Messages in this thread Patch in this message | | | Date | Thu, 25 Feb 2016 16:00:37 +0000 | From | Matt Fleming <> | Subject | Re: [tip:efi/core] x86/mm/pat: Use _PAGE_GLOBAL bit for EFI page table mappings |
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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 <matt@codeblueprint.co.uk> 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 <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk> --- 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
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