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 47B9EC7EE43 for ; Mon, 12 Jun 2023 21:27:32 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A51828E0003; Mon, 12 Jun 2023 17:27:31 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A01998E0002; Mon, 12 Jun 2023 17:27:31 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8F0648E0003; Mon, 12 Jun 2023 17:27:31 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 8088B8E0002 for ; Mon, 12 Jun 2023 17:27:31 -0400 (EDT) Received: from smtpin28.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 4ABD81C7C26 for ; Mon, 12 Jun 2023 21:27:31 +0000 (UTC) X-FDA: 80895382302.28.49FF22F Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf13.hostedemail.com (Postfix) with ESMTP id 5829B2000B for ; Mon, 12 Jun 2023 21:27:29 +0000 (UTC) Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=dacuBPoS; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf13.hostedemail.com: domain of sj@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=sj@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1686605249; a=rsa-sha256; cv=none; b=39sB43hfDGEWwn8wbwT08qtNMii7saO630YyUpOgbRWPJ+vGhO58MCX775fIKUy9saAd8W 6fs88SY+pffTJcP8yzecBHE+6RyQoU9lRwsEM0fCII17mbfbBi0z5mPaBacjk1OlLrT4FL Od6x1izVPqDhlcunaNaBBFVbN7ZDJew= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=dacuBPoS; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf13.hostedemail.com: domain of sj@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=sj@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1686605249; 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-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=35s0wI4i9zSZNHB8vRdbzCTKxCrc/UuNrjJTeVELBVQ=; b=RNsflYZ11UWfueAibNl8OKvc9ei7A8u0DE6exLDGHuQ2Ju7Tz3Avh6MGy+zVnRTN184j92 TqGOAu7yu9fKMZ9N+n1ZeViV/T/J2wseM9R7LQo8i2PxXIgJgMSs8bHXdxnWt5piMgTumX In3zLpN0tjPU8zRB7dfZiiacLQLGswk= 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 1E20D62AE7; Mon, 12 Jun 2023 21:27:28 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9BE59C433D2; Mon, 12 Jun 2023 21:27:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1686605247; bh=7LfNjfS4Zf4U5lMlQ2I09BVw2IXRjySt/jv0/P+rlX4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dacuBPoSFVDZwmysWY0+sJX2kCpLfzlOADMPWlPI1SXhY5oymB/CjE1k3GxRDWEvy +K68RJCTIWgm2AXWaHWcUrZeQzQSnCsu+OTNcTTgAHVbgq63G39+XV47Am+tCO4Y0Y xc9hxFjwncmMg/Twg/IsjTGVO87I/4PrZUqrl48TttOWMtN2d6vRlZoskBNffkVCJZ Z1GZRN5dZffADCi0q8aVKxHHhkX5HLiwjCbIGku1nIoQLs2+lxofK9jefoj0jetdPt twTY2rj6QVhglYyTNio8xUlTVQDpyJHbHRIi5Jb7iiTi/LUeoY3c/7Mk+b5X/cfkQS IAWgPT5j0O17Q== From: SeongJae Park To: Ryan Roberts Cc: "SeongJae Park" , "Matthew Wilcox (Oracle)" , "Kirill A. Shutemov" , "Mike Rapoport" , "Yu Zhao" , "Jason Gunthorpe" , "David Airlie" , "Daniel Vetter" , "Dimitri Sivanich" , "Alex Williamson" , "Oleksandr Tyshchenko" , "Alexander Viro" , "Christian Brauner" , "Mike Kravetz" , "Muchun Song" , "Mark Rutland" , "Alexander Shishkin" , "Jiri Olsa" , "Namhyung Kim" , "Ian Rogers" , "Adrian Hunter" , =?UTF-8?q?J=C3=A9r=C3=B4me=20Glisse?= , "Andrey Ryabinin" , "Alexander Potapenko" , "Andrey Konovalov" , "Dmitry Vyukov" , "Vincenzo Frascino" , "Johannes Weiner" , "Michal Hocko" , "Roman Gushchin" , "Shakeel Butt" , "Naoya Horiguchi" , "Miaohe Lin" , "Pasha Tatashin" , "Uladzislau Rezki" , "Christoph Hellwig" , "Lorenzo Stoakes" , linux-kernel@vger.kernel.org, linux-mm@kvack.org, damon@lists.linux.dev, kernel test robot Subject: Re: [PATCH v3 3/3] mm: ptep_get() conversion Date: Mon, 12 Jun 2023 21:27:23 +0000 Message-Id: <20230612212723.196693-1-sj@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230612151545.3317766-4-ryan.roberts@arm.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 5829B2000B X-Stat-Signature: cds3bs7uctf135odo9tt989s4ecexpmn X-HE-Tag: 1686605249-311744 X-HE-Meta: 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 L3iM7eC7 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 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 Mon, 12 Jun 2023 16:15:45 +0100 Ryan Roberts wrote: > Convert all instances of direct pte_t* dereferencing to instead use > ptep_get() helper. This means that by default, the accesses change from > a C dereference to a READ_ONCE(). This is technically the correct thing > to do since where pgtables are modified by HW (for access/dirty) they > are volatile and therefore we should always ensure READ_ONCE() > semantics. > > But more importantly, by always using the helper, it