linux-kernel - [PATCH 4.9 49/59] ARM: KVM: Add SMCCC_ARCH_WORKAROUND

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Date:   Wed, 21 Nov 2018 20:07:04 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Russell King <rmk+kernel@...linux.org.uk>,
        Tony Lindgren <tony@...mide.com>,
        Marc Zyngier <marc.zyngier@....com>,
        "David A. Long" <dave.long@...aro.org>
Subject: [PATCH 4.9 49/59] ARM: KVM: Add SMCCC_ARCH_WORKAROUND_1 fast handling

4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: Russell King <rmk+kernel@...linux.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@...linux.org.uk>
Boot-tested-by: Tony Lindgren <tony@...mide.com>
Reviewed-by: Tony Lindgren <tony@...mide.com>
Reviewed-by: Marc Zyngier <marc.zyngier@....com>
Signed-off-by: David A. Long <dave.long@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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