d1440b23c9
The pageattr code has a pattern repeated where it sets _PAGE_GLOBAL for present PTEs but clears it for non-present PTEs. The intention is to keep _PAGE_GLOBAL from getting confused with _PAGE_PROTNONE since _PAGE_GLOBAL is for present PTEs and _PAGE_PROTNONE is for non-present But, this pattern makes no sense. Effectively, it says, if you use the pageattr code, always set _PAGE_GLOBAL when _PAGE_PRESENT. canon_pgprot() will clear it if unsupported (because it masks the value with __supported_pte_mask) but we *always* set it. Even if canon_pgprot() did not filter _PAGE_GLOBAL, it would be OK. _PAGE_GLOBAL is ignored when CR4.PGE=0 by the hardware. This unconditional setting of _PAGE_GLOBAL is a problem when we have PTI and non-PTI and we want some areas to have _PAGE_GLOBAL and some not. This updated version of the code says: 1. Clear _PAGE_GLOBAL when !_PAGE_PRESENT 2. Never set _PAGE_GLOBAL implicitly 3. Allow _PAGE_GLOBAL to be in cpa.set_mask 4. Allow _PAGE_GLOBAL to be inherited from previous PTE Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Arjan van de Ven <arjan@linux.intel.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Dan Williams <dan.j.williams@intel.com> Cc: David Woodhouse <dwmw2@infradead.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Hugh Dickins <hughd@google.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Juergen Gross <jgross@suse.com> Cc: Kees Cook <keescook@google.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nadav Amit <namit@vmware.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-mm@kvack.org Link: http://lkml.kernel.org/r/20180406205502.86E199DA@viggo.jf.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.