On 04.09.20 18:56, Alexander Duyck wrote:
> On Fri, Sep 4, 2020 at 8:20 AM Jan Kiszka <> wrote:
>>
>> On 25.08.20 16:45, Alexander Duyck wrote:
>>> From: Alexander Duyck <>
>>>
>>> Free page hints allow the balloon driver to provide information on what
>>> pages are not currently in use so that we can avoid the cost of copying
>>> them in migration scenarios. Add a feature description for free page hints
>>> describing basic functioning and requirements.
>>>
>>> Acked-by: Cornelia Huck <>
>>> Reviewed-by: David Hildenbrand <>
>>> Signed-off-by: Alexander Duyck <>
>>> ---
>>> conformance.tex | 2 +
>>> content.tex | 161 +++++++++++++++++++++++++++++++++++++++++++++++++++++--
>>> 2 files changed, 157 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/conformance.tex b/conformance.tex
>>> index b6fdec090383..a14e26edfcb2 100644
>>> --- a/conformance.tex
>>> +++ b/conformance.tex
>>> @@ -149,6 +149,7 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets}
>>> \item \ref{drivernormative:Device Types / Memory Balloon Device / Feature bits}
>>> \item \ref{drivernormative:Device Types / Memory Balloon Device / Device Operation}
>>> \item \ref{drivernormative:Device Types / Memory Balloon Device / Device Operation / Memory Statistics}
>>> +\item \ref{drivernormative:Device Types / Memory Balloon Device / Device Operation / Free Page Hinting}
>>> \end{itemize}
>>>
>>> \conformance{\subsection}{SCSI Host Driver Conformance}\label{sec:Conformance / Driver Conformance / SCSI Host Driver Conformance}
>>> @@ -331,6 +332,7 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets}
>>> \item \ref{devicenormative:Device Types / Memory Balloon Device / Feature bits}
>>> \item \ref{devicenormative:Device Types / Memory Balloon Device / Device Operation}
>>> \item \ref{devicenormative:Device Types / Memory Balloon Device / Device Operation / Memory Statistics}
>>> +\item \ref{devicenormative:Device Types / Memory Balloon Device / Device Operation / Free Page Hinting}
>>> \end{itemize}
>>>
>>> \conformance{\subsection}{SCSI Host Device Conformance}\label{sec:Conformance / Device Conformance / SCSI Host Device Conformance}
>>> diff --git a/content.tex b/content.tex
>>> index 91735e3eb018..76dfce919b97 100644
>>> --- a/content.tex
>>> +++ b/content.tex
>>> @@ -5005,10 +5005,13 @@ \subsection{Virtqueues}\label{sec:Device Types / Memory Balloon Device / Virtque
>>> \begin{description}
>>> \item[0] inflateq
>>> \item[1] deflateq
>>> -\item[2] statsq.
>>> +\item[2] statsq
>>> +\item[3] free_page_vq
>>> \end{description}
>>>
>>> - Virtqueue 2 only exists if VIRTIO_BALLOON_F_STATS_VQ set.
>>> + statsq only exists if VIRTIO_BALLOON_F_STATS_VQ is set.
>>> +
>>> + free_page_vq only exists if VIRTIO_BALLOON_F_FREE_PAGE_HINT is set.
>>>
>>> \subsection{Feature bits}\label{sec:Device Types / Memory Balloon Device / Feature bits}
>>> \begin{description}
>>> @@ -5019,6 +5022,10 @@ \subsection{Feature bits}\label{sec:Device Types / Memory Balloon Device / Featu
>>> memory statistics is present.
>>> \item[VIRTIO_BALLOON_F_DEFLATE_ON_OOM (2) ] Deflate balloon on
>>> guest out of memory condition.
>>> +\item[ VIRTIO_BALLOON_F_FREE_PAGE_HINT(3) ] The device has support for free
>>> + page hinting. A virtqueue for providing hints as to what memory is
>>> + currently free is present. Configuration field \field{free_page_hint_cmd_id}
>>> + is valid.
>>>
>>> \end{description}
>>>
>>> @@ -5042,13 +5049,17 @@ \subsection{Feature bits}\label{sec:Device Types / Memory Balloon Device / Featu
>>> VIRTIO_BALLOON_F_MUST_TELL_HOST is not negotiated.
>>>
>>> \subsection{Device configuration layout}\label{sec:Device Types / Memory Balloon Device / Device configuration layout}
>>> - Both fields of this configuration
>>> - are always available.
>>> + \field{num_pages} and \field{actual} are always available.
>>> +
>>> + \field{free_page_hint_cmd_id} is available if
>>> + VIRTIO_BALLOON_F_FREE_PAGE_HINT has been negotiated and is read-only by
>>> + the driver.
>>
>> This reads at least to me like "...if VIRTIO_BALLOON_F_FREE_PAGE_HINT
>> ... is read-only by the driver". I suspect you rather meant
>> "free_page_hint_cmd_id is read-only...". Maybe split up into two sentences?
>
> Yes, the intention is:
> 1. free_page_hint_cmd_id is only available if
> VIRTIO_BALLOON_F_FREE_PAGE_HINT has been negotiated
> 2. free_page_hint_cmd_id is read only by the driver
>
> If needed I suppose we could break it up by splitting it into two
> sentences, or adding "the field" after the "and".
>
I'm fine with both options but please adjust this - on top (Michael just
opened the voting for this version again due to the formal typo in round 1).
Jan
--
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux
