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

[Stefano Stabellini <stefano.stabellini@eu.citrix.com>]

On Fri, 31 May 2013, Anthony PERARD wrote:
> 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;
>      }

I see where this change is coming from now but..

> @@ -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);
>  }

..the pm_update_sci is still in place


> 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
>