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h=Date:From:To:Cc:Subject:References:In-Reply-To; b=NDf5yNABuLUHiqeaxlPBpJIkI3TK9/rc8cWI+3xEERZ7V7seyLQhxFkrAmyfltW9A YMYkHArboRJpL/my33wJQzLLWU30oaoeEJ6Ttyg6w1/hv2TEYtTysufc1I4riY7Dqe 1JpKsL4Pz+cuPhrKS57RxOWMoKUh9ZXCcPFodVwYvHAdhk5Vs5zfob/oRkS22YVwvE 9ctwQ1+AqKOVimiiWzAVqs/TQgZg2HOTktggOfpLZh3Suk6syCfNKi0yyOR3e83vSz TLAmts2y/e750y5m0ukDcwHblMQiyyUtAMyxQ5Byvy5FEVfYT0tz5dLmFYwRCykPWh XLK7zvj4B1Wsw== Date: Tue, 8 Sep 2026 10:33:17 +0300 From: Mike Rapoport To: Kevin Brodsky Cc: linux-hardening@vger.kernel.org, Andrew Morton , Andy Lutomirski , Catalin Marinas , Dave Hansen , "David Hildenbrand (Arm)" , Jann Horn , Jeff Xu , Joey Gouly , Kees Cook , Linu Cherian , Linus Walleij , Marc Zyngier , Mark Brown , Matthew Wilcox , Maxwell Bland , Peter Zijlstra , Pierre Langlois , =?iso-8859-1?Q?Pierre-Cl=E9ment?= Tosi , Quentin Perret , Rick Edgecombe , Ryan Roberts , Vlastimil Babka , Will Deacon , Yang Shi , Yeoreum Yun , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, x86@kernel.org, Ira Weiny , Lorenzo Stoakes , Thomas Gleixner Subject: Re: [PATCH RFC v9 12/25] mm: kpkeys: Protect regular page tables Message-ID: References: <20260818-kpkeys-v9-0-743ad31b2c8f@arm.com> <20260818-kpkeys-v9-12-743ad31b2c8f@arm.com> <178877845406.3691569.12554855722197968629.b4-review@b4> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: DCF4B120008 X-Stat-Signature: 7q6mm3i1oru16if73f75n3igddr17mw1 X-HE-Tag: 1788852812-655927 X-HE-Meta: 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 Ecil7H36 Qb2hoDK/LMNjSajuu9dDMLWYgTSHTLXUs61Zs90yx5+6PNiC32/y8CutA/r5KQt9FobiG0zSXgW71hV8TD4NZ/lRZdxtyCG6WzdgMLjZf5aJuVdR9PbfUSDHieukNQ3iJiW0rkcaebkD27N2spRrwoNykfBd2mhp2zOCOx1QB540vwk4nFv1XO5px5ZHrBWIE0v7AvXj11wlkNeX+V5OsS0k1TlFYBNz1q/fXdtc47EcBGFo6XGtYDDEREp2QVjppfXcVkept8RcYxZTW5uUSYzVJ1Y9d3x1g//kJzZ9SDz3ovA3FZF53BEzefKQa4knLtmfiUkTpEo1gXngbipOfVUWANQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Sep 07, 2026 at 05:52:32PM +0200, Kevin Brodsky wrote: > On 07/09/2026 12:54, Mike Rapoport wrote: > >> [...] > >> > >> static inline struct ptdesc *pagetable_alloc_noprof(gfp_t gfp, unsigned int order) > >> { > >> - struct page *page = alloc_pages_noprof(gfp | __GFP_COMP, order); > >> + struct page *page; > >> + > >> + if (kpkeys_hardened_pgtables_enabled()) > >> + page = kpkeys_pgtable_alloc(gfp | __GFP_COMP, order); > >> + else > >> + page = alloc_pages_noprof(gfp | __GFP_COMP, order); > > Can we make it a sequence rahter than a branch? > > > > kpkeys_pgtable_alloc() does alloc_pages and then sets their pkeys, so I > > think something like this should work: > > > > page = alloc_pages_noprof(gfp | __GFP_COMP, order); > > if (!page) > > return NULL; > > err = kpkeys_pgtable_alloc(page); > > if (err) { > > __free_pages(page, order); > > return NULL; > > > > with if (kpkeys_hardened_pgtables_enabled()) folded into > > kpkeys_pgtable_alloc(). > > I agree this would be less ugly. In fact this is pretty much what this > series did up to RFC v5 (albeit in the ctor/dtor instead of alloc/free). > We could go back to this API, *but* the big issue is that it makes it > impossible to use a smarter allocation strategy for protected pages. > Patch 14 in RFC v6 [1] will give you an idea of what such an allocator > (with support for large blocks and splitting) would look like. > > As discussed with David H we're first trying to land this feature > without large block support (fully PTE-mapped direct map), but we do > want to support large blocks eventually [2] and I would prefer the core > API to be already compatible with that objective. Very happy to hear > about suggestions as to how to avoid the explicit condition in > pagetable_alloc() though! We could unconditionally replace alloc_pages_noprof() with kpkeys_pgtable_alloc() and make the latter choose the right allocator, but that's not very nice either :/ > - Kevin > > [1] > https://lore.kernel.org/linux-hardening/20260227175518.3728055-15-kevin.brodsky@arm.com/ > [2] https://lore.kernel.org/all/aMwd7IJVECEy8mzf@willie-the-truck/ -- Sincerely yours, Mike.