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Wed, 4 Dec 2024 17:46:36 +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 9Y4tJnyVUGdNHgAAD6G6ig (envelope-from ); Wed, 04 Dec 2024 17:46:36 +0000 Message-ID: Date: Wed, 4 Dec 2024 18:46:36 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: avoid zeroing user movable page twice with init_on_alloc=1 Content-Language: en-US To: Zi Yan , Matthew Wilcox Cc: Geert Uytterhoeven , linux-mm@kvack.org, Andrew Morton , David Hildenbrand , Miaohe Lin , Kefeng Wang , John Hubbard , "Huang, Ying" , Ryan Roberts , Alexander Potapenko , Kees Cook , linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org References: <20241011150304.709590-1-ziy@nvidia.com> <9942C08D-C188-461C-B731-F08DE294CD2B@nvidia.com> <09B2AB6A-B122-4287-B97E-F800E511097E@nvidia.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: <09B2AB6A-B122-4287-B97E-F800E511097E@nvidia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Action: no action X-Stat-Signature: eitbxsy3s6z6n35zbhk6qzc5z1ch8mjb X-Rspam-User: X-Rspamd-Queue-Id: D91E24001B X-Rspamd-Server: rspam08 X-HE-Tag: 1733334380-550031 X-HE-Meta: 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 HhYkF3IO HHlS1znHuNkTK8c5Ipf3OdazRHL+jNVrygbNurwnZVnbqwXzwbU9pU8FWMuyVf1//idJEv654THRoa0UT+d3uQFuM/xTSWhnhFA5p8LIc7LKR3Twu4KbckRyNp5Yczufc7fp7oPkUY/f7nH1exliOJ2B9YtNRGCS1cEMrZuZZjnvcKN7jlTV121jVn9IOwzPrTg3fvwAfEsINlM2ivB5RJm7FSLz2f8qvqu5BeROrTqiX0EnDEmZmS515gV0PyE7uYskQxJNPZuCUzX3oc2UanbXSmQgmCD47DmFbPmpexqk7cHmMcAk00N3NKmtlRWlfpuh1ovrIl5HBboD+K5H5ClPXEe6xyMjBh72Kx5s/6j8GLsY= 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: List-Subscribe: List-Unsubscribe: On 12/4/24 18:33, Zi Yan wrote: > On 4 Dec 2024, at 11:29, Matthew Wilcox wrote: > >> On Wed, Dec 04, 2024 at 11:16:51AM -0500, Zi Yan wrote: >>>> So maybe the clearing done as part of page allocator isn't enough here. >>>> >>> Basically, mips needs to flush data cache if kmap address is aliased to >> >> People use "aliased" in contronym ways. Do you mean "has a >> non-congruent alias" or "has a congruent alias"? >> >>> userspace address. This means when mips has THP on, the patch below >>> is not enough to fix the issue. >>> >>> In post_alloc_hook(), it does not make sense to pass userspace address >>> in to determine whether to flush dcache or not. >>> >>> One way to fix it is to add something like arch_userpage_post_alloc() >>> to flush dcache if kmap address is aliased to userspace address. >>> But my questions are that >>> 1) if kmap address will always be the same for two separate kmap_local() calls, >> >> No. It just takes the next address in the stack. > > Hmm, if kmap_local() gives different addresses, wouldn’t init_on_alloc be > causing issues before my patch? In the page allocator, the page is zeroed > from one kmap address without flush, then clear_user_highpage() clears > it again with another kmap address with flush. After returning to userspace, > the user application works on the page but when the cache line used by > init_on_alloc is written back (with 0s) at eviction, user data is corrupted. > Am I missing anything? Or all arch with cache aliasing never enables > init_on_alloc? Maybe the arch also defines some hooks like arch_kmap_local_post_unmap() ? As for the fix, could it rely on e.g. __HAVE_ARCH_COPY_USER_HIGHPAGE instead of CONFIG_MIPS? That affects more arches, I don't know if we broke only mips or others too. > Best Regards, > Yan, Zi