[RFC PATCH v5 04/52] i386/kvm: Add xen-version KVM accelerator property and init KVM Xen support

[David Woodhouse <dwmw2@infradead.org>]

From: David Woodhouse <dwmw@amazon.co.uk>

This just initializes the basic Xen support in KVM for now. Only permitted
on TYPE_PC_MACHINE because that's where the sysbus devices for Xen heap
overlay, event channel, grant tables and other stuff will exist. There's
no point having the basic hypercall support if nothing else works.

Provide sysemu/kvm_xen.h and a kvm_xen_get_caps() which will be used
later by support devices.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
---
 accel/kvm/kvm-all.c         |  1 +
 include/sysemu/kvm_int.h    |  2 ++
 include/sysemu/kvm_xen.h    | 20 +++++++++++++
 target/i386/kvm/kvm.c       | 59 +++++++++++++++++++++++++++++++++++++
 target/i386/kvm/meson.build |  2 ++
 target/i386/kvm/xen-emu.c   | 58 ++++++++++++++++++++++++++++++++++++
 target/i386/kvm/xen-emu.h   | 19 ++++++++++++
 7 files changed, 161 insertions(+)
 create mode 100644 include/sysemu/kvm_xen.h
 create mode 100644 target/i386/kvm/xen-emu.c
 create mode 100644 target/i386/kvm/xen-emu.h

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index f99b0becd8..568bb09c09 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -3620,6 +3620,7 @@ static void kvm_accel_instance_init(Object *obj)
     s->kvm_dirty_ring_size = 0;
     s->notify_vmexit = NOTIFY_VMEXIT_OPTION_RUN;
     s->notify_window = 0;
+    s->xen_version = 0;
 }
 
 /**
diff --git a/include/sysemu/kvm_int.h b/include/sysemu/kvm_int.h
index 3b4adcdc10..9a8c062609 100644
--- a/include/sysemu/kvm_int.h
+++ b/include/sysemu/kvm_int.h
@@ -110,6 +110,8 @@ struct KVMState
     struct KVMDirtyRingReaper reaper;
     NotifyVmexitOption notify_vmexit;
     uint32_t notify_window;
+    uint32_t xen_version;
+    uint32_t xen_caps;
 };
 
 void kvm_memory_listener_register(KVMState *s, KVMMemoryListener *kml,
diff --git a/include/sysemu/kvm_xen.h b/include/sysemu/kvm_xen.h
new file mode 100644
index 0000000000..296533f2d5
--- /dev/null
+++ b/include/sysemu/kvm_xen.h
@@ -0,0 +1,20 @@
+/*
+ * Xen HVM emulation support in KVM
+ *
+ * Copyright © 2019 Oracle and/or its affiliates. All rights reserved.
+ * Copyright © 2022 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#ifndef QEMU_SYSEMU_KVM_XEN_H
+#define QEMU_SYSEMU_KVM_XEN_H
+
+uint32_t kvm_xen_get_caps(void);
+
+#define kvm_xen_has_cap(cap) (!!(kvm_xen_get_caps() &           \
+                                 KVM_XEN_HVM_CONFIG_ ## cap))
+
+#endif /* QEMU_SYSEMU_KVM_XEN_H */
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index a213209379..b097de0524 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -31,6 +31,7 @@
 #include "sysemu/runstate.h"
 #include "kvm_i386.h"
 #include "sev.h"
+#include "xen-emu.h"
 #include "hyperv.h"
 #include "hyperv-proto.h"
 
@@ -41,6 +42,7 @@
 #include "qemu/error-report.h"
 #include "qemu/memalign.h"
 #include "hw/i386/x86.h"
+#include "hw/i386/pc.h"
 #include "hw/i386/apic.h"
 #include "hw/i386/apic_internal.h"
 #include "hw/i386/apic-msidef.h"
@@ -48,6 +50,8 @@
 #include "hw/i386/x86-iommu.h"
 #include "hw/i386/e820_memory_layout.h"
 
+#include "hw/xen/xen.h"
+
 #include "hw/pci/pci.h"
 #include "hw/pci/msi.h"
 #include "hw/pci/msix.h"
@@ -2513,6 +2517,22 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
         }
     }
 
+    if (s->xen_version) {
+#ifdef CONFIG_XEN_EMU
+        if (!object_dynamic_cast(OBJECT(ms), TYPE_PC_MACHINE)) {
+            error_report("kvm: Xen support only available in PC machine");
+            return -ENOTSUP;
+        }
+        ret = kvm_xen_init(s);
+        if (ret < 0) {
+            return ret;
+        }
+#else
+        error_report("kvm: Xen support not enabled in qemu");
+        return -ENOTSUP;
+#endif
+    }
+
     ret = kvm_get_supported_msrs(s);
     if (ret < 0) {
         return ret;
@@ -5706,6 +5726,36 @@ static void kvm_arch_set_notify_window(Object *obj, Visitor *v,
     s->notify_window = value;
 }
 
