arm64: KVM: Add SMCCC_ARCH_WORKAROUND_1 fast handling

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.

Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S
index e4f37b9dd47c05eb6013db98383e5f0c6f1348ea..f36464bd57c5f23f2fef85a51efe9c4b033874f1 100644 (file)
--- a/arch/arm64/kvm/hyp/hyp-entry.S
+++ b/arch/arm64/kvm/hyp/hyp-entry.S
@@ -15,6 +15,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <linux/arm-smccc.h>
 #include <linux/linkage.h>
 
 #include <asm/alternative.h>
@@ -64,10 +65,11 @@ alternative_endif
        lsr     x0, x1, #ESR_ELx_EC_SHIFT
 
        cmp     x0, #ESR_ELx_EC_HVC64
+       ccmp    x0, #ESR_ELx_EC_HVC32, #4, ne
        b.ne    el1_trap
 
-       mrs     x1, vttbr_el2           // If vttbr is valid, the 64bit guest
-       cbnz    x1, el1_trap            // called HVC
+       mrs     x1, vttbr_el2           // If vttbr is valid, the guest
+       cbnz    x1, el1_hvc_guest       // called HVC
 
        /* Here, we're pretty sure the host called HVC. */
        ldp     x0, x1, [sp], #16
@@ -100,6 +102,20 @@ alternative_endif
 
        eret
 
+el1_hvc_guest:
+       /*
+        * Fastest possible path for ARM_SMCCC_ARCH_WORKAROUND_1.
+        * The workaround has already been applied on the host,
+        * so let's quickly get back to the guest. We don't bother
+        * restoring x1, as it can be clobbered anyway.
+        */
+       ldr     x1, [sp]                                // Guest's x0
+       eor     w1, w1, #ARM_SMCCC_ARCH_WORKAROUND_1
+       cbnz    w1, el1_trap
+       mov     x0, x1
+       add     sp, sp, #16
+       eret
+
 el1_trap:
        /*
         * x0: ESR_EC