+e5sSeg3OCnk+E52pXh 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: On Wed, Apr 05, 2023 at 12:44:04PM +0200, Frederic Weisbecker wrote: > On Tue, Apr 04, 2023 at 04:42:24PM +0300, Yair Podemsky wrote: > > + int state = atomic_read(&ct->state); > > + /* will return true only for cpus in kernel space */ > > + return state & CT_STATE_MASK == CONTEXT_KERNEL; > > +} > > Also note that this doesn't stricly prevent userspace from being interrupted. > You may well observe the CPU in kernel but it may receive the IPI later after > switching to userspace. > > We could arrange for avoiding that with marking ct->state with a pending work bit > to flush upon user entry/exit but that's a bit more overhead so I first need to > know about your expectations here, ie: can you tolerate such an occasional > interruption or not? Bah, actually what can we do to prevent from that racy IPI? Not much I fear...