From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matt Fleming Subject: [PATCH 03/40] x86/mm/pat: Document the (currently) EFI-only code path Date: Mon, 25 Apr 2016 21:06:35 +0100 Message-ID: <1461614832-17633-4-git-send-email-matt@codeblueprint.co.uk> References: <1461614832-17633-1-git-send-email-matt@codeblueprint.co.uk> Return-path: In-Reply-To: <1461614832-17633-1-git-send-email-matt@codeblueprint.co.uk> Sender: linux-kernel-owner@vger.kernel.org To: Ingo Molnar , Thomas Gleixner , "H . Peter Anvin" Cc: Matt Fleming , Ard Biesheuvel , linux-kernel@vger.kernel.org, linux-efi@vger.kernel.org, Andy Lutomirski , Borislav Petkov , Linus Torvalds , Sai Praneeth Prakhya List-Id: linux-efi@vger.kernel.org It's not at all obvious that populate_pgd() and friends are only executed when mapping EFI virtual memory regions or that no other pageattr callers pass a ->pgd value. Reported-by: Andy Lutomirski Cc: Borislav Petkov Cc: Sai Praneeth Prakhya Cc: Ingo Molnar Cc: Thomas Gleixner Cc: "H. Peter Anvin" Cc: Linus Torvalds Signed-off-by: Matt Fleming --- arch/x86/mm/pageattr.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index 01be9ec3bf79..a1f0e1d0ddc2 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -1125,8 +1125,14 @@ static int populate_pgd(struct cpa_data *cpa, unsigned long addr) static int __cpa_process_fault(struct cpa_data *cpa, unsigned long vaddr, int primary) { - if (cpa->pgd) + if (cpa->pgd) { + /* + * Right now, we only execute this code path when mapping + * the EFI virtual memory map regions, no other users + * provide a ->pgd value. This may change in the future. + */ return populate_pgd(cpa, vaddr); + } /* * Ignore all non primary paths. -- 2.7.3