From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.223.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 31C7320BB3C; Fri, 25 Oct 2024 18:13:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=195.135.223.131 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729880011; cv=none; b=GfhM+IuwHtthdYlHhPWRByy0m4VNlnESb0nN1phVkchiohmxrNsPGNrtXPl0yCIiBJi4IERvfzlzShqmkS4MeV/RiBSLkpJmZLNQA1V31ZjNoPesZpbu9gHBeNoSbOeqx5rLHsU6IAOwWATy1pYBQjzFvPlODqKjb57IRAM/In4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729880011; c=relaxed/simple; bh=/PDztJNHx/avwMtJDa4GSCL4ZVfxliImRbrp3B3rzL8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Z+P85JE1LG8Rx56PoaB3cBxo9+PsF9DL13XKw1kfLYYSH9Z/KIRkqQ53cC7NToQlv5QgyFTPMcUteeubCi52DfGU/8l5lxzDj7hpEKtmCG66GXc2VQ9UDrfrzt1eOxme5X28DNYPE+tQiBPf8bjfYmOKLZEoYMC3VDOodrpavxQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz; spf=pass smtp.mailfrom=suse.cz; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b=Jnrff6cZ; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b=3NgZMXIE; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b=Jnrff6cZ; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b=3NgZMXIE; arc=none smtp.client-ip=195.135.223.131 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=suse.cz Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b="Jnrff6cZ"; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b="3NgZMXIE"; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b="Jnrff6cZ"; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b="3NgZMXIE" Received: from imap1.dmz-prg2.suse.org (unknown [10.150.64.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 011E31FE29; Fri, 25 Oct 2024 18:13:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1729880007; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=zKXJJEviamphxC/DA/8mSG5DEJnMjhmEflprXxZTXok=; b=Jnrff6cZgnegSXi9fKCBaBsAV7wjOxbBywa2Yrbp1Nc5KJ/20qOogMfdqgaUtE2nJye/H0 vHmQm2sPJgy9stbr1gTKHyF9ii3nypSNfDCQV+A8eC+chXVx42hP3AVoMa6/on5+EkBsqP ICKmUybNlTRppjoOCXYCLEtgUtFpHms= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1729880007; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=zKXJJEviamphxC/DA/8mSG5DEJnMjhmEflprXxZTXok=; b=3NgZMXIE3ZBeAqZQyJ3SQbfDyHo/PPltA0sQ3+akKvPcFgWPIOzY2jRut8HKSvH97pGqSI IZTwamiefcKK7LCw== Authentication-Results: smtp-out2.suse.de; none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1729880007; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=zKXJJEviamphxC/DA/8mSG5DEJnMjhmEflprXxZTXok=; b=Jnrff6cZgnegSXi9fKCBaBsAV7wjOxbBywa2Yrbp1Nc5KJ/20qOogMfdqgaUtE2nJye/H0 vHmQm2sPJgy9stbr1gTKHyF9ii3nypSNfDCQV+A8eC+chXVx42hP3AVoMa6/on5+EkBsqP ICKmUybNlTRppjoOCXYCLEtgUtFpHms= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1729880007; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=zKXJJEviamphxC/DA/8mSG5DEJnMjhmEflprXxZTXok=; b=3NgZMXIE3ZBeAqZQyJ3SQbfDyHo/PPltA0sQ3+akKvPcFgWPIOzY2jRut8HKSvH97pGqSI IZTwamiefcKK7LCw== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 7D347132D3; Fri, 25 Oct 2024 18:13:26 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id HFLaG8bfG2edIQAAD6G6ig (envelope-from ); Fri, 25 Oct 2024 18:13:26 +0000 Message-ID: <8b1854b5-5c0a-43b1-aed7-aa4e8b8e8a1a@suse.cz> Date: Fri, 25 Oct 2024 20:13:26 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/5] mm: pagewalk: add the ability to install PTEs Content-Language: en-US To: Lorenzo Stoakes , Andrew Morton Cc: Suren Baghdasaryan , "Liam R . Howlett" , Matthew Wilcox , "Paul E . McKenney" , Jann Horn , David Hildenbrand , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Muchun Song , Richard Henderson , Matt Turner , Thomas Bogendoerfer , "James E . J . Bottomley" , Helge Deller , Chris Zankel , Max Filippov , Arnd Bergmann , linux-alpha@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-arch@vger.kernel.org, Shuah Khan , Christian Brauner , linux-kselftest@vger.kernel.org, Sidhartha Kumar , Jeff Xu , Christoph Hellwig , linux-api@vger.kernel.org, John Hubbard References: <9be732fd0e897453116b433fe2f468ef7795602e.1729699916.git.lorenzo.stoakes@oracle.