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 X-Spam-Level: X-Spam-Status: No, score=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 00E05C43331 for ; Tue, 24 Mar 2020 15:55:55 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id AD33E2076F for ; Tue, 24 Mar 2020 15:55:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=ziepe.ca header.i=@ziepe.ca header.b="MrGUEZ9I" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AD33E2076F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ziepe.ca Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 447496B0005; Tue, 24 Mar 2020 11:55:55 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3F8236B0008; Tue, 24 Mar 2020 11:55:55 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2E6E66B000A; Tue, 24 Mar 2020 11:55:55 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0170.hostedemail.com [216.40.44.170]) by kanga.kvack.org (Postfix) with ESMTP id 160606B0005 for ; Tue, 24 Mar 2020 11:55:55 -0400 (EDT) Received: from smtpin13.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 03F9E82499B9 for ; Tue, 24 Mar 2020 15:55:55 +0000 (UTC) X-FDA: 76630706670.13.offer62_339a4941f6304 X-HE-Tag: offer62_339a4941f6304 X-Filterd-Recvd-Size: 5597 Received: from mail-qk1-f194.google.com (mail-qk1-f194.google.com [209.85.222.194]) by imf15.hostedemail.com (Postfix) with ESMTP for ; Tue, 24 Mar 2020 15:55:54 +0000 (UTC) Received: by mail-qk1-f194.google.com with SMTP id l25so14864488qki.7 for ; Tue, 24 Mar 2020 08:55:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=WKfNG8umMlwkpQpy66f4+p/cJ7axBraMaD/gLOw+hwA=; b=MrGUEZ9IiQLdHGz08a8ugYDa8Kh9rXV8aSLNAnHozoNnLeKHJVRGMe9+8m1GlUnstf 5tQpZMpOzCfVJxw86gZz4WggoXB0Lk1BX8/uFnmjM+uCn92w4dRor82thwtliC5iP6y4 /VJADA5NAPnbZwi11s0UvCWYud5WVJaWD2G41vqNRnnaMZFarV6c/scEaRy4/utVW5io HuiW5m2mDE6YyHm6pmCHQqtyi6ePkAMcQR77qCpuFosHVAiGz+OrsD3/7tJilvvyxdrX +quF2ez8iVba7Sx8HThDueT1e16xa52eSqf8BciD/j7h9YlZibh9+FT85mFcIKgSVAjO +Ahw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=WKfNG8umMlwkpQpy66f4+p/cJ7axBraMaD/gLOw+hwA=; b=AOV48rCzC7JP4QCJ6OOE41gRgopH8xLgdrUOqnCUDti2N7OQYHNXZP6JW3a6de55ef /vxALhaNsABeJogdWByy5ZQEPcAQ3NzxOR3w7Tbv1BmWapEAfr4kxIP8bx5cpvA+cUav akDt+/CV+Iriqk9VMMeKsuGe4pVrsr5pVlLecD+YqzFB9YOwtWstISNE1t0hcqXgG88g oVIOsJ6yUmTx093fr/BGcdSoOltvrgNIV7olClVm0WdN1GygRogoTpDdcNXJfOGV3+pw G1lHbJbzODpL+VCS1wKalvYXPN7EJAYvptZUGqM8Yq6OE4DkGFesLpibOkhbJkFax+9S EviA== X-Gm-Message-State: ANhLgQ1DTHqH13a+dlgbVwNRp6HJToBKGQQ2PTzXWftmXLtaj37BvmR3 RS2UMk6yRnlUNJHjf66LTDtd1A== X-Google-Smtp-Source: ADFU+vuLBR4sW0l9XYEmX4X3U9KJJIggAbGvaXnj0Zmnvl3IhX2Vdun2/yaOWCfr3BoRN1vAtQoZlA== X-Received: by 2002:a37:a70e:: with SMTP id q14mr23857810qke.41.1585065353693; Tue, 24 Mar 2020 08:55:53 -0700 (PDT) Received: from ziepe.ca (hlfxns017vw-142-68-57-212.dhcp-dynamic.fibreop.ns.bellaliant.net. [142.68.57.212]) by smtp.gmail.com with ESMTPSA id v20sm12871207qth.10.2020.03.24.08.55.53 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 24 Mar 2020 08:55:53 -0700 (PDT) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1jGluC-0004gw-I1; Tue, 24 Mar 2020 12:55:52 -0300 Date: Tue, 24 Mar 2020 12:55:52 -0300 From: Jason Gunthorpe To: Mike Kravetz Cc: "Longpeng (Mike, Cloud Infrastructure Service Product Dept.)" , akpm@linux-foundation.org, kirill.shutemov@linux.intel.com, linux-kernel@vger.kernel.org, arei.gonglei@huawei.com, weidong.huang@huawei.com, weifuqiang@huawei.com, kvm@vger.kernel.org, linux-mm@kvack.org, Matthew Wilcox , Sean Christopherson , stable@vger.kernel.org Subject: Re: [PATCH v2] mm/hugetlb: fix a addressing exception caused by huge_pte_offset() Message-ID: <20200324155552.GK20941@ziepe.ca> References: <1582342427-230392-1-git-send-email-longpeng2@huawei.com> <51a25d55-de49-4c0a-c994-bf1a8cfc8638@oracle.com> <20200323160955.GY20941@ziepe.ca> <69055395-e7e5-a8e2-7f3e-f61607149318@oracle.com> <20200323180706.GC20941@ziepe.ca> <88698dd7-eb87-4b0b-7ba7-44ef6eab6a6c@oracle.com> <20200323225225.GF20941@ziepe.ca> <20200324115541.GH20941@ziepe.ca> <98d35563-8af0-2693-7e76-e6435da0bbee@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <98d35563-8af0-2693-7e76-e6435da0bbee@oracle.com> User-Agent: Mutt/1.9.4 (2018-02-28) 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 Tue, Mar 24, 2020 at 08:25:09AM -0700, Mike Kravetz wrote: > On 3/24/20 4:55 AM, Jason Gunthorpe wrote: > > Also, since CH moved all the get_user_pages_fast code out of the > > arch's many/all archs can drop their arch specific version of this > > routine. This is really just a specialized version of gup_fast's > > algorithm.. > > > > (also the arch versions seem different, why do some return actual > > ptes, not null?) > > Not sure I understand that last question. The return value should be > a *pte or null. I mean the common code ends like this: pmd = pmd_offset(pud, addr); if (sz != PMD_SIZE && pmd_none(*pmd)) return NULL; /* hugepage or swap? */ if (pmd_huge(*pmd) || !pmd_present(*pmd)) return (pte_t *)pmd; return NULL; So it always returns a pointer into a PUD or PMD, while say, ppc in __find_linux_pte() ends like: return pte_offset_kernel(&pmd, ea); Which is pointing to a PTE So does sparc: pmd = pmd_offset(pud, addr); if (pmd_none(*pmd)) return NULL; if (is_hugetlb_pmd(*pmd)) return (pte_t *)pmd; return pte_offset_map(pmd, addr); Which is even worse because it is leaking a kmap.. etc > /* > * huge_pte_offset() - Walk the page table to resolve the hugepage > * entry at address @addr > * > * Return: Pointer to page table or swap entry (PUD or PMD) for ^^^^^^^^^^^^^^^^^^^ Ie the above is not followed by the archs I'm also scratching my head that a function that returns a pte_t * always returns a PUD or PMD. Strange bit of type casting.. Jason