libxl: fix migrate for HVM guests

Prior to 22909:6868f7f3ab3f libxl would loop waiting simultaneously
for the domain the acknowledge a PV suspend request (by clearing the
XenStore node) and for the domain to actually suspend. For HVM guests
without PV drivers this same loop was simply waiting for the domain to
suspend.

In 22909:6868f7f3ab3f the original loop was split into two loops
(first waiting for the acknowledgement and then for the actual
suspend). This caused libxl to incorrectly wait for an HVM guest
without PV drivers to acknowledge the XenStore request, which is not
something it would ever do.

Fix this by only waiting for an acknowledgement from a guest which
contains PV drivers.

Previously we were also making the request regardless of whether the
guest had PV drivers, change that to only make the request if the
guest has PV drivers.

Lastly there is no need to sample HVM_PARAM_ACPI_S_STATE twice and not
doing so simplifies the test for PVHVM vs. normal HVM guests.

Tested with:
	Windows with GPL PV drivers (event channel suspend mode)
	Windows without PV drivers (xc_domain_shutdown mode)
	Linux PV (PV with XenBus control node mode)
	Linux HVM (PVHVM with XenBus control node mode (*))
	Linux HVM (xc_domain_shutdown mode)

(*) In this case the kernel didn't actually suspend, due to:
	PM: Device input1 failed to suspend: error -22
	xen suspend: dpm_suspend_start -22
    which may be a misconfiguration in my setup or may be a kernel
    bug, but the libxl side dealt with this as gracefully as it could.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>

1 files changed, 60 insertions, 51 deletions

diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
index 7af00b2741..c702cf7cc5 100644
--- a/tools/libxl/libxl_dom.c
+++ b/tools/libxl/libxl_dom.c
@@ -345,16 +345,21 @@ static int libxl__domain_suspend_common_switch_qemu_logdirty(int domid, unsigned
 static int libxl__domain_suspend_common_callback(void *data)
 {
     struct suspendinfo *si = data;
-    unsigned long s_state = 0;
+    unsigned long hvm_s_state = 0, hvm_pvdrv = 0;
     int ret;
     char *path, *state = "suspend";
     int watchdog;
     libxl_ctx *ctx = libxl__gc_owner(si->gc);
     xs_transaction_t t;
 
-    if (si->hvm)
-        xc_get_hvm_param(ctx->xch, si->domid, HVM_PARAM_ACPI_S_STATE, &s_state);
-    if ((s_state == 0) && (si->suspend_eventchn >= 0)) {
+    if (si->hvm) {
+        xc_get_hvm_param(ctx->xch, si->domid, HVM_PARAM_CALLBACK_IRQ, &hvm_pvdrv);
+        xc_get_hvm_param(ctx->xch, si->domid, HVM_PARAM_ACPI_S_STATE, &hvm_s_state);
+    }
+
+    if ((hvm_s_state == 0) && (si->suspend_eventchn >= 0)) {
+        LIBXL__LOG(ctx, LIBXL__LOG_DEBUG, "issuing %s suspend request via event channel",
+                   si->hvm ? "PVHVM" : "PV");
         ret = xc_evtchn_notify(si->xce, si->suspend_eventchn);
         if (ret < 0) {
             LIBXL__LOG(ctx, LIBXL__LOG_ERROR, "xc_evtchn_notify failed ret=%d", ret);
@@ -368,64 +373,68 @@ static int libxl__domain_suspend_common_callback(void *data)
         si->guest_responded = 1;
         return 1;
     }
-    path = libxl__sprintf(si->gc, "%s/control/shutdown", libxl__xs_get_dompath(si->gc, si->domid));
-    libxl__xs_write(si->gc, XBT_NULL, path, "suspend");
-    if (si->hvm) {
-        unsigned long hvm_pvdrv, hvm_s_state;
-        xc_get_hvm_param(ctx->xch, si->domid, HVM_PARAM_CALLBACK_IRQ, &hvm_pvdrv);
-        xc_get_hvm_param(ctx->xch, si->domid, HVM_PARAM_ACPI_S_STATE, &hvm_s_state);
-        if (!hvm_pvdrv || hvm_s_state) {
-            LIBXL__LOG(ctx, LIBXL__LOG_DEBUG, "Calling xc_domain_shutdown on the domain");
-            xc_domain_shutdown(ctx->xch, si->domid, SHUTDOWN_suspend);
-        }
-    }
 
