[Qemu-devel] [PATCH] Introduce -accel command option.

[anthony.perard@citrix.com]

From: Anthony PERARD <anthony.perard@citrix.com>

This option gives the ability to switch one "accelerator" like kvm, xen
or the default one tcg. We can specify more than one accelerator by
separate them by a comma. QEMU will try each one and use the first whose
works.

So,

-accel xen,kvm,tcg

which would try Xen support first, then KVM and finaly tcg if none of
the other works.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
---
 arch_init.c     |    5 +++
 arch_init.h     |    1 +
 qemu-options.hx |   10 ++++++
 vl.c            |   85 +++++++++++++++++++++++++++++++++++++++++++++++-------
 4 files changed, 90 insertions(+), 11 deletions(-)

diff --git a/arch_init.c b/arch_init.c
index 4486925..e0d7a4c 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -639,6 +639,11 @@ int audio_available(void)
 #endif
 }
 
+int tcg_available(void)
+{
+    return 1;
+}
+
 int kvm_available(void)
 {
 #ifdef CONFIG_KVM
diff --git a/arch_init.h b/arch_init.h
index 682890c..f0fb6a0 100644
--- a/arch_init.h
+++ b/arch_init.h
@@ -27,6 +27,7 @@ void do_acpitable_option(const char *optarg);
 void do_smbios_option(const char *optarg);
 void cpudef_init(void);
 int audio_available(void);
+int tcg_available(void);
 int kvm_available(void);
 int xen_available(void);
 
diff --git a/qemu-options.hx b/qemu-options.hx
index 4d99a58..958d126 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -1975,6 +1975,16 @@ Enable KVM full virtualization support. This option is only available
 if KVM support is enabled when compiling.
 ETEXI
 
+DEF("accel", HAS_ARG, QEMU_OPTION_accel, \
+    "-accel accel    use an accelerator (kvm,xen,tcg), default is tcg\n", QEMU_ARCH_ALL)
+STEXI
+@item -accel @var{accel}[,@var{accel}[,...]]
+@findex -accel
+This is use to enable an accelerator, in kvm,xen,tcg.
+By default, it use only tcg. If there a more than one accelerator
+specified, the next one is used if the first don't work.
+ETEXI
+
 DEF("xen-domid", HAS_ARG, QEMU_OPTION_xen_domid,
     "-xen-domid id   specify xen guest domain id\n", QEMU_ARCH_ALL)
 DEF("xen-create", 0, QEMU_OPTION_xen_create,
diff --git a/vl.c b/vl.c
index c58583d..2917e32 100644
--- a/vl.c
+++ b/vl.c
@@ -242,6 +242,7 @@ static void *boot_set_opaque;
 static NotifierList exit_notifiers =
     NOTIFIER_LIST_INITIALIZER(exit_notifiers);
 
+static int tcg_allowed = 1;
 int kvm_allowed = 0;
 uint32_t xen_domid;
 enum xen_mode xen_mode = XEN_EMULATE;
@@ -1723,6 +1724,72 @@ static int debugcon_parse(const char *devname)
     return 0;
 }
 
+static int tcg_init(int smp_cpus)
+{
+    return 0;
+}
+
+static struct {
+    const char *opt_name;
+    const char *name;
+    int (*available)(void);
+    int (*init)(int smp_cpus);
+    int *allowed;
+} accel_list[] = {
+    { "tcg", "tcg", tcg_available, tcg_init, &tcg_allowed },
+    { "kvm", "KVM", kvm_available, kvm_init, &kvm_allowed },
+};
+
+static int accel_parse_init(const char *opts)
+{
+    const char *p = opts;
+    char buf[10];
+    int i, ret;
+    bool accel_initalised = 0;
+    bool init_failed = 0;
+
+    while (!accel_initalised && *p != '\0') {
+        if (*p == ',') {
+            p++;
+        }
+        p = get_opt_name(buf, sizeof (buf), p, ',');
+        for (i = 0; i < ARRAY_SIZE(accel_list); i++) {
+            if (strcmp(accel_list[i].opt_name, buf) == 0) {
+                ret = accel_list[i].init(smp_cpus);
+                if (ret < 0) {
+                    init_failed = 1;
+                    if (!accel_list[i].available()) {
+                        printf("%s not supported for this target\n",
+                               accel_list[i].name);
+                    } else {
+                        fprintf(stderr, "failed to initialize %s: %s\n",
+                                accel_list[i].name,
+                                strerror(-ret));
+                    }
+                } else {
+                    accel_initalised = 1;
+                    *(accel_list[i].allowed) = 1;
+                }
+                break;
+            }
+        }
+        if (i == ARRAY_SIZE(accel_list)) {
+            fprintf(stderr, "\"%s\" accelerator does not exist.\n", buf);
+        }
+    }
+
+    if (!accel_initalised) {
+        fprintf(stderr, "No accelerator found!\n");
+        exit(1);
+    }
+
+    if (init_failed) {
+        fprintf(stderr, "Back to %s accelerator.\n", accel_list[i].name);
+    }
+
+    return !accel_initalised;
+}
+
 void qemu_add_exit_notifier(Notifier *notify)
 {
     notifier_list_add(&exit_notifiers, notify);
@@ -1802,6 +1869,7 @@ int main(int argc, char **argv, char **envp)
     const char *incoming = NULL;
     int show_vnc_port = 0;
     int defconfig = 1;
+    const char *accel_list_opts = "tcg";
 
 #ifdef CONFIG_SIMPLE_TRACE
     const char *trace_file = NULL;
@@ -2409,7 +2477,10 @@ int main(int argc, char **argv, char **envp)
                 do_smbios_option(optarg);
                 break;
             case QEMU_OPTION_enable_kvm:
-                kvm_allowed = 1;
+                accel_list_opts = "kvm";
+                break;
+            case QEMU_OPTION_accel:
+                accel_list_opts = optarg;
                 break;
             case QEMU_OPTION_usb:
                 usb_enabled = 1;
@@ -2719,16 +2790,8 @@ int main(int argc, char **argv, char **envp)
         exit(1);
     }
 
-    if (kvm_allowed) {
-        int ret = kvm_init(smp_cpus);
-        if (ret < 0) {
-            if (!kvm_available()) {
-                printf("KVM not supported for this target\n");
-            } else {
-                fprintf(stderr, "failed to initialize KVM: %s\n", strerror(-ret));
-            }
-            exit(1);
-        }
+    if (accel_list_opts) {
+        accel_parse_init(accel_list_opts);
     }
 
     if (qemu_init_main_loop()) {
-- 
1.7.1