Re: [PATCH v2 1/2] xen/balloon: Notify a host about a guest memorysize limit

From: Ian Campbell
Date: Mon Apr 29 2013 - 10:35:22 EST


On Mon, 2013-04-29 at 12:37 +0100, Daniel Kiper wrote:
> Notify a host about a guest memory size limit.
>
> Idea of this patch was discussed with Ian Campbell and Ian Jackson.
>
> Signed-off-by: Daniel Kiper <daniel.kiper@xxxxxxxxxx>
> ---
> drivers/xen/balloon.c | 25 +++++++++++++++++++++++++
> 1 file changed, 25 insertions(+)
>
> diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
> index a56776d..856661f 100644
> --- a/drivers/xen/balloon.c
> +++ b/drivers/xen/balloon.c
> @@ -65,6 +65,7 @@
> #include <xen/balloon.h>
> #include <xen/features.h>
> #include <xen/page.h>
> +#include <xen/xenbus.h>
>
> /*
> * balloon_process() state:
> @@ -586,6 +587,9 @@ static void __init balloon_add_region(unsigned long start_pfn,
> static int __init balloon_init(void)
> {
> int i;
> +#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
> + int rc;
> +#endif
>
> if (!xen_domain())
> return -ENODEV;
> @@ -621,6 +625,27 @@ static int __init balloon_init(void)
> balloon_add_region(PFN_UP(xen_extra_mem[i].start),
> PFN_DOWN(xen_extra_mem[i].size));
>
> +#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
> + /*
> + * Notify a host about our memory size limit.
> + *
> + * The guest-max value is in KiB, so MAX_DOMAIN_PAGES should
> + * be converted respectively. PAGE_SHIFT converts pages to bytes,
> + * hence PAGE_SHIFT - 10.
> + */
> + rc = xenbus_printf(XBT_NIL, "memory", "guest-max", "%lu",
> + MAX_DOMAIN_PAGES << (PAGE_SHIFT - 10));
> +
> + if (rc < 0)
> + pr_info("xen/balloon: Memory hotplug may not be supported "
> + "in some environments: %i\n", rc);
> +#else
> + xenbus_printf(XBT_NIL, "memory", "guest-max", "%lu",

Would it be OK to not do anything in the non-hotplug case? That's just
the historical behaviour right?

Would you expect this value to differ from static-max?

> + (balloon_stats.current_pages +
> + balloon_stats.balloon_low +
> + balloon_stats.balloon_high) << (PAGE_SHIFT - 10));
> +#endif
> +
> return 0;
> }
>


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/