[RFC PATCH 2/5] hw/intc/gicv3: add support for setting KVM vGIC maintenance IRQ

[Miguel Luis <miguel.luis@oracle.com>]

From: Haibo Xu <haibo.xu@linaro.org>

Use the VGIC maintenance IRQ if VHE is requested. As per the ARM GIC
Architecture Specification for GICv3 and GICv4 Arm strongly recommends that
maintenance interrupts are configured to use INTID 25 matching the
Server Base System Architecture (SBSA) recomendation.

Ref: https://lore.kernel.org/qemu-devel/49a4944e2f148c56938380b981afe154b7a8b7ee.1617281290.git.haibo.xu@linaro.org/

Signed-off-by: Haibo Xu <haibo.xu@linaro.org>
[Miguel Luis: avoid direct usage of helpers (_check_attr(); _access())]
Signed-off-by: Miguel Luis <miguel.luis@oracle.com>
---
 hw/arm/virt.c                      |  5 +++++
 hw/intc/arm_gicv3_common.c         |  1 +
 hw/intc/arm_gicv3_kvm.c            | 25 +++++++++++++++++++++++++
 include/hw/intc/arm_gicv3_common.h |  1 +
 4 files changed, 32 insertions(+)

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index b871350856..377181e009 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -759,6 +759,11 @@ static void create_gic(VirtMachineState *vms, MemoryRegion *mem)
             qdev_prop_set_uint32(vms->gic, "redist-region-count[1]",
                 MIN(smp_cpus - redist0_count, redist1_capacity));
         }
+
+        if (kvm_irqchip_in_kernel()) {
+            qdev_prop_set_bit(vms->gic, "has-virtualization-extensions",
+                              vms->virt);
+        }
     } else {
         if (!kvm_irqchip_in_kernel()) {
             qdev_prop_set_bit(vms->gic, "has-virtualization-extensions",
diff --git a/hw/intc/arm_gicv3_common.c b/hw/intc/arm_gicv3_common.c
index 351843db4a..e2a6ff1b49 100644
--- a/hw/intc/arm_gicv3_common.c
+++ b/hw/intc/arm_gicv3_common.c
@@ -563,6 +563,7 @@ static Property arm_gicv3_common_properties[] = {
     DEFINE_PROP_UINT32("revision", GICv3State, revision, 3),
     DEFINE_PROP_BOOL("has-lpi", GICv3State, lpi_enable, 0),
     DEFINE_PROP_BOOL("has-security-extensions", GICv3State, security_extn, 0),
+    DEFINE_PROP_BOOL("has-virtualization-extensions", GICv3State, virt_extn, 0),
     /*
      * Compatibility property: force 8 bits of physical priority, even
      * if the CPU being emulated should have fewer.
diff --git a/hw/intc/arm_gicv3_kvm.c b/hw/intc/arm_gicv3_kvm.c
index 3ca643ecba..ce924753bb 100644
--- a/hw/intc/arm_gicv3_kvm.c
+++ b/hw/intc/arm_gicv3_kvm.c
@@ -22,6 +22,7 @@
 #include "qemu/osdep.h"
 #include "qapi/error.h"
 #include "hw/intc/arm_gicv3_common.h"
+#include "hw/arm/virt.h"
 #include "qemu/error-report.h"
 #include "qemu/module.h"
 #include "sysemu/kvm.h"
@@ -803,6 +804,30 @@ static void kvm_arm_gicv3_realize(DeviceState *dev, Error **errp)
         return;
     }
 
+
+    if (s->virt_extn) {
+        /*
+         * Arm strongly recommends that maintenance interrupts are configured
+         * to use INTID 25. For more information, see Server Base System
+         * Architecture (SBSA)
+         */
+        uint32_t maint_irq = PPI(ARCH_GIC_MAINT_IRQ);
+
+        struct kvm_device_attr kdevattr = {
+            .group = KVM_DEV_ARM_VGIC_GRP_MAINT_IRQ,
+            .addr = (uint64_t)&maint_irq
+        };
+
+        if (!kvm_device_ioctl(s->dev_fd, KVM_GET_DEVICE_ATTR, &kdevattr)) {
+            error_setg(errp, "VGICv3 setting maintenance IRQ are not "
+                            "supported by this host kernel");
+            return;
+        }
+
+        kvm_device_ioctl(s->dev_fd, KVM_SET_DEVICE_ATTR, &kdevattr);
+    }
+
+
     gicv3_init_irqs_and_mmio(s, kvm_arm_gicv3_set_irq, NULL);
 
     for (i = 0; i < s->num_cpu; i++) {
diff --git a/include/hw/intc/arm_gicv3_common.h b/include/hw/intc/arm_gicv3_common.h
index ab5182a28a..91e1c1a45a 100644
--- a/include/hw/intc/arm_gicv3_common.h
+++ b/include/hw/intc/arm_gicv3_common.h
@@ -248,6 +248,7 @@ struct GICv3State {
     uint32_t revision;
     bool lpi_enable;
     bool security_extn;
+    bool virt_extn;
     bool force_8bit_prio;
     bool irq_reset_nonsecure;
     bool gicd_no_migration_shift_bug;
-- 
2.39.2