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[70.31.27.79]) by smtp.gmail.com with ESMTPSA id u184-20020a372ec1000000b006f9e103260dsm10617212qkh.91.2022.11.16.14.28.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 16 Nov 2022 14:28:51 -0800 (PST) Date: Wed, 16 Nov 2022 17:28:49 -0500 From: Peter Xu To: James Houghton Cc: Mike Kravetz , Muchun Song , David Hildenbrand , David Rientjes , Axel Rasmussen , Mina Almasry , Zach O'Keefe , Manish Mishra , Naoya Horiguchi , "Dr . David Alan Gilbert" , "Matthew Wilcox (Oracle)" , Vlastimil Babka , Baolin Wang , Miaohe Lin , Yang Shi , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH v2 33/47] userfaultfd: add UFFD_FEATURE_MINOR_HUGETLBFS_HGM Message-ID: References: <20221021163703.3218176-1-jthoughton@google.com> <20221021163703.3218176-34-jthoughton@google.com> MIME-Version: 1.0 In-Reply-To: <20221021163703.3218176-34-jthoughton@google.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=1668637734; a=rsa-sha256; cv=none; b=tfibssiiLKzu299KREjqoGVzf73+Nkhnj4xBVrNs2xdVYyKMykTFvjpabx8ifFjrLlXKJV HM3n5WxpNA7gCalr6ALZ1u+7NGfUnrMiyj5WP8Xv1WfPs4f3pu9PE4G3WPYoQ7gmKY3sYQ 9cJkZFMEOyVkZHVT6WqSnGWJtIzkZ0E= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b="daLRb3/2"; spf=pass (imf07.hostedemail.com: domain of peterx@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=peterx@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1668637734; 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=jvzvnWWvvncWVJBoG4PM/NRp2jE+Ki/mZmdWbCmPuG8=; b=ovobZkcnewB2DhoZjIdGKR0VjMs531+6zecW59H4TeRTer+AzQnR2o3Gb9Li5akG/3fmJ/ tohuy7Nd05Hf72W9efncedbb3dZI0tDimFjQV3FkvXTgunAjy4Ei2yDfLYYVfme5vyHxyu MWQVGPH4++36FG0iaJAhqIe9iAJ6NWk= X-Stat-Signature: t9etq39c4ajaawo548d9wzah3u3bnm5s X-Rspamd-Queue-Id: 86DA04000B Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b="daLRb3/2"; spf=pass (imf07.hostedemail.com: domain of peterx@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=peterx@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1668637734-519146 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 Fri, Oct 21, 2022 at 04:36:49PM +0000, James Houghton wrote: > Userspace must provide this new feature when it calls UFFDIO_API to > enable HGM. Userspace can check if the feature exists in > uffdio_api.features, and if it does not exist, the kernel does not > support and therefore did not enable HGM. > > Signed-off-by: James Houghton It's still slightly a pity that this can only be enabled by an uffd context plus a minor fault, so generic hugetlb users cannot directly leverage this. The patch itself looks good. -- Peter Xu