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  1. 11 Oct, 2007 1 commit
  2. 02 May, 2007 2 commits
  3. 07 Dec, 2006 1 commit
    • Chuck Ebbert's avatar
      [PATCH] i386: add sleazy FPU optimization · acc20761
      Chuck Ebbert authored
      i386 port of the sLeAZY-fpu feature.  Chuck reports that this gives him a +/-
      0.4% improvement on his simple benchmark
      
      x86_64 description follows:
      
      Right now the kernel on x86-64 has a 100% lazy fpu behavior: after *every*
      context switch a trap is taken for the first FPU use to restore the FPU
      context lazily.  This is of course great for applications that have very
      sporadic or no FPU use (since then you avoid doing the expensive save/restore
      all the time).  However for very frequent FPU users...  you take an extra trap
      every context switch.
      
      The patch below adds a simple heuristic to this code: After 5 consecutive
      context switches of FPU use, the lazy behavior is disabled and the context
      gets restored every context switch.  If the app indeed uses the FPU, the trap
      is avoided.  (the chance of the 6th time slice using FPU after the previous 5
      having done so are quite high obviously).
      
      After 256 switches, this is reset and lazy behavior is returned (until there
      are 5 consecutive ones again).  The reason for this is to give apps that do
      longer bursts of FPU use still the lazy behavior back after some time.
      Signed-off-by: default avatarChuck Ebbert <76306.1226@compuserve.com>
      Signed-off-by: default avatarArjan van de Ven <arjan@linux.intel.com>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarAndi Kleen <ak@suse.de>
      acc20761
  4. 29 Apr, 2006 1 commit
  5. 20 Apr, 2006 1 commit
    • Andi Kleen's avatar
      [PATCH] i386/x86-64: Fix x87 information leak between processes · 18bd057b
      Andi Kleen authored
      AMD K7/K8 CPUs only save/restore the FOP/FIP/FDP x87 registers in FXSAVE
      when an exception is pending.  This means the value leak through
      context switches and allow processes to observe some x87 instruction
      state of other processes.
      
      This was actually documented by AMD, but nobody recognized it as
      being different from Intel before.
      
      The fix first adds an optimization: instead of unconditionally
      calling FNCLEX after each FXSAVE test if ES is pending and skip
      it when not needed. Then do a x87 load from a kernel variable to
      clear FOP/FIP/FDP.
      
      This means other processes always will only see a constant value
      defined by the kernel in their FP state.
      
      I took some pain to make sure to chose a variable that's already
      in L1 during context switch to make the overhead of this low.
      
      Also alternative() is used to patch away the new code on CPUs
      who don't need it.
      
      Patch for both i386/x86-64.
      
      The problem was discovered originally by Jan Beulich. Richard
      Brunner provided the basic code for the workarounds, with contribution
      from Jan.
      
      This is CVE-2006-1056
      
      Cc: richard.brunner@amd.com
      Cc: jbeulich@novell.com
      Signed-off-by: default avatarAndi Kleen <ak@suse.de>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      18bd057b
  6. 12 Jan, 2006 1 commit
  7. 22 Jul, 2005 2 commits
    • Linus Torvalds's avatar
      x86: use alternative instructions for fnsave/fxsave too · 2847e347
      Linus Torvalds authored
      This one ends up using an inline asm format that claims to read memory
      and then clobber it (rather than just write it directly), which made it
      easier to use the existing "alternative_input()" infrastructure support.
      
      Now the fxsave code matches the fxrstor.
      2847e347
    • Linus Torvalds's avatar
      x86: make restore_fpu() use alternative assembler instructions · 8ed1383f
      Linus Torvalds authored
      It's really just a single instruction, conditional on whether the CPU
      supports FXSR or not, so implement it as such instead of making it a
      function that queries FXSR dynamically.
      
      This means that the instruction just gets automatically rewritten to the
      correct one at boot-time.
      8ed1383f
  8. 16 Apr, 2005 1 commit
    • Linus Torvalds's avatar
      Linux-2.6.12-rc2 · 1da177e4
      Linus Torvalds authored
      Initial git repository build. I'm not bothering with the full history,
      even though we have it. We can create a separate "historical" git
      archive of that later if we want to, and in the meantime it's about
      3.2GB when imported into git - space that would just make the early
      git days unnecessarily complicated, when we don't have a lot of good
      infrastructure for it.
      
      Let it rip!
      1da177e4