Re: [RFC][Patch v10 2/2] virtio-balloon: page_hinting: reporting to the host

[Nitesh Narayan Lal]

On 6/4/19 12:33 PM, Alexander Duyck wrote:
> On Mon, Jun 3, 2019 at 10:04 AM Nitesh Narayan Lal <nitesh@xxxxxxxxxx> 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@xxxxxxxxxx>
>> ---
>>  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.
I agree here, it is not required any more.
>
>>  /* 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
>>
-- 
Regards
Nitesh

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