From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 255F22877DE; Fri, 31 Jul 2026 21:17:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785532652; cv=none; b=ZMKDb9eTLpG72UHNPrY5baMDreaNzYjbukAzcC1w+z4vv7i9/udGLGxd3krSiQhl7OTGAdg7x2PA1zNXv+MSmk/tCk8XosY7J6npdd6BfGMOLf8MfqMraBoqDqb9Q+euViLxY9N0SFHFtHbrotQw+1h6RAT0+ouKfOMCgT4ynWM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785532652; c=relaxed/simple; bh=6bxH2ahOGfDJCgo9iuZSyugLdWuxX1t3Tb3FewAdiPc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=stpUJYakAdF6Np7Ua6jbVeKw9yTDxn4mHbQoUqIV50SkSOIzuTJXVXREXrkUieeY2b1ee5oPgXh9213WPvnl7sdKLVWdyNUvQJnScXyDoARWUVlCGj8LYDo5asjUr0ad+8xKx6JTRSGWc8ZuyFxMoexeEcR/UyTpgiNpy/4+Bfg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DATojsrq; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="DATojsrq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1FEB01F00AC4; Fri, 31 Jul 2026 21:17:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785532650; bh=7WZzBzB5TcTM5WHmYQ8Q1dAbLhGvD103w+cLEBe4VuA=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=DATojsrqDUH2APrMK9JbylCWoE2ibRCU80F00dlXpjJ5tQnjcDpOyY3g1h5BaiXkh OPQFeTRsYckQ7zkJr8ySOqnEXtUPJ9duft5KOengcfVlj82GQ7OHLUYl/0APGURpbR InOeOg+Wkvj87hf1xVBgbm80Uvpy76xZ/d0vHtznzV505vzReXQHxpkJDoWCGw2BwK n+dgCmnoh3oGQ2+xsXY4mwgUvbCBCaqlbGSY1kPFCwF5fvZuxWlzKzyDR/rmE7RT2q LZ/Scw8myMGgEFz2/B1FpXBFZQ6957WjjFwwulg3XmXtT4VNTWJnUiMnJsb6tmcpDb QxHvmvGNGUzpw== Date: Fri, 31 Jul 2026 14:17:28 -0700 From: Wei Liu To: Andrew Morton Cc: Stanislav Kinsburskii , Jason Gunthorpe , Leon Romanovsky , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jonathan Corbet , Shuah Khan , Shuah Khan , "K. Y. Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Long Li , Lyude Paul , Danilo Krummrich , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Min Ma , Lizhi Hou , Oded Gabbay , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-hyperv@vger.kernel.org, dri-devel@lists.freedesktop.org, nouveau@lists.freedesktop.org, linux-rdma@vger.kernel.org Subject: Re: [PATCH v11 0/8] mm/hmm: Add mmap lock-drop support for userfaultfd-backed mappings Message-ID: <20260731211728.GA3243658@liuwe-devbox-debian-v2.local> References: <20260723-hmm-v10-v11-0-c55b003a4b61@gmail.com> <20260723142242.5d3f87208d47819d873ae458@linux-foundation.org> Precedence: bulk X-Mailing-List: linux-hyperv@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260723142242.5d3f87208d47819d873ae458@linux-foundation.org> On Thu, Jul 23, 2026 at 02:22:42PM -0700, Andrew Morton wrote: > On Thu, 23 Jul 2026 10:36:32 -0700 Stanislav Kinsburskii wrote: > > > This series extends the HMM framework to support userfaultfd-backed memory > > by allowing the mmap read lock to be dropped during hmm_range_fault(). > > > > Thanks, I've updated mm.git to this version. Hi Andrew, I see this series in linux-next now. I'm curious to know if these patches are going to make 7.3. We have some work that's dependent on this so would like to plan accordingly. Thank you Stanislav for continue pushing this. Thanks, Wei > > AI review suggests there may be some problems. Sorry, I don't recall if > these were considered in previous versions of the patchset: > > https://sashiko.dev/#/patchset/20260723-hmm-v10-v11-0-c55b003a4b61@gmail.com > > > > > Changes in v11: > > - Reject unstable address spaces in hmm_range_fault_unlocked_timeout() > > after taking mmap_lock and before walking page tables. > > - Compute the remaining HMM timeout budget before the time_after_eq() > > check in drm_gpusvm_get_pages() to make sure it can't result in zero > > and lead to infinite HMM range faulting loop. > > Here's how v11 altered mm.git: > > > drivers/gpu/drm/drm_gpusvm.c | 4 ++-- > mm/hmm.c | 6 ++++++ > 2 files changed, 8 insertions(+), 2 deletions(-) > > --- a/drivers/gpu/drm/drm_gpusvm.c~b > +++ a/drivers/gpu/drm/drm_gpusvm.c > @@ -1422,11 +1422,11 @@ int drm_gpusvm_get_pages(struct drm_gpus > struct dma_iova_state *state = &svm_pages->state; > > retry: > + remaining = timeout - jiffies; > + > if (time_after_eq(jiffies, timeout)) > return -EBUSY; > > - remaining = timeout - jiffies; > - > hmm_range.notifier_seq = mmu_interval_read_begin(notifier); > if (drm_gpusvm_pages_valid_unlocked(gpusvm, svm_pages)) > goto set_seqno; > --- a/mm/hmm.c~b > +++ a/mm/hmm.c > @@ -17,6 +17,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -806,6 +807,11 @@ int hmm_range_fault_unlocked_timeout(str > if (ret) > return ret; > > + if (check_stable_address_space(mm)) { > + mmap_read_unlock(mm); > + return -EFAULT; > + } > + > if (timeout && time_after(jiffies, deadline)) { > mmap_read_unlock(mm); > return -EBUSY; > _ >