can be overridden > by the architecture to fully encapsulate the contents of the pte. Arch > code is deliberately not converted, as the arch code knows best. It is > intended that arch code (arm64) will override the default with its own > implementation that can (e.g.) hide certain bits from the core code, or > determine young/dirty status by mixing in state from another source. > > Conversion was done using Coccinelle: > > ---- > > // $ make coccicheck \ > // COCCI=ptepget.cocci \ > // SPFLAGS="--include-headers" \ > // MODE=patch > > virtual patch > > @ depends on patch @ > pte_t *v; > @@ > > - *v > + ptep_get(v) > > ---- > > Then reviewed and hand-edited to avoid multiple unnecessary calls to > ptep_get(), instead opting to store the result of a single call in a > variable, where it is correct to do so. This aims to negate any cost of > READ_ONCE() and will benefit arch-overrides that may be more complex. > > Included is a fix for an issue in an earlier version of this patch that > was pointed out by kernel test robot. The issue arose because config > MMU=n elides definition of the ptep helper functions, including > ptep_get(). HUGETLB_PAGE=n configs still define a simple > huge_ptep_clear_flush() for linking purposes, which dereferences the > ptep. So when both configs are disabled, this caused a build error > because ptep_get() is not defined. Fix by continuing to do a direct > dereference when MMU=n. This is safe because for this config the arch > code cannot be trying to virtualize the ptes because none of the ptep > helpers are defined. > > Reported-by: kernel test robot > Link: https://lore.kernel.org/oe-kbuild-all/202305120142.yXsNEo6H-lkp@intel.com/ > Signed-off-by: Ryan Roberts > --- > .../drm/i915/gem/selftests/i915_gem_mman.c | 8 +- > drivers/misc/sgi-gru/grufault.c | 2 +- > drivers/vfio/vfio_iommu_type1.c | 7 +- > drivers/xen/privcmd.c | 2 +- > fs/proc/task_mmu.c | 33 +++--- > fs/userfaultfd.c | 6 +- > include/linux/hugetlb.h | 4 + > include/linux/mm_inline.h | 2 +- > include/linux/pgtable.h | 6 +- > kernel/events/uprobes.c | 2 +- > mm/damon/ops-common.c | 2 +- > mm/damon/paddr.c | 2 +- > mm/damon/vaddr.c | 10 +- [...] > diff --git a/mm/damon/ops-common.c b/mm/damon/ops-common.c > index d4ab81229136..e940802a15a4 100644 > --- a/mm/damon/ops-common.c > +++ b/mm/damon/ops-common.c > @@ -39,7 +39,7 @@ struct folio *damon_get_folio(unsigned long pfn) > > void damon_ptep_mkold(pte_t *pte, struct vm_area_struct *vma, unsigned long addr) > { > - struct folio *folio = damon_get_folio(pte_pfn(*pte)); > + struct folio *folio = damon_get_folio(pte_pfn(ptep_get(pte))); > > if (!folio) > return; > diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c > index 5b3a3463d078..40801e38fcf0 100644 > --- a/mm/damon/paddr.c > +++ b/mm/damon/paddr.c > @@ -89,7 +89,7 @@ static bool __damon_pa_young(struct folio *folio, struct vm_area_struct *vma, > while (page_vma_mapped_walk(&pvmw)) { > addr = pvmw.address; > if (pvmw.pte) { > - *accessed = pte_young(*pvmw.pte) || > + *accessed = pte_young(ptep_get(pvmw.pte)) || > !folio_test_idle(folio) || > mmu_notifier_test_young(vma->vm_mm, addr); > } else { > diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c > index e814f66dfc2e..2fcc9731528a 100644 > --- a/mm/damon/vaddr.c > +++ b/mm/damon/vaddr.c > @@ -323,7 +323,7 @@ static int damon_mkold_pmd_entry(pmd_t *pmd, unsigned long addr, > walk->action = ACTION_AGAIN; > return 0; > } > - if (!pte_present(*pte)) > + if (!pte_present(ptep_get(pte))) > goto out; > damon_ptep_mkold(pte, walk->vma, addr); > out: > @@ -433,6 +433,7 @@ static int damon_young_pmd_entry(pmd_t *pmd, unsigned long addr, > unsigned long next, struct mm_walk *walk) > { > pte_t *pte; > + pte_t ptent; > spinlock_t *ptl; > struct folio *folio; > struct damon_young_walk_private *priv = walk->private; > @@ -471,12 +472,13 @@ static int damon_young_pmd_entry(pmd_t *pmd, unsigned long addr, > walk->action = ACTION_AGAIN; > return 0; > } > - if (!pte_present(*pte)) > + ptent = ptep_get(pte); > + if (!pte_present(ptent)) > goto out; > - folio = damon_get_folio(pte_pfn(*pte)); > + folio = damon_get_folio(pte_pfn(ptent)); > if (!folio) > goto out; > - if (pte_young(*pte) || !folio_test_idle(folio) || > + if (pte_young(ptent) || !folio_test_idle(folio) || > mmu_notifier_test_young(walk->mm, addr)) > priv->young = true; > *priv->folio_sz = folio_size(folio); For above DAMON part, Reviewed-by: SeongJae Park Thanks, SJ [...]