From: Marc Zyngier marc.zyngier@arm.com
commit f72af90c3783d924337624659b43e2d36f1b36b4 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.
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 [ v4.4: Made changes to hyp.S instead and fixed registers ] Signed-off-by: Viresh Kumar viresh.kumar@linaro.org --- arch/arm64/kvm/hyp.S | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S index 8d3da858c257..8aa2ede8c999 100644 --- a/arch/arm64/kvm/hyp.S +++ b/arch/arm64/kvm/hyp.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> @@ -974,10 +975,11 @@ el1_sync: // Guest trapped into EL2 lsr x2, x1, #ESR_ELx_EC_SHIFT
cmp x2, #ESR_ELx_EC_HVC64 + ccmp x2, #ESR_ELx_EC_HVC32, #4, ne b.ne el1_trap
- mrs x3, vttbr_el2 // If vttbr is valid, the 64bit guest - cbnz x3, el1_trap // called HVC + mrs x3, vttbr_el2 // If vttbr is valid, the guest + cbnz x3, el1_hvc_guest // called HVC
/* Here, we're pretty sure the host called HVC. */ pop x2, x3 @@ -1003,6 +1005,20 @@ el1_sync: // Guest trapped into EL2 pop lr, xzr 2: 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: /* * x1: ESR