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Date: Tue, 31 Oct 2017 17:21:56 -0700 From: Dave Hansen <dave.hansen@...el.com> To: Dave Hansen <dave.hansen@...ux.intel.com>, Linus Torvalds <torvalds@...ux-foundation.org>, Andy Lutomirski <luto@...nel.org> Cc: 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 10/31/2017 04:44 PM, Dave Hansen wrote: >> That seems insane. Why isn't only tyhe top level shadowed, and >> then lower levels are shared between the shadowed and the "kernel" >> page tables? > There are obviously two PGDs. The userspace half of the PGD is an exact > copy so all the lower levels are shared. You can see this bit in the > memcpy that we do in clone_pgd_range(). This is wrong. The userspace copying is done via the code we add to native_set_pgd(). Whenever we set the kernel PGD, we also make sure to make a corresponding entry in the user/shadow PGD. The memcpy() that I was talking about does the kernel portion of the PGD.
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