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    Subject[PATCH 4.9 49/59] ARM: KVM: Add SMCCC_ARCH_WORKAROUND_1 fast handling
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Russell King <rmk+kernel@armlinux.org.uk>

    Commit b800acfc70d9fb81fbd6df70f2cf5e20f70023d0 upstream.

    We want SMCCC_ARCH_WORKAROUND_1 to be fast. As fast as possible.
    So let's intercept it as early as we can by testing for the
    function call number as soon as we've identified a HVC call
    coming from the guest.

    Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
    Boot-tested-by: Tony Lindgren <tony@atomide.com>
    Reviewed-by: Tony Lindgren <tony@atomide.com>
    Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
    Signed-off-by: David A. Long <dave.long@linaro.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/arm/kvm/hyp/hyp-entry.S | 17 ++++++++++++++++-
    1 file changed, 16 insertions(+), 1 deletion(-)

    --- a/arch/arm/kvm/hyp/hyp-entry.S
    +++ b/arch/arm/kvm/hyp/hyp-entry.S
    @@ -16,6 +16,7 @@
    * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
    */

    +#include <linux/arm-smccc.h>
    #include <linux/linkage.h>
    #include <asm/kvm_arm.h>
    #include <asm/kvm_asm.h>
    @@ -202,7 +203,7 @@ hyp_hvc:
    lsr r2, r2, #16
    and r2, r2, #0xff
    cmp r2, #0
    - bne guest_trap @ Guest called HVC
    + bne guest_hvc_trap @ Guest called HVC

    /*
    * Getting here means host called HVC, we shift parameters and branch
    @@ -235,6 +236,20 @@ THUMB( orr lr, #1)
    pop {r2, lr}
    1: eret

    +guest_hvc_trap:
    + movw r2, #:lower16:ARM_SMCCC_ARCH_WORKAROUND_1
    + movt r2, #:upper16:ARM_SMCCC_ARCH_WORKAROUND_1
    + ldr r0, [sp] @ Guest's r0
    + teq r0, r2
    + bne guest_trap
    + add sp, sp, #12
    + @ Returns:
    + @ r0 = 0
    + @ r1 = HSR value (perfectly predictable)
    + @ r2 = ARM_SMCCC_ARCH_WORKAROUND_1
    + mov r0, #0
    + eret
    +
    guest_trap:
    load_vcpu r0 @ Load VCPU pointer to r0


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