-    LIBXL__LOG(ctx, LIBXL__LOG_DEBUG, "wait for the guest to acknowledge suspend request");
-    watchdog = 60;
-    while (!strcmp(state, "suspend") && watchdog > 0) {
-        usleep(100000);
+    if (si->hvm && (!hvm_pvdrv || hvm_s_state)) {
+        LIBXL__LOG(ctx, LIBXL__LOG_DEBUG, "Calling xc_domain_shutdown on HVM domain");
+        xc_domain_shutdown(ctx->xch, si->domid, SHUTDOWN_suspend);
+        /* The guest does not (need to) respond to this sort of request. */
+        si->guest_responded = 1;
+    } else {
+        LIBXL__LOG(ctx, LIBXL__LOG_DEBUG, "issuing %s suspend request via XenBus control node",
+                   si->hvm ? "PVHVM" : "PV");
 
-        state = libxl__xs_read(si->gc, XBT_NULL, path);
+        path = libxl__sprintf(si->gc, "%s/control/shutdown", libxl__xs_get_dompath(si->gc, si->domid));
+        libxl__xs_write(si->gc, XBT_NULL, path, "suspend");
 
-        watchdog--;
-    }
+        LIBXL__LOG(ctx, LIBXL__LOG_DEBUG, "wait for the guest to acknowledge suspend request");
+        watchdog = 60;
+        while (!strcmp(state, "suspend") && watchdog > 0) {
+            usleep(100000);
 
-    /*
-     * Guest appears to not be responding. Cancel the suspend request.
-     *
-     * We re-read the suspend node and clear it within a transaction
-     * in order to handle the case where we race against the guest
-     * catching up and acknowledging the request at the last minute.
-     */
-    if (!strcmp(state, "suspend")) {
-        LIBXL__LOG(ctx, LIBXL__LOG_ERROR, "guest didn't acknowledge suspend, cancelling request");
-    retry_transaction:
-        t = xs_transaction_start(ctx->xsh);
+            state = libxl__xs_read(si->gc, XBT_NULL, path);
 
-        state = libxl__xs_read(si->gc, t, path);
+            watchdog--;
+        }
 
-        if (!strcmp(state, "suspend"))
-            libxl__xs_write(si->gc, t, path, "");
+        /*
+         * Guest appears to not be responding. Cancel the suspend
+         * request.
+         *
+         * We re-read the suspend node and clear it within a
+         * transaction in order to handle the case where we race
+         * against the guest catching up and acknowledging the request
+         * at the last minute.
+         */
+        if (!strcmp(state, "suspend")) {
+            LIBXL__LOG(ctx, LIBXL__LOG_ERROR, "guest didn't acknowledge suspend, cancelling request");
+        retry_transaction:
+            t = xs_transaction_start(ctx->xsh);
+
+            state = libxl__xs_read(si->gc, t, path);
+
+            if (!strcmp(state, "suspend"))
+                libxl__xs_write(si->gc, t, path, "");
+
+            if (!xs_transaction_end(ctx->xsh, t, 0))
+                if (errno == EAGAIN)
+                    goto retry_transaction;
 
-        if (!xs_transaction_end(ctx->xsh, t, 0))
-            if (errno == EAGAIN)
-                goto retry_transaction;
+        }
 
-    }
+        /*
+         * Final check for guest acknowledgement. The guest may have
+         * acknowledged while we were cancelling the request in which
+         * case we lost the race while cancelling and should continue.
+         */
+        if (!strcmp(state, "suspend")) {
+            LIBXL__LOG(ctx, LIBXL__LOG_ERROR, "guest didn't acknowledge suspend, request cancelled");
+            return 0;
+        }
 
-    /*
-     * Final check for guest acknowledgement. The guest may have
-     * acknowledged while we were cancelling the request in which case
-     * we lost the race while cancelling and should continue.
-     */
-    if (!strcmp(state, "suspend")) {
-        LIBXL__LOG(ctx, LIBXL__LOG_ERROR, "guest didn't acknowledge suspend, request cancelled");
-        return 0;
+        LIBXL__LOG(ctx, LIBXL__LOG_DEBUG, "guest acknowledged suspend request");
+        si->guest_responded = 1;
     }
 
-    LIBXL__LOG(ctx, LIBXL__LOG_DEBUG, "guest acknowledged suspend request");
-    si->guest_responded = 1;
-
     LIBXL__LOG(ctx, LIBXL__LOG_DEBUG, "wait for the guest to suspend");
     watchdog = 60;
     while (watchdog > 0) {