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJkBREIBQkRadznAAoJECJPp+fMgqZkNxIQ ALZRqwdUGzqL2aeSavbum/VF/+td+nZfuH0xeWiO2w8mG0+nPd5j9ujYeHcUP1edE7uQrjOC Gs9sm8+W1xYnbClMJTsXiAV88D2btFUdU1mCXURAL9wWZ8Jsmz5ZH2V6AUszvNezsS/VIT87 AmTtj31TLDGwdxaZTSYLwAOOOtyqafOEq+gJB30RxTRE3h3G1zpO7OM9K6ysLdAlwAGYWgJJ V4JqGsQ/lyEtxxFpUCjb5Pztp7cQxhlkil0oBYHkudiG8j1U3DG8iC6rnB4yJaLphKx57NuQ PIY0Bccg+r9gIQ4XeSK2PQhdXdy3UWBr913ZQ9AI2usid3s5vabo4iBvpJNFLgUmxFnr73SJ KsRh/2OBsg1XXF/wRQGBO9vRuJUAbnaIVcmGOUogdBVS9Sun/Sy4GNA++KtFZK95U7J417/J Hub2xV6Ehc7UGW6fIvIQmzJ3zaTEfuriU1P8ayfddrAgZb25JnOW7L1zdYL8rXiezOyYZ8Fm ZyXjzWdO0RpxcUEp6GsJr11Bc4F3aae9OZtwtLL/jxc7y6pUugB00PodgnQ6CMcfR/HjXlae h2VS3zl9+tQWHu6s1R58t5BuMS2FNA58wU/IazImc/ZQA+slDBfhRDGYlExjg19UXWe/gMcl De3P1kxYPgZdGE2eZpRLIbt+rYnqQKy8UxlszsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZAUSmwUJDK5EZgAKCRAiT6fnzIKmZOJGEACOKABgo9wJXsbWhGWYO7mD 8R8mUyJHqbvaz+yTLnvRwfe/VwafFfDMx5GYVYzMY9TWpA8psFTKTUIIQmx2scYsRBUwm5VI EurRWKqENcDRjyo+ol59j0FViYysjQQeobXBDDE31t5SBg++veI6tXfpco/UiKEsDswL1WAr tEAZaruo7254TyH+gydURl2wJuzo/aZ7Y7PpqaODbYv727Dvm5eX64HCyyAH0s6sOCyGF5/p eIhrOn24oBf67KtdAN3H9JoFNUVTYJc1VJU3R1JtVdgwEdr+NEciEfYl0O19VpLE/PZxP4wX PWnhf5WjdoNI1Xec+RcJ5p/pSel0jnvBX8L2cmniYnmI883NhtGZsEWj++wyKiS4NranDFlA HdDM3b4lUth1pTtABKQ1YuTvehj7EfoWD3bv9kuGZGPrAeFNiHPdOT7DaXKeHpW9homgtBxj 8aX/UkSvEGJKUEbFL9cVa5tzyialGkSiZJNkWgeHe+jEcfRT6pJZOJidSCdzvJpbdJmm+eED w9XOLH1IIWh7RURU7G1iOfEfmImFeC3cbbS73LQEFGe1urxvIH5K/7vX+FkNcr9ujwWuPE9b 1C2o4i/yZPLXIVy387EjA6GZMqvQUFuSTs/GeBcv0NjIQi8867H3uLjz+mQy63fAitsDwLmR EP+ylKVEKb0Q2A== In-Reply-To: <9be732fd0e897453116b433fe2f468ef7795602e.1729699916.git.lorenzo.stoakes@oracle.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Spam-Score: -4.30 X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; RCVD_TLS_ALL(0.00)[]; RCPT_COUNT_TWELVE(0.00)[31]; MID_RHS_MATCH_FROM(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com,gmx.de]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[google.com,oracle.com,infradead.org,kernel.org,redhat.com,kvack.org,vger.kernel.org,linux.dev,linaro.org,gmail.com,alpha.franken.de,HansenPartnership.com,gmx.de,zankel.net,chromium.org,nvidia.com]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; FUZZY_BLOCKED(0.00)[rspamd.com]; R_RATELIMIT(0.00)[to_ip_from(RL3py1j7x8bxoj6nr7eaeb97sq)] X-Spam-Flag: NO X-Spam-Level: On 10/23/24 18:24, Lorenzo Stoakes wrote: > The existing generic pagewalk logic permits the walking of page tables, > invoking callbacks at individual page table levels via user-provided > mm_walk_ops callbacks. > > This is useful for traversing existing page table entries, but precludes > the ability to establish new ones. > > Existing mechanism for performing a walk which also installs page table > entries if necessary are heavily duplicated throughout the kernel, each > with semantic differences from one another and largely unavailable for use > elsewhere. > > Rather than add yet another implementation, we extend the generic pagewalk > logic to enable the installation of page table entries by adding a new > install_pte() callback in mm_walk_ops. If this is specified, then upon > encountering a missing page table entry, we allocate and install a new one > and continue the traversal. > > If a THP huge page is encountered at either the PMD or PUD level we split > it only if there are ops->pte_entry() (or