1. Jan 24, 2013
  2. Jan 20, 2013
    • H. Peter Anvin's avatar
      x86-32: Start out cr0 clean, disable paging before modifying cr3/4 · 021ef050
      H. Peter Anvin authored
      Patch
      
        5a5a51db
      
       x86-32: Start out eflags and cr4 clean
      
      ... made x86-32 match x86-64 in that we initialize %eflags and %cr4
      from scratch.  This broke OLPC XO-1.5, because the XO enters the
      kernel with paging enabled, which the kernel doesn't expect.
      
      Since we no longer support 386 (the source of most of the variability
      in %cr0 configuration), we can simply match further x86-64 and
      initialize %cr0 to a fixed value -- the one variable part remaining in
      %cr0 is for FPU control, but all that is handled later on in
      initialization; in particular, configuring %cr0 as if the FPU is
      present until proven otherwise is correct and necessary for the probe
      to work.
      
      To deal with the XO case sanely, explicitly disable paging in %cr0
      before we muck with %cr3, %cr4 or EFER -- those operations are
      inherently unsafe with paging enabled.
      
      NOTE: There is still a lot of 386-related junk in head_32.S which we
      can and should get rid of, however, this is intended as a minimal fix
      whereas the cleanup can be deferred to the next merge window.
      
      Reported-by: default avatarAndres Salomon <dilinger@queued.net>
      Tested-by: default avatarDaniel Drake <dsd@laptop.org>
      Link: http://lkml.kernel.org/r/50FA0661.2060400@linux.intel.com
      
      
      Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
      021ef050
  3. Jan 18, 2013
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