• Andrew Cooper's avatar
    x86/cpu: Fix SMAP check in PVOPS environments · 581b7f15
    Andrew Cooper authored
    There appears to be no formal statement of what pv_irq_ops.save_fl() is
    supposed to return precisely.  Native returns the full flags, while lguest and
    Xen only return the Interrupt Flag, and both have comments by the
    implementations stating that only the Interrupt Flag is looked at.  This may
    have been true when initially implemented, but no longer is.
    
    To make matters worse, the Xen PVOP leaves the upper bits undefined, making
    the BUG_ON() undefined behaviour.  Experimentally, this now trips for 32bit PV
    guests on Broadwell hardware.  The BUG_ON() is consistent for an individual
    build, but not consistent for all builds.  It has also been a sitting timebomb
    since SMAP support was introduced.
    
    Use native_save_fl() instead, which will obtain an accurate view of the AC
    flag.
    Signed-off-by: default avatarAndrew Cooper <andrew.cooper3@citrix.com>
    Reviewed-by: default avatarDavid Vrabel <david.vrabel@citrix.com>
    Tested-by: default avatarRusty Russell <rusty@rustcorp.com.au>
    Cc: Rusty Russell <rusty@rustcorp.com.au>
    Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
    Cc: <lguest@lists.ozlabs.org>
    Cc: Xen-devel <xen-devel@lists.xen.org>
    CC: stable@vger.kernel.org
    Link: http://lkml.kernel.org/r/1433323874-6927-1-git-send-email-andrew.cooper3@citrix.comSigned-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    581b7f15
common.c 35.7 KB