* Toshi Kani <[email protected]> wrote:
> The following BUG_ON error was reported on QEMU/i386:
>
> kernel BUG at arch/x86/mm/physaddr.c:79!
> Call Trace:
> phys_mem_access_prot_allowed
> mmap_mem
> ? mmap_region
> mmap_region
> do_mmap
> vm_mmap_pgoff
> SyS_mmap_pgoff
> do_int80_syscall_32
> entry_INT80_32
>
> after commit edfe63ec97ed ("x86/mtrr: Fix Xorg crashes in
> Qemu sessions").
>
> PAT is now set to disabled state when MTRRs are disabled.
> Thus, reactivating the __pa(high_memory) check in
> phys_mem_access_prot_allowed().
>
> When CONFIG_DEBUG_VIRTUAL is set, __pa() calls __phys_addr(),
> which in turn calls slow_virt_to_phys() for 'high_memory'.
> Because 'high_memory' is set to (the max direct mapped virt
> addr + 1), it is not a valid virtual address. Hence,
> slow_virt_to_phys() returns 0 and hit the BUG_ON. Using
> __pa_nodebug() instead of __pa() will fix this BUG_ON.
>
> However, this code block, originally written for Pentiums and
> earlier, is no longer adequate since a 32-bit Xen guest has
> MTRRs disabled and supports ZONE_HIGHMEM. In this setup,
> this code sets UC attribute for accessing RAM in high memory
> range.
>
> Delete this code block as it has been unused for a long time.
>
> Reported-by: kernel test robot <[email protected]>
> Link: https://lkml.org/lkml/2016/4/1/608
> Signed-off-by: Toshi Kani <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: H. Peter Anvin <[email protected]>
> Cc: Borislav Petkov <[email protected]>
> Cc: David Vrabel <[email protected]>
So you missed the Reviewed-by tag from Boris ...
I've added it, but please try to propagate tags!
Thanks,
Ingo
