Re: [Xen-devel] [PATCH 3/3] libxl: update vcpus bitmap in retrieved guest config

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

On Tue, Jun 07, 2016 at 12:24:02PM +0100, Wei Liu wrote:
> ... because the available vcpu bitmap can change during domain life time
> due to cpu hotplug and unplug.
> 
> For QEMU upstream, we interrogate QEMU for the number of vcpus. For
> others, we look directly into xenstore for information.
> 
> Reported-by: Jan Beulich <jbeulich@xxxxxxxx>
> Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> ---
>  tools/libxl/libxl.c | 91 
> +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 91 insertions(+)
> 
> diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
> index 006b83f..4f8b663 100644
> --- a/tools/libxl/libxl.c
> +++ b/tools/libxl/libxl.c
> @@ -7222,6 +7222,57 @@ void libxl_mac_copy(libxl_ctx *ctx, libxl_mac *dst, 
> libxl_mac *src)
>          (*dst)[i] = (*src)[i];
>  }
>  
> +static int libxl__update_avail_vcpus_qmp(libxl__gc *gc, uint32_t domid,
> +                                         unsigned int max_vcpus,
> +                                         libxl_bitmap *map)
> +{
> +    unsigned int count, i;
> +    int rc;
> +
> +    /* For QEMU upstream we always need to return the number
> +     * of cpus present to QEMU whether they are online or not;
> +     * otherwise QEMU won't accept the saved state.
> +     */
> +    rc = libxl__qmp_query_cpus(gc, domid, &count);
> +    if (rc) {
> +        LOG(ERROR, "fail to get number of cpus for domain %d", domid);
> +        goto out;
> +    }
> +
> +    for (i = 0; i < count; i++)
> +        libxl_bitmap_set(map, i);

What if I have cpu 1, 7 and 42 online, but all the other offline?

-- 
Anthony PERARD

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