On Wed, 24 Feb, at 08:39:56AM, Andy Lutomirski wrote: > > OK, although a comment might be nice.
Something like this? --- >From ac40fc0269d4d8cc9051982c177ee140d6e1b761 Mon Sep 17 00:00:00 2001 From: Matt Fleming <[email protected]> Date: Thu, 25 Feb 2016 15:54:50 +0000 Subject: [PATCH] x86/mm/pat: Document the (currently) EFI-only code path 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 <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Sai Praneeth Prakhya <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: "H. Peter Anvin" <[email protected]> Cc: Linus Torvalds <[email protected]> Signed-off-by: Matt Fleming <[email protected]> --- 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 14c38ae80409..8fee5b6f8f66 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. -- 2.6.2
