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Subject: Re: [virtio-dev] [PATCH v8 1/3] content: Document balloon feature free page hints
On Fri, Sep 4, 2020 at 8:20 AM Jan Kiszka <jan.kiszka@siemens.com> wrote: > > On 25.08.20 16:45, Alexander Duyck wrote: > > From: Alexander Duyck <alexander.h.duyck@linux.intel.com> > > > > 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 <cohuck@redhat.com> > > Reviewed-by: David Hildenbrand <david@redhat.com> > > Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com> > > --- > > 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". Thanks. - Alex
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