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Date: Wed, 1 Nov 2017 11:46:31 -0700 From: Dave Hansen <dave.hansen@...ux.intel.com> To: Linus Torvalds <torvalds@...ux-foundation.org> Cc: Andy Lutomirski <luto@...nel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>, Kees Cook <keescook@...gle.com>, Hugh Dickins <hughd@...gle.com> Subject: Re: [PATCH 00/23] KAISER: unmap most of the kernel from userspace page tables On 11/01/2017 11:27 AM, Linus Torvalds wrote: > So I'd like to see not just the comments about this, but I'd like to > see the code itself actually making that very clear. Have *code* that > verifies that nobody ever tries to use this on a user address (because > that would *completely* screw up all coherency), but also I don't see > why the code possibly looks up the old physical address in ther page > table. Is there _any_ possible reason why you'd want to look up a page > from an old page table? As far as I can tell, we should always know > the physical page we are mapping a priori - we've never re-mapping > random virtual addresses or a highmem page or anything like that. > We're mapping the 1:1 kernel mapping only. The vmalloc()'d stacks definitely need the page table walk. That's yet another thing that will get simpler once we stop needing to map the process stacks. I think there was also a need to do this for the fixmap addresses for the GDT. But, I'm totally with you on making this stuff less generic.
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