On Fri, Oct 16, 2015 at 04:20:27PM -0700, Sai Praneeth Prakhya wrote:
> From: Sai Praneeth <[email protected]>
>
> 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.
At least a comma and a "the" here:
"..., if it does not, the 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
do not
> hence when passed as arguments to __pa() kernel panics as reported by
> Dave Hansen here https://lkml.kernel.org/r/[email protected].
> 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 <[email protected]>
> Reported-by: Dave Hansen <[email protected]>
> Cc: Matt Fleming <[email protected]>
> Cc: Ricardo Neri <[email protected]>
> Cc: Glenn P Williamson <[email protected]>
> Cc: Ravi Shankar <[email protected]>
>
> 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.
> --
Looks ok to me, these minor nitpicks can be adjusted when applying, no
need to send another version.
Which brings me to the next question: Matt, are you picking this up or
should I?
If you, then
Reviewed-by: Borislav Petkov <[email protected]>
Thanks!
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
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