• Thomas Gleixner's avatar
    x86/speculation: Avoid __switch_to_xtra() calls · 5635d999
    Thomas Gleixner authored
    The TIF_SPEC_IB bit does not need to be evaluated in the decision to invoke
    __switch_to_xtra() when:
    
     - CONFIG_SMP is disabled
    
     - The conditional STIPB mode is disabled
    
    The TIF_SPEC_IB bit still controls IBPB in both cases so the TIF work mask
    checks might invoke __switch_to_xtra() for nothing if TIF_SPEC_IB is the
    only set bit in the work masks.
    
    Optimize it out by masking the bit at compile time for CONFIG_SMP=n and at
    run time when the static key controlling the conditional STIBP mode is
    disabled.
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    Reviewed-by: Ingo Molnar's avatarIngo Molnar <mingo@kernel.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Andy Lutomirski <luto@kernel.org>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Jiri Kosina <jkosina@suse.cz>
    Cc: Tom Lendacky <thomas.lendacky@amd.com>
    Cc: Josh Poimboeuf <jpoimboe@redhat.com>
    Cc: Andrea Arcangeli <aarcange@redhat.com>
    Cc: David Woodhouse <dwmw@amazon.co.uk>
    Cc: Tim Chen <tim.c.chen@linux.intel.com>
    Cc: Andi Kleen <ak@linux.intel.com>
    Cc: Dave Hansen <dave.hansen@intel.com>
    Cc: Casey Schaufler <casey.schaufler@intel.com>
    Cc: Asit Mallick <asit.k.mallick@intel.com>
    Cc: Arjan van de Ven <arjan@linux.intel.com>
    Cc: Jon Masters <jcm@redhat.com>
    Cc: Waiman Long <longman9394@gmail.com>
    Cc: Greg KH <gregkh@linuxfoundation.org>
    Cc: Dave Stewart <david.c.stewart@intel.com>
    Cc: Kees Cook <keescook@chromium.org>
    Cc: stable@vger.kernel.org
    Link: https://lkml.kernel.org/r/20181125185005.374062201@linutronix.de
    
    5635d999
process.h 1.07 KB