Patchwork [1/3] alleviate time drift with HPET periodic timers

login
register
mail settings
Submitter Ulrich Obergfell
Date March 18, 2011, 3:54 p.m.
Message ID <1379962083.421747.1300463688907.JavaMail.root@zmail07.collab.prod.int.phx2.redhat.com>
Download mbox | patch
Permalink /patch/87547/
State New
Headers show

Comments

Ulrich Obergfell - March 18, 2011, 3:54 p.m.
Part 1 of the patch implements the following QEMU command line option.

-hpet [device=none|present][,driftfix=none|slew]

Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Jan Kiszka - March 19, 2011, 9:45 a.m.
On 2011-03-18 16:54, Ulrich Obergfell wrote:
> 
> Part 1 of the patch implements the following QEMU command line option.
> 
> -hpet [device=none|present][,driftfix=none|slew]

Just define driftfix as property of the hpet device. That way it can be
controlled both globally (-global hpet.driftfix=...) and per hpet block
(once we support instantiating >1 of them).

Jan
Ulrich Obergfell - March 22, 2011, 9:40 a.m.
>> Part 1 of the patch implements the following QEMU command line option.
>>
>> -hpet [device=none|present][,driftfix=none|slew]
> 
> Just define driftfix as property of the hpet device. That way it can be
> controlled both globally (-global hpet.driftfix=...) and per hpet block
> (once we support instantiating >1 of them).


Many Thanks Jan,

I started investigating code changes. I'm thinking of ...

- adding a new field to the HPETState structure.

    uint32_t driftfix;

- adding the property 'driftfix' to the DeviceInfo structure.

    DEFINE_PROP_BIT("driftfix", HPETState, driftfix, 0, false)

  Using a single bit so that the option syntax would be, e.g.:

    -global hpet.driftfix=on     (Default is 'off')

- Replace all 'if (hpet_driftfix ...)' by:

    if ((HPETState)s->driftfix ...)


Regards,

Uli

Patch

diff -up ./qemu-config.c.orig1 ./qemu-config.c
--- ./qemu-config.c.orig1	2011-02-18 22:48:06.000000000 +0100
+++ ./qemu-config.c	2011-03-13 12:38:22.813976639 +0100
@@ -261,6 +261,23 @@  static QemuOptsList qemu_rtc_opts = {
     },
 };
 
+#ifdef CONFIG_HPET_DRIFTFIX
+static QemuOptsList qemu_hpet_opts = {
+    .name = "hpet",
+    .head = QTAILQ_HEAD_INITIALIZER(qemu_hpet_opts.head),
+    .desc = {
+        {
+            .name = "device",
+            .type = QEMU_OPT_STRING,
+        },{
+            .name = "driftfix",
+            .type = QEMU_OPT_STRING,
+        },
+        { /* end of list */ }
+    },
+};
+#endif
+
 static QemuOptsList qemu_global_opts = {
     .name = "global",
     .head = QTAILQ_HEAD_INITIALIZER(qemu_global_opts.head),
@@ -462,6 +479,9 @@  static QemuOptsList *vm_config_groups[32
     &qemu_netdev_opts,
     &qemu_net_opts,
     &qemu_rtc_opts,
+#ifdef CONFIG_HPET_DRIFTFIX
+    &qemu_hpet_opts,
+#endif
     &qemu_global_opts,
     &qemu_mon_opts,
     &qemu_cpudef_opts,
diff -up ./qemu-options.hx.orig1 ./qemu-options.hx
--- ./qemu-options.hx.orig1	2011-02-18 22:48:06.000000000 +0100
+++ ./qemu-options.hx	2011-03-13 12:38:22.815977096 +0100
@@ -972,6 +972,13 @@  STEXI
 Disable HPET support.
 ETEXI
 
+#ifdef CONFIG_HPET_DRIFTFIX
+DEF("hpet", HAS_ARG, QEMU_OPTION_hpet, \
+    "-hpet [device=none|present][,driftfix=none|slew]\n" \
+    "                disable or enable HPET, disable or enable drift fix for periodic timers\n",
+    QEMU_ARCH_ALL)
+#endif
+
 DEF("balloon", HAS_ARG, QEMU_OPTION_balloon,
     "-balloon none   disable balloon device\n"
     "-balloon virtio[,addr=str]\n"
diff -up ./vl.c.orig1 ./vl.c
--- ./vl.c.orig1	2011-02-18 22:48:06.000000000 +0100
+++ ./vl.c	2011-03-13 12:38:35.167984285 +0100
@@ -203,6 +203,9 @@  CharDriverState *parallel_hds[MAX_PARALL
 CharDriverState *virtcon_hds[MAX_VIRTIO_CONSOLES];
 int win2k_install_hack = 0;
 int rtc_td_hack = 0;
+#ifdef CONFIG_HPET_DRIFTFIX
+int hpet_driftfix = 0;
+#endif
 int usb_enabled = 0;
 int singlestep = 0;
 int smp_cpus = 1;
@@ -431,6 +434,41 @@  static void configure_rtc(QemuOpts *opts
     }
 }
 
+#ifdef CONFIG_HPET_DRIFTFIX
+static void configure_hpet(QemuOpts *opts)
+{
+    const char *value, *opt;
+
+    opt = "device";
+    value = qemu_opt_get(opts, opt);
+    if (value) {
+        if (!strcmp(value, "present")) {
+            no_hpet = 0;
+        } else if (!strcmp(value, "none")) {
+            no_hpet = 1;
+        } else {
+            goto error_exit;
+        }
+    }
+    opt = "driftfix";
+    value = qemu_opt_get(opts, opt);
+    if (value) {
+        if (!strcmp(value, "slew")) {
+            hpet_driftfix = 1;
+        } else if (!strcmp(value, "none")) {
+            hpet_driftfix = 0;
+        } else {
+            goto error_exit;
+        }
+    }
+    return;
+
+error_exit:
+    fprintf(stderr, "qemu: -hpet option '%s': value missing or invalid\n", opt);
+    exit(1);
+}
+#endif
+
 /***********************************************************/
 /* Bluetooth support */
 static int nb_hcis;
@@ -2644,6 +2682,15 @@  int main(int argc, char **argv, char **e
             case QEMU_OPTION_no_hpet:
                 no_hpet = 1;
                 break;
+#ifdef CONFIG_HPET_DRIFTFIX
+            case QEMU_OPTION_hpet:
+                opts = qemu_opts_parse(qemu_find_opts("hpet"), optarg, 0);
+                if (!opts) {
+                    exit(1);
+                }
+                configure_hpet(opts);
+                break;
+#endif
             case QEMU_OPTION_balloon:
                 if (balloon_parse(optarg) < 0) {
                     fprintf(stderr, "Unknown -balloon argument %s\n", optarg);