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[70.27.3.10]) by smtp.gmail.com with ESMTPSA id v2-20020a05620a0f0200b006bb0e5ca4bbsm16343485qkl.85.2022.09.07.13.12.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 07 Sep 2022 13:12:18 -0700 (PDT) Date: Wed, 7 Sep 2022 16:12:16 -0400 From: Peter Xu To: Yang Shi Cc: david@redhat.com, kirill.shutemov@linux.intel.com, jhubbard@nvidia.com, jgg@nvidia.com, hughd@google.com, akpm@linux-foundation.org, aneesh.kumar@linux.ibm.com, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [v2 PATCH 2/2] powerpc/64s/radix: don't need to broadcast IPI for radix pmd collapse flush Message-ID: References: <20220907180144.555485-1-shy828301@gmail.com> <20220907180144.555485-2-shy828301@gmail.com> MIME-Version: 1.0 In-Reply-To: <20220907180144.555485-2-shy828301@gmail.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1662581542; a=rsa-sha256; cv=none; b=lrGjNU+c+YaoeNKj2IZIo+rEy0K8rq0JkV6gPwV8lSrFy71rBxFRKL/LytrNIS47UOnVqf kZhEGyZW0iVwK68Vobm4B8gaFKFNDZoiULpec7v+KyRLkYDl9U+PAS6fc8lWLsXqiVkEFr ODTLiGmEARhPOfs9m2nSB7pLuX0Vip0= ARC-Authentication-Results: i=1; imf11.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=bXsphSMD; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf11.hostedemail.com: domain of peterx@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=peterx@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1662581542; 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=PR8WUalLy9btDZgRxhhifmVZcWnjA5H+Lwe7MIcntxQ=; b=6DKacm5vBK81b+jVk9TFRSfg6sps96pAn2U9cPsa2xoW5IyMTaIn8QH87x6x4zhiMHlSIZ VEaqL6LWoj/YJvxLGPTH5+6wZWZf4Ur32YX1Gv8j3tpJCL9Ldpk1HFC0Gd1Wekl4oLrYo9 mm0riIw7drnzGxHDNkoMXszRfOqViS8= X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 5BCAD40068 Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=bXsphSMD; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf11.hostedemail.com: domain of peterx@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=peterx@redhat.com X-Stat-Signature: 6kexupcf4wbc8zqpju7y5j7fr75ktxdq X-Rspam-User: X-HE-Tag: 1662581542-798524 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, Sep 07, 2022 at 11:01:44AM -0700, Yang Shi wrote: > The IPI broadcast is used to serialize against fast-GUP, but fast-GUP > will move to use RCU instead of disabling local interrupts in fast-GUP. > Using an IPI is the old-styled way of serializing against fast-GUP > although it still works as expected now. > > And fast-GUP now fixed the potential race with THP collapse by checking > whether PMD is changed or not. So IPI broadcast in radix pmd collapse > flush is not necessary anymore. But it is still needed for hash TLB. > > Suggested-by: Aneesh Kumar K.V > Signed-off-by: Yang Shi Acked-by: Peter Xu -- Peter Xu