+static void kvm_arch_get_xen_version(Object *obj, Visitor *v,
+                                     const char *name, void *opaque,
+                                     Error **errp)
+{
+    KVMState *s = KVM_STATE(obj);
+    uint32_t value = s->xen_version;
+
+    visit_type_uint32(v, name, &value, errp);
+}
+
+static void kvm_arch_set_xen_version(Object *obj, Visitor *v,
+                                     const char *name, void *opaque,
+                                     Error **errp)
+{
+    KVMState *s = KVM_STATE(obj);
+    Error *error = NULL;
+    uint32_t value;
+
+    visit_type_uint32(v, name, &value, &error);
+    if (error) {
+        error_propagate(errp, error);
+        return;
+    }
+
+    s->xen_version = value;
+    if (value && xen_mode == XEN_DISABLED) {
+        xen_mode = XEN_EMULATE;
+    }
+}
+
 void kvm_arch_accel_class_init(ObjectClass *oc)
 {
     object_class_property_add_enum(oc, "notify-vmexit", "NotifyVMexitOption",
@@ -5722,6 +5772,15 @@ void kvm_arch_accel_class_init(ObjectClass *oc)
     object_class_property_set_description(oc, "notify-window",
                                           "Clock cycles without an event window "
                                           "after which a notification VM exit occurs");
+
+    object_class_property_add(oc, "xen-version", "uint32",
+                              kvm_arch_get_xen_version,
+                              kvm_arch_set_xen_version,
+                              NULL, NULL);
+    object_class_property_set_description(oc, "xen-version",
+                                          "Xen version to be emulated "
+                                          "(in XENVER_version form "
+                                          "e.g. 0x4000a for 4.10)");
 }
 
 void kvm_set_max_apic_id(uint32_t max_apic_id)
diff --git a/target/i386/kvm/meson.build b/target/i386/kvm/meson.build
index 736df8b72e..322272091b 100644
--- a/target/i386/kvm/meson.build
+++ b/target/i386/kvm/meson.build
@@ -7,6 +7,8 @@ i386_softmmu_kvm_ss.add(files(
   'kvm-cpu.c',
 ))
 
+i386_softmmu_kvm_ss.add(when: 'CONFIG_XEN_EMU', if_true: files('xen-emu.c'))
+
 i386_softmmu_kvm_ss.add(when: 'CONFIG_SEV', if_false: files('sev-stub.c'))
 
 i386_softmmu_ss.add(when: 'CONFIG_HYPERV', if_true: files('hyperv.c'), if_false: files('hyperv-stub.c'))
diff --git a/target/i386/kvm/xen-emu.c b/target/i386/kvm/xen-emu.c
new file mode 100644
index 0000000000..b556d903aa
--- /dev/null
+++ b/target/i386/kvm/xen-emu.c
@@ -0,0 +1,58 @@
+/*
+ * Xen HVM emulation support in KVM
+ *
+ * Copyright © 2019 Oracle and/or its affiliates. All rights reserved.
+ * Copyright © 2022 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "sysemu/kvm_int.h"
+#include "sysemu/kvm_xen.h"
+#include "kvm/kvm_i386.h"
+#include "xen-emu.h"
+
+int kvm_xen_init(KVMState *s)
+{
+    const int required_caps = KVM_XEN_HVM_CONFIG_HYPERCALL_MSR |
+        KVM_XEN_HVM_CONFIG_INTERCEPT_HCALL | KVM_XEN_HVM_CONFIG_SHARED_INFO;
+    struct kvm_xen_hvm_config cfg = {
+        .msr = XEN_HYPERCALL_MSR,
+        .flags = KVM_XEN_HVM_CONFIG_INTERCEPT_HCALL,
+    };
+    int xen_caps, ret;
+
+    xen_caps = kvm_check_extension(s, KVM_CAP_XEN_HVM);
+    if (required_caps & ~xen_caps) {
+        error_report("kvm: Xen HVM guest support not present or insufficient");
+        return -ENOSYS;
+    }
+
+    if (xen_caps & KVM_XEN_HVM_CONFIG_EVTCHN_SEND) {
+        struct kvm_xen_hvm_attr ha = {
+            .type = KVM_XEN_ATTR_TYPE_XEN_VERSION,
+            .u.xen_version = s->xen_version,
+        };
+        (void)kvm_vm_ioctl(s, KVM_XEN_HVM_SET_ATTR, &ha);
+
+        cfg.flags |= KVM_XEN_HVM_CONFIG_EVTCHN_SEND;
+    }
+
+    ret = kvm_vm_ioctl(s, KVM_XEN_HVM_CONFIG, &cfg);
+    if (ret < 0) {
+        error_report("kvm: Failed to enable Xen HVM support: %s",
+                     strerror(-ret));
+        return ret;
+    }
+
+    s->xen_caps = xen_caps;
+    return 0;
+}
+
+uint32_t kvm_xen_get_caps(void)
+{
+    return kvm_state->xen_caps;
+}
diff --git a/target/i386/kvm/xen-emu.h b/target/i386/kvm/xen-emu.h
new file mode 100644
index 0000000000..4f31bd96cb
--- /dev/null
+++ b/target/i386/kvm/xen-emu.h
@@ -0,0 +1,19 @@
+/*
+ * Xen HVM emulation support in KVM
+ *
+ * Copyright © 2019 Oracle and/or its affiliates. All rights reserved.
+ * Copyright © 2022 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#ifndef QEMU_I386_KVM_XEN_EMU_H
+#define QEMU_I386_KVM_XEN_EMU_H
+
+#define XEN_HYPERCALL_MSR 0x40000000
+
+int kvm_xen_init(KVMState *s);
+
+#endif /* QEMU_I386_KVM_XEN_EMU_H */
-- 
2.35.3