[PATCH 4.14 098/109] ARM: KVM: Add SMCCC_ARCH_WORKAROUND_1 fast handling

Greg Kroah-Hartman
2018-10-16T17:21:40Z

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
@@ -253,6 +254,20 @@ THUMB( orr lr, #1)
pop {r2, lr}
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