[v4.4,38/45] arm64: KVM: Add SMCCC_ARCH_WORKAROUND_1 fast handling

Message ID d46e18606161998259bad6926ffb0f388ebf9c27.1560480942.git.viresh.kumar@linaro.org
State New
Headers show
Series
  • V4.4 backport of arm64 Spectre patches
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Commit Message

Viresh Kumar June 14, 2019, 3:08 a.m.
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(-)

-- 
2.21.0.rc0.269.g1a574e7a288b

Patch

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