From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 1830F3D7D70; Tue, 31 Mar 2026 21:11:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774991487; cv=none; b=O5oEulxG72aHu3u4IDv/yRioZl1ui9GjJlClRdTl5kgA4FMbNA3pcNo9ACEZ+nFIpoRVoLw8br6t4meGIvcBKO2/UU3loK1Khz1+o58mbHyOB7EOrMibx8P54qTgGwusZxdF+VuHZAi/ypEJQzsa8mN46SPVTrC5JkOSytcRoyM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774991487; c=relaxed/simple; bh=2zPP+LmYtyi//uMOzgdQ8fnlTThEckhI+esz3lXXfZ0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=rvE6fEikxYCSp359+X/Tuo4UuthigmKXJDxUr1bCkBwDueDPPUA8oGF31drNt+FyZdrU3OAJcqEDt+fgiszI/6toJafPqY+MlErZORiq5dFBJ2zajfu6ARmrJOgE8lhB9q2vncQe+QeZJwLYvUEvszFNmpY1EF+whO7DQbXGkfc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=A+6BW5OP; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="A+6BW5OP" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 51FF9C19423; Tue, 31 Mar 2026 21:11:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774991487; bh=2zPP+LmYtyi//uMOzgdQ8fnlTThEckhI+esz3lXXfZ0=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=A+6BW5OPP6fq/QKr9cgbG4pDUJxtSVWOEP2jOYcgkXDRXC2M6VOrRTy0xdXOH5tc6 DZXet3mOOqFZ3TTXsM4k3brhMAd33l0+ACPzw0ETx4EDl5Yd9M4Nk1XjkwyoMizldD muQqzHi3Mf5fbvq/Gy7m2Idm3tPgObuzN1km3ZSZkh7rW24eYdLSX41e+IAHkwRnG7 g/I/DrpgHad3VVIO3LWlyIJ0hy4UefQ/88lxbEphdhMSKYCoWYhGixnXRO+XmaVC5H KpBTWfcA9NIUxVJmYnU84LnD4K+KUFY9p2AxuhRW2vGQZTcS7V4oqeP3caEZoLMHt8 SxRZrFIdRVj2A== Message-ID: <665a19a0-47c2-404c-bd2b-482ab51b8f64@kernel.org> Date: Tue, 31 Mar 2026 23:11:22 +0200 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 1/2] mm: make lazy MMU mode context-aware To: Alexander Gordeev Cc: Kevin Brodsky , Andrew Morton , Gerald Schaefer , Heiko Carstens , Christian Borntraeger , Vasily Gorbik , linux-s390@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <44dd86c0-1845-4dd9-b4b4-2cef6d1c6357@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 3/25/26 17:20, Alexander Gordeev wrote: > On Wed, Mar 25, 2026 at 10:55:23AM +0100, David Hildenbrand (Arm) wrote: > > Hi David, > >>> +/** >>> + * lazy_mmu_mode_enable_pte() - Enable the lazy MMU mode with parameters >> >> You have to be a lot clearer about implications. For example, what >> happens if we would bail out and not process all ptes? What are the >> exact semantics. > > The only implication is "only this address/PTE range could be updated > and that range may span one page table at most". Probably phrase it stronger. "No ptes outside of this range must be updated" etc. > > Whether all or portion of PTEs were actually updated is not defined, > just like in case of lazy_mmu_mode_enable_pte(). Okay, then let's document that. > > Makes sense? > Yes. >>> + * Enters a new lazy MMU mode section; if the mode was not already enabled, >>> + * enables it and calls arch_enter_lazy_mmu_mode_pte(). >>> + * >>> + * Must be paired with a call to lazy_mmu_mode_disable(). >>> + * >>> + * Has no effect if called: >>> + * - While paused - see lazy_mmu_mode_pause() >>> + * - In interrupt context >>> + */ >>> +static inline void lazy_mmu_mode_enable_pte(struct mm_struct *mm, >>> + unsigned long addr, >>> + unsigned long end, >>> + pte_t *ptep) >> >> It can be multiple ptes, so should this be some kind of "pte_range"/ >> >> lazy_mmu_mode_enable_for_pte_range() >> >> A bit mouthful but clearer. >> >>> +{ >>> + struct lazy_mmu_state *state = ¤t->lazy_mmu_state; >>> + >>> + if (in_interrupt() || state->pause_count > 0) >>> + return; >>> + >>> + VM_WARN_ON_ONCE(state->enable_count == U8_MAX); >>> + >>> + if (state->enable_count++ == 0) >>> + arch_enter_lazy_mmu_mode_pte(mm, addr, end, ptep); > > I will also change arch_enter_lazy_mmu_mode_pte() to > arch_enter_lazy_mmu_mode_for_pte_range() then. > >>> +} >> >> I'm wondering whether that could instead be some optional interface that >> we trigger after the lazy_mmu_mode_enable. But looking at > > To me just two separate and (as you put it) mouthful names appeal better > than an optional follow-up interface. Yes, probably better. -- Cheers, David