[PATCH 4/4] Implement 'xm vcpu-set' command for HVM guest

[Anthony PERARD <anthony.perard@citrix.com>]

From: Ian Jackson <ian.jackson@eu.citrix.com>

Currently Xen has 'xm vcpu-set' command for PV domain, but not
available for HVM domain.  This patch is use to enable 'xm vcpu-set'
command for HVM domain. It setup vcpu watch at xenstore, and at qemu
side, handle vcpu online/offline accordingly.  With this patch, 'xm
vcpu-set' command works for both PV and HVM guest with same format.

Signed-off-by: Liu, Jinsong <jinsong.liu@intel.com>

Port from qemu-xen-traditionnal to qemu-xen:
  qemu-xen does not support anymore command through xenstore, so this
  path include an initialisation of a xenstore loop.
  An upstream of this patch would need to go QMP.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
---
 hw/acpi_piix4.c |  5 +++--
 xen-all.c       | 65 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+), 2 deletions(-)

diff --git a/hw/acpi_piix4.c b/hw/acpi_piix4.c
index 49c38d3..4c01aa2 100644
--- a/hw/acpi_piix4.c
+++ b/hw/acpi_piix4.c
@@ -728,8 +728,8 @@ static int disable_processor(PIIX4PMState *g, int cpu)
 
 void qemu_cpu_add_remove(int cpu, int state)
 {
-    if ((cpu <=0) || (cpu >= max_cpus)) {
-        fprintf(stderr, "vcpu out of range, should be [1~%d]\n", max_cpus - 1);
+    if ((cpu < 0) || (cpu >= max_cpus)) {
+        fprintf(stderr, "vcpu out of range, should be [0~%d]\n", max_cpus - 1);
         return;
     }
 
@@ -742,6 +742,7 @@ void qemu_cpu_add_remove(int cpu, int state)
             return;
         }
     }
+    fprintf(stderr, "%s vcpu %d\n", state ? "Add" : "Remove", cpu);
 
     pm_update_sci(acpi_state);
 }
diff --git a/xen-all.c b/xen-all.c
index daf43b9..04b88a6 100644
--- a/xen-all.c
+++ b/xen-all.c
@@ -99,6 +99,8 @@ typedef struct XenIOState {
     Notifier suspend;
 } XenIOState;
 
+static void xen_xenstore_watch_vcpu_set(XenIOState *state);
+
 /* Xen specific function for piix pci */
 
 int xen_pci_slot_get_pirq(PCIDevice *pci_dev, int irq_num)
@@ -1170,6 +1172,7 @@ int xen_hvm_init(void)
     xen_be_register("vkbd", &xen_kbdmouse_ops);
     xen_be_register("qdisk", &xen_blkdev_ops);
     xen_read_physmap(state);
+    xen_xenstore_watch_vcpu_set(state);
 
     return 0;
 }
@@ -1234,3 +1237,65 @@ void xen_modified_memory(ram_addr_t start, ram_addr_t length)
         }
     }
 }
+
+/* Xenstore watch init for vcpu-set */
+
+static void xenstore_process_vcpu_set_event(char **vec, struct xs_handle *xsh)
+{
+    char *act = NULL;
+    char *vcpustr, *node = vec[XS_WATCH_PATH];
+    unsigned int vcpu, len;
+
+    vcpustr = strstr(node, "cpu/");
+    if (!vcpustr) {
+        fprintf(stderr, "vcpu-set: watch node error.\n");
+        return;
+    }
+    sscanf(vcpustr, "cpu/%u", &vcpu);
+
+    act = xs_read(xsh, XBT_NULL, node, &len);
+    if (!act) {
+        fprintf(stderr, "vcpu-set: no command yet.\n");
+        return;
+    }
+
+    if (!strncmp(act, "online", len))
+        qemu_cpu_add_remove(vcpu, 1);
+    else if (!strncmp(act, "offline", len))
+        qemu_cpu_add_remove(vcpu, 0);
+    else
+        fprintf(stderr, "vcpu-set: command error.\n");
+
+    free(act);
+    return;
+}
+
+static void xenstore_process_event(void *opaque)
+{
+    char **vec;
+    unsigned int num;
+    struct xs_handle *xsh = opaque;
+
+    vec = xs_read_watch(xsh, &num);
+    if (!vec)
+        return;
+
+    if (!strcmp(vec[XS_WATCH_TOKEN], "vcpu-set")) {
+        xenstore_process_vcpu_set_event(vec, xsh);
+        goto out;
+    }
+
+ out:
+    free(vec);
+}
+
+static void xen_xenstore_watch_vcpu_set(XenIOState *state)
+{
+    char path[40];
+    /* Set a watch for vcpu-set */
+    snprintf(path, sizeof(path), "/local/domain/%d/cpu", xen_domid);
+    xs_watch(state->xenstore, path, "vcpu-set");
+
+    qemu_set_fd_handler(xs_fileno(state->xenstore), xenstore_process_event,
+                        NULL, state->xenstore);
+}
-- 
Anthony PERARD