[Qemu-devel] [PATCH] hw/intc/arm_gicv3_kvm: Check KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS in reset

[Eric Auger <eric.auger@redhat.com>]

KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS needs to be checked before
attempting to read ICC_CTLR_EL1; otherwise kernel versions not
exposing this kvm device group will be incompatible with qemu 2.9.

Fixes: 07a5628  ("hw/intc/arm_gicv3_kvm: Reset GICv3 cpu interface registers")
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reported-by: Prakash B <bjsprakash.linux@gmail.com>

---

I understand the ICC_CTLR_EL1 state only is used in the put() function
which is used for migration
---
 hw/intc/arm_gicv3_kvm.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/hw/intc/arm_gicv3_kvm.c b/hw/intc/arm_gicv3_kvm.c
index 81f0403..4c3a88e 100644
--- a/hw/intc/arm_gicv3_kvm.c
+++ b/hw/intc/arm_gicv3_kvm.c
@@ -614,12 +614,6 @@ static void arm_gicv3_icc_reset(CPUARMState *env, const ARMCPRegInfo *ri)
     s = c->gic;
     cpu = ARM_CPU(c->cpu);
 
-    /* Initialize to actual HW supported configuration */
-    kvm_device_access(s->dev_fd, KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS,
-                      KVM_VGIC_ATTR(ICC_CTLR_EL1, cpu->mp_affinity),
-                      &c->icc_ctlr_el1[GICV3_NS], false);
-
-    c->icc_ctlr_el1[GICV3_S] = c->icc_ctlr_el1[GICV3_NS];
     c->icc_pmr_el1 = 0;
     c->icc_bpr[GICV3_G0] = GIC_MIN_BPR;
     c->icc_bpr[GICV3_G1] = GIC_MIN_BPR;
@@ -628,6 +622,17 @@ static void arm_gicv3_icc_reset(CPUARMState *env, const ARMCPRegInfo *ri)
     c->icc_sre_el1 = 0x7;
     memset(c->icc_apr, 0, sizeof(c->icc_apr));
     memset(c->icc_igrpen, 0, sizeof(c->icc_igrpen));
+
+    if (!kvm_device_check_attr(s->dev_fd, KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS,
+                              KVM_VGIC_ATTR(ICC_CTLR_EL1, cpu->mp_affinity))) {
+        return;
+    }
+    /* Initialize to actual HW supported configuration */
+    kvm_device_access(s->dev_fd, KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS,
+                      KVM_VGIC_ATTR(ICC_CTLR_EL1, cpu->mp_affinity),
+                      &c->icc_ctlr_el1[GICV3_NS], false);
+
+    c->icc_ctlr_el1[GICV3_S] = c->icc_ctlr_el1[GICV3_NS];
 }
 
 static void kvm_arm_gicv3_reset(DeviceState *dev)
-- 
2.5.5