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X-CSE-ConnectionGUID: VYO5eTQgQgSWLHO0uTdf1g== X-CSE-MsgGUID: nyNw2gJKRAmi/wiISM/PwA== X-IronPort-AV: E=McAfee;i="6700,10204,11292"; a="35498885" X-IronPort-AV: E=Sophos;i="6.12,251,1728975600"; d="scan'208";a="35498885" Received: from fmviesa010.fm.intel.com ([10.60.135.150]) by fmvoesa108.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Dec 2024 11:31:53 -0800 X-CSE-ConnectionGUID: puhYWLhrTxCkddI44a7G2Q== X-CSE-MsgGUID: ZOvVbemkRy6XjG3xptTdtg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.12,251,1728975600"; d="scan'208";a="98986706" Received: from jairdeje-mobl1.amr.corp.intel.com (HELO [10.124.221.219]) ([10.124.221.219]) by fmviesa010-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Dec 2024 11:31:52 -0800 Message-ID: <989b55cf-1f9e-4b73-b3dd-d8b6a62be3f2@intel.com> Date: Fri, 20 Dec 2024 11:31:51 -0800 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: [PATCH 00/10] Account page tables at all levels To: Kevin Brodsky , linux-mm@kvack.org Cc: Andrew Morton , Catalin Marinas , Dave Hansen , Linus Walleij , Andy Lutomirski , Peter Zijlstra , "Mike Rapoport (IBM)" , Ryan Roberts , Thomas Gleixner , Will Deacon , Matthew Wilcox , linux-alpha@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-kernel@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-openrisc@vger.kernel.org, linux-parisc@vger.kernel.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-um@lists.infradead.org, loongarch@lists.linux.dev, x86@kernel.org, Joerg Roedel References: <20241219164425.2277022-1-kevin.brodsky@arm.com> <765aec36-55a4-4161-bb30-4ff838bc2d98@arm.com> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 12/20/24 02:58, Kevin Brodsky wrote: >> One super tiny nit is that the PAE pgd _can_ be allocated using >> __get_free_pages(). It was originally there for Xen, but I think it's >> being used for PTI only at this point and the comments are wrong-ish. >> >> I kinda think we should just get rid of the 32-bit kmem_cache entirely. > That would certainly simplify things on the x86 side! I'm not at all > familiar with that code though, would you be happy with providing a > patch? I could add it to this series if that's convenient. I hacked this together yesterday: > https://git.kernel.org/pub/scm/linux/kernel/git/daveh/devel.git/log/?h=simplify-pae-20241220 It definitely needs some more work. I'm particularly still puzzling about why SHARED_KERNEL_PMD is used both as a trigger for 32b vs. PAGE_SIZE PAE pgd allocations _and_ for the actual PMD sharing. Xen definitely needed the whole page behavior but I'm not sure why PTI did. Either way, that series should make the PAE PGDs a _bit_ less weird at the cost of an extra ~2 pages per process for folks who are running 32-bit PAE kernels with PTI disabled. But I think the diffstat is worth it: 5 files changed, 16 insertions(+), 96 deletions(-)