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Subject: Re: [virtio-comment] [PATCH v4 1/3] content: Document balloon feature page poison
On 29.05.20 18:57, Alexander Duyck wrote: > On Fri, May 29, 2020 at 1:13 AM David Hildenbrand <david@redhat.com> wrote: >> >> On 27.05.20 06:06, Alexander Duyck wrote: >>> From: Alexander Duyck <alexander.h.duyck@linux.intel.com> >>> >>> Page poison provides a way for the guest to notify the host that it is >>> initializing or poisoning freed pages with some specific poison value. As a >>> result of this we can infer a couple traits about the guest: >>> >>> 1. Free pages will contain a specific pattern within the guest. >>> 2. Modifying free pages from this value may cause an error in the guest. >>> 3. Pages will be immediately written to by the driver when deflated. >>> >>> There are currently no existing features that make use of this data. In the >>> upcoming feature free page reporting we will need to make use of this to >>> identify if we can evict pages from the guest without causing data >>> corruption. >>> >>> Add documentation for the page poison feature describing the basic >>> functionality and requirements. >>> >>> Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com> >>> --- >>> conformance.tex | 2 ++ >>> content.tex | 59 +++++++++++++++++++++++++++++++++++++++++++++++++++---- >>> 2 files changed, 57 insertions(+), 4 deletions(-) >>> >>> diff --git a/conformance.tex b/conformance.tex >>> index b6fdec090383..4ed9d62e8088 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 / Page Poison} >>> \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 / Page Poison} >>> \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..4a0ab90260ff 100644 >>> --- a/content.tex >>> +++ b/content.tex >>> @@ -5019,6 +5019,9 @@ \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_PAGE_POISON(4) ] A hint to the device, that the driver >>> + will immediately write \field{poison_val} to pages after deflating them. >>> + Configuration field \field{poison_val} is valid. >>> >> >> Here we have "that the driver will immediately" ... >> >> But we never document that in form of a normative statement (e.g., "The >> driver MUST initialize pages with \field{poison_val} after deflating"). > > I'm pretty sure we did document that. In the normative statement for > the driver below we have: > +The driver MUST initialize the deflated pages with \field{poison_val} when > +they are reused by the driver. > Doh! I think I missed that somehow Reviewed-by: David Hildenbrand <david@redhat.com> Thanks! -- Thanks, David / dhildenb
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