[4.9,V2,14/24] ARM: KVM: Add SMCCC_ARCH_WORKAROUND_1 fast handling

Message ID 20181107164402.9380-15-dave.long@linaro.org
State New
Headers show
Series
  • V4.9 backport of 32-bit arm spectre patches
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Commit Message

David Long Nov. 7, 2018, 4:43 p.m.
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>

---
 arch/arm/kvm/hyp/hyp-entry.S | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

-- 
2.17.1

Patch

diff --git a/arch/arm/kvm/hyp/hyp-entry.S b/arch/arm/kvm/hyp/hyp-entry.S
index 1bdd03014138..64d4a39f4b4b 100644
--- 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