ops->pmd_entry at PUD level), > otherwise if there is only an ops->install_pte(), we avoid the unnecessary > split. > > We do not support hugetlb at this stage. > > If this function returns an error, or an allocation fails during the > operation, we abort the operation altogether. It is up to the caller to > deal appropriately with partially populated page table ranges. > > If install_pte() is defined, the semantics of pte_entry() change - this > callback is then only invoked if the entry already exists. This is a useful > property, as it allows a caller to handle existing PTEs while installing > new ones where necessary in the specified range. > > If install_pte() is not defined, then there is no functional difference to > this patch, so all existing logic will work precisely as it did before. > > As we only permit the installation of PTEs where a mapping does not already > exist there is no need for TLB management, however we do invoke > update_mmu_cache() for architectures which require manual maintenance of > mappings for other CPUs. > > We explicitly do not allow the existing page walk API to expose this > feature as it is dangerous and intended for internal mm use only. Therefore > we provide a new walk_page_range_mm() function exposed only to > mm/internal.h. > > Reviewed-by: Jann Horn > Signed-off-by: Lorenzo Stoakes Reviewed-by: Vlastimil Babka Just a small subjective suggestion in case you agree and there's a respin or followups: > @@ -109,18 +131,19 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end, > > if (walk->action == ACTION_AGAIN) > goto again; > - > - /* > - * Check this here so we only break down trans_huge > - * pages when we _need_ to > - */ > - if ((!walk->vma && (pmd_leaf(*pmd) || !pmd_present(*pmd))) || > - walk->action == ACTION_CONTINUE || > - !(ops->pte_entry)) > + if (walk->action == ACTION_CONTINUE) > continue; > + if (!ops->install_pte && !ops->pte_entry) > + continue; /* Nothing to do. */ > + if (!ops->pte_entry && ops->install_pte && > + pmd_present(*pmd) && > + (pmd_trans_huge(*pmd) || pmd_devmap(*pmd))) > + continue; /* Avoid unnecessary split. */ Much better now, thanks, but maybe the last 2 parts could be: if (!ops->pte_entry) { if (!ops->install_pte) continue; /* Nothing to do. */ else if (pmd_present(*pmd) && (pmd_trans_huge(*pmd) || pmd_devmap(*pmd))) continue; /* Avoid unnecessary split. */ } Or at least put !ops->pte_entry first in both conditions? > if (walk->vma) > split_huge_pmd(walk->vma, pmd, addr); > + else if (pmd_leaf(*pmd) || !pmd_present(*pmd)) > + continue; /* Nothing to do. */ > > err = walk_pte_range(pmd, addr, next, walk); > if (err) > @@ -148,11 +171,14 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end, > again: > next = pud_addr_end(addr, end); > if (pud_none(*pud)) { > - if (ops->pte_hole) > + if (ops->install_pte) > + err = __pmd_alloc(walk->mm, pud, addr); > + else if (ops->pte_hole) > err = ops->pte_hole(addr, next, depth, walk); > if (err) > break; > - continue; > + if (!ops->install_pte) > + continue; > } > > walk->action = ACTION_SUBTREE; > @@ -164,14 +190,20 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end, > > if (walk->action == ACTION_AGAIN) > goto again; > - > - if ((!walk->vma && (pud_leaf(*pud) || !pud_present(*pud))) || > - walk->action == ACTION_CONTINUE || > - !(ops->pmd_entry || ops->pte_entry)) > + if (walk->action == ACTION_CONTINUE) > continue; > + if (!ops->install_pte && !ops->pte_entry && !ops->pmd_entry) > + continue; /* Nothing to do. */ > + if (!ops->pmd_entry && !ops->pte_entry && ops->install_pte && > + pud_present(*pud) && > + (pud_trans_huge(*pud) || pud_devmap(*pud))) > + continue; /* Avoid unnecessary split. */ Ditto. Thanks!