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Sat, 23 Jul 2022 09:17:02 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A94584C046; Sat, 23 Jul 2022 09:17:02 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id CB6064C044; Sat, 23 Jul 2022 09:17:01 +0000 (GMT) Received: from linux.ibm.com (unknown [9.145.2.93]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Sat, 23 Jul 2022 09:17:01 +0000 (GMT) Date: Sat, 23 Jul 2022 12:16:59 +0300 From: Mike Rapoport To: Nadav Amit Cc: linux-mm@kvack.org, Andrew Morton , Nadav Amit , Mike Kravetz , Hugh Dickins , Axel Rasmussen , Peter Xu , David Hildenbrand Subject: Re: [PATCH v2 2/5] userfaultfd: introduce access-likely mode for common operations Message-ID: References: <20220718114748.2623-1-namit@vmware.com> <20220718114748.2623-3-namit@vmware.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220718114748.2623-3-namit@vmware.com> X-TM-AS-GCONF: 00 X-Proofpoint-GUID: rvCuKV2HDDPi6SvohjiTg0cq54Dg97r8 X-Proofpoint-ORIG-GUID: q6G3OOPh2gyBtYaCRUAkkqMtNuSW8gxW X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.883,Hydra:6.0.517,FMLib:17.11.122.1 definitions=2022-07-22_06,2022-07-21_02,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 mlxscore=0 bulkscore=0 spamscore=0 impostorscore=0 lowpriorityscore=0 clxscore=1015 mlxlogscore=999 priorityscore=1501 suspectscore=0 phishscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2206140000 definitions=main-2207230040 ARC-Seal: i=1; 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dkim=pass header.d=ibm.com header.s=pp1 header.b=XzTOu7nt; dmarc=pass (policy=none) header.from=ibm.com; spf=pass (imf30.hostedemail.com: domain of rppt@linux.ibm.com designates 148.163.156.1 as permitted sender) smtp.mailfrom=rppt@linux.ibm.com X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 177E7800AD X-Stat-Signature: e7odzzajhs55skbqoj1t43m8yzjkjb4j X-Rspam-User: X-HE-Tag: 1658567829-747925 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, Jul 18, 2022 at 04:47:45AM -0700, Nadav Amit wrote: > From: Nadav Amit > > Introduce access-hints in userfaultfd. The expectation is that userspace > would set access-hints when a page-fault occurred on a page and would > not provide the access-hint on prefaulted memory. The exact behavior of > the kernel in regard to the hints would not be part of userfaultfd api. > > At this time the use of the access-hint is only in setting access-bit > similarly to the way it is done in do_set_pte(). In x86, currently PTEs > are always marked as young, including prefetched ones. But on arm64, > PTEs would be marked as old (when access bit is supported). > > If access hints are not enabled, the kernel would behave as if the > access-hint was provided for backward compatibility. > > Cc: Mike Kravetz > Cc: Hugh Dickins > Cc: Andrew Morton > Cc: Axel Rasmussen > Cc: Peter Xu > Cc: David Hildenbrand > Cc: Mike Rapoport > Signed-off-by: Nadav Amit > --- > fs/userfaultfd.c | 39 ++++++++++++++++++++++++++++---- > include/linux/userfaultfd_k.h | 1 + > include/uapi/linux/userfaultfd.h | 20 +++++++++++++++- > mm/internal.h | 13 +++++++++++ > mm/memory.c | 12 ---------- > mm/userfaultfd.c | 11 +++++++-- > 6 files changed, 77 insertions(+), 19 deletions(-) > > diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c > index 2ae24327beec..8d8792b27c53 100644 > --- a/fs/userfaultfd.c > +++ b/fs/userfaultfd.c > @@ -1708,13 +1708,21 @@ static int userfaultfd_copy(struct userfaultfd_ctx *ctx, > ret = -EINVAL; > if (uffdio_copy.src + uffdio_copy.len <= uffdio_copy.src) > goto out; > - if (uffdio_copy.mode & ~(UFFDIO_COPY_MODE_DONTWAKE|UFFDIO_COPY_MODE_WP)) > + if (uffdio_copy.mode & ~(UFFDIO_COPY_MODE_DONTWAKE|UFFDIO_COPY_MODE_WP| > + UFFDIO_COPY_MODE_ACCESS_LIKELY)) > goto out; > > mode_wp = uffdio_copy.mode & UFFDIO_COPY_MODE_WP; > > uffd_flags = mode_wp ? UFFD_FLAGS_WP : UFFD_FLAGS_NONE; > > + if (ctx->features & UFFD_FEATURE_ACCESS_HINTS) { > + if (uffdio_copy.mode & UFFDIO_COPY_MODE_ACCESS_LIKELY) > + uffd_flags |= UFFD_FLAGS_ACCESS_LIKELY; > + } else { > + uffd_flags |= UFFD_FLAGS_ACCESS_LIKELY; > + } > + This is quite a construct and it gets more complex in the following patches. How about making it to a static inline function? > if (mmget_not_zero(ctx->mm)) { > ret = mcopy_atomic(ctx->mm, uffdio_copy.dst, uffdio_copy.src, > uffdio_copy.len, &ctx->mmap_changing, > @@ -1765,9 +1773,17 @@ static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx, > if (ret) > goto out; > ret = -EINVAL; > - if (uffdio_zeropage.mode & ~UFFDIO_ZEROPAGE_MODE_DONTWAKE) > + if (uffdio_zeropage.mode & ~(UFFDIO_ZEROPAGE_MODE_DONTWAKE| > + UFFDIO_ZEROPAGE_MODE_ACCESS_LIKELY)) > goto out; > > + if (ctx->features & UFFD_FEATURE_ACCESS_HINTS) { > + if (uffdio_zeropage.mode & UFFDIO_ZEROPAGE_MODE_ACCESS_LIKELY) > + uffd_flags |= UFFD_FLAGS_ACCESS_LIKELY; > + } else { > + uffd_flags |= UFFD_FLAGS_ACCESS_LIKELY; > + } > + > if (mmget_not_zero(ctx->mm)) { > ret = mfill_zeropage(ctx->mm, uffdio_zeropage.range.start, > uffdio_zeropage.range.len, -- Sincerely yours, Mike.