From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sai Praneeth Prakhya Subject: [PATCH V2] x86/efi: Fix kernel panic when CONFIG_DEBUG_VIRTUAL is enabled Date: Fri, 16 Oct 2015 16:20:27 -0700 Message-ID: <1445037627-6488-1-git-send-email-sai.praneeth.prakhya@intel.com> Return-path: Sender: linux-efi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Cc: bp-Gina5bIWoIWzQB+pC5nmwQ@public.gmane.org, matt-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, dave.hansen-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, Sai Praneeth , Matt Fleming , Ricardo Neri , Glenn P Williamson , Ravi Shankar List-Id: linux-efi@vger.kernel.org From: Sai Praneeth When CONFIG_DEBUG_VIRTUAL is enabled, all accesses to __pa(address) are monitored to see whether address falls in direct mapping or kernel text mapping (see Documentation/x86/x86_64/mm.txt for details), if it does not kernel panics. During 1:1 mapping of EFI runtime services we access virtual addresses which are == physical addresses, thus the 1:1 mapping and these addresses donot fall in either of the above two regions and hence when passed as arguments to __pa() kernel panics as reported by Dave Hansen here https://lkml.kernel.org/r/5462999A.7090706-ral2JQCrhuFfmgfxC/sS/w@public.gmane.org So, before calling __pa() virtual addresses should be validated which results in skipping call to split_page_count() and that should be fine because it is used to keep track of everything *but* 1:1 mappings. Signed-off-by: Sai Praneeth Prakhya Reported-by: Dave Hansen Cc: Matt Fleming Cc: Ricardo Neri Cc: Glenn P Williamson Cc: Ravi Shankar Changes since v1: Made commit message more clear by adding reference to Documentation/x86/x86_64/mm.txt, instead of addresses "below 4G" changed it to "virtual addresses == physical addresses" quoted mail with k.org redirector and changed last line "to keep track of evrything *but* 1:1 mappings." Also made code more readable by adding a variable. --- arch/x86/mm/pageattr.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index 727158cb3b3c..9abe0c9b1098 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -648,9 +648,12 @@ __split_large_page(struct cpa_data *cpa, pte_t *kpte, unsigned long address, for (i = 0; i < PTRS_PER_PTE; i++, pfn += pfninc) set_pte(&pbase[i], pfn_pte(pfn, canon_pgprot(ref_prot))); - if (pfn_range_is_mapped(PFN_DOWN(__pa(address)), - PFN_DOWN(__pa(address)) + 1)) - split_page_count(level); + if (virt_addr_valid(address)) { + unsigned long pfn = PFN_DOWN(__pa(address)); + + if (pfn_range_is_mapped(pfn, pfn + 1)) + split_page_count(level); + } /* * Install the new, split up pagetable. -- 2.1.4