linux-kernel - Re: [RFC][Patch v10 2/2] virtio-balloon: page

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Date:   Tue, 4 Jun 2019 09:33:28 -0700
From:   Alexander Duyck <alexander.duyck@...il.com>
To:     Nitesh Narayan Lal <nitesh@...hat.com>
Cc:     kvm list <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>,
        Paolo Bonzini <pbonzini@...hat.com>, lcapitulino@...hat.com,
        pagupta@...hat.com, wei.w.wang@...el.com,
        Yang Zhang <yang.zhang.wz@...il.com>,
        Rik van Riel <riel@...riel.com>,
        David Hildenbrand <david@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>, dodgen@...gle.com,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        dhildenb@...hat.com, Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [RFC][Patch v10 2/2] virtio-balloon: page_hinting: reporting to
 the host

On Mon, Jun 3, 2019 at 10:04 AM Nitesh Narayan Lal <nitesh@...hat.com> wrote:
>
> Enables the kernel to negotiate VIRTIO_BALLOON_F_HINTING feature with the
> host. If it is available and page_hinting_flag is set to true, page_hinting
> is enabled and its callbacks are configured along with the max_pages count
> which indicates the maximum number of pages that can be isolated and hinted
> at a time. Currently, only free pages of order >= (MAX_ORDER - 2) are
> reported. To prevent any false OOM max_pages count is set to 16.
>
> By default page_hinting feature is enabled and gets loaded as soon
> as the virtio-balloon driver is loaded. However, it could be disabled
> by writing the page_hinting_flag which is a virtio-balloon parameter.
>
> Signed-off-by: Nitesh Narayan Lal <nitesh@...hat.com>
> ---
>  drivers/virtio/virtio_balloon.c     | 112 +++++++++++++++++++++++++++-
>  include/uapi/linux/virtio_balloon.h |  14 ++++
>  2 files changed, 125 insertions(+), 1 deletion(-)

<snip>

> diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h
> index a1966cd7b677..25e4f817c660 100644
> --- a/include/uapi/linux/virtio_balloon.h
> +++ b/include/uapi/linux/virtio_balloon.h
> @@ -29,6 +29,7 @@
>  #include <linux/virtio_types.h>
>  #include <linux/virtio_ids.h>
>  #include <linux/virtio_config.h>
> +#include <linux/page_hinting.h>

So this include breaks the build and from what I can tell it isn't
really needed. I deleted it in order to be able to build without
warnings about the file not being included in UAPI.

>  /* The feature bitmap for virtio balloon */
>  #define VIRTIO_BALLOON_F_MUST_TELL_HOST        0 /* Tell before reclaiming pages */
> @@ -36,6 +37,7 @@
>  #define VIRTIO_BALLOON_F_DEFLATE_ON_OOM        2 /* Deflate balloon on OOM */
>  #define VIRTIO_BALLOON_F_FREE_PAGE_HINT        3 /* VQ to report free pages */
>  #define VIRTIO_BALLOON_F_PAGE_POISON   4 /* Guest is using page poisoning */
> +#define VIRTIO_BALLOON_F_HINTING       5 /* Page hinting virtqueue */
>
>  /* Size of a PFN in the balloon interface. */
>  #define VIRTIO_BALLOON_PFN_SHIFT 12
> @@ -108,4 +110,16 @@ struct virtio_balloon_stat {
>         __virtio64 val;
>  } __attribute__((packed));
>
> +#ifdef CONFIG_PAGE_HINTING
> +/*
> + * struct hinting_data- holds the information associated with hinting.
> + * @phys_add:  physical address associated with a page or the array holding
> + *             the array of isolated pages.
> + * @size:      total size associated with the phys_addr.
> + */
> +struct hinting_data {
> +       __virtio64 phys_addr;
> +       __virtio32 size;
> +};
> +#endif
>  #endif /* _LINUX_VIRTIO_BALLOON_H */
> --
> 2.21.0
>