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Re: [PATCH 1/3] virtio: Basic implementation of virtio pstore driver

From "Michael S. Tsirkin" <mst@redhat.com>
Newsgroups linux.kernel
Subject Re: [PATCH 1/3] virtio: Basic implementation of virtio pstore driver
Date 2016-11-15 15:40 +0100
Message-ID <sDN3X-69H-1@gated-at.bofh.it> (permalink)
References (1 earlier) <s89Fv-tR-5@gated-at.bofh.it> <sC0I2-h7-33@gated-at.bofh.it> <sDE0G-cO-21@gated-at.bofh.it> <sDEal-vS-3@gated-at.bofh.it> <sDEWJ-Oi-1@gated-at.bofh.it>
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On Tue, Nov 15, 2016 at 02:50:11PM +0900, Namhyung Kim wrote:
> On Tue, Nov 15, 2016 at 07:06:28AM +0200, Michael S. Tsirkin wrote:
> > On Tue, Nov 15, 2016 at 01:50:21PM +0900, Namhyung Kim wrote:
> > > On Thu, Nov 10, 2016 at 06:39:55PM +0200, Michael S. Tsirkin wrote:
> > > [SNIP]
> > > > > +struct virtio_pstore_fileinfo {
> > > > > +	__virtio64		id;
> > > > > +	__virtio32		count;
> > > > > +	__virtio16		type;
> > > > > +	__virtio16		unused;
> > > > > +	__virtio32		flags;
> > > > > +	__virtio32		len;
> > > > > +	__virtio64		time_sec;
> > > > > +	__virtio32		time_nsec;
> > > > > +	__virtio32		reserved;
> > > > > +};
> > > > > +
> > > > > +struct virtio_pstore_config {
> > > > > +	__virtio32		bufsize;
> > > > > +};
> > > > > +
> > > > 
> > > > What exactly does each field mean? I'm especially
> > > > interested in time fields - maintaining a consistent
> > > > time between host and guest is not a simple problem.
> > > 
> > > These are required by pstore and will be used to create corresponding
> > > files in the pstore filesystem.  The time fields are for mtime and
> > > ctime and, I think, it's just a hint for user and doesn't require
> > > strict consistency.
> > 
> > Pls add documentation. I would just drop hints for now.
> 
> Well, I'll add docmentation.  But I think just dropping might not good
> since they all have host time and it's helpful to know their relative
> difference in guest.
> 
> Thanks,
> Namhyung

If it's part of host/guest ABI it needs to be better defined.
"It's just a hint does not need to be exact" is too vague,
we need to specify what kind of change will or will not
break guests.

-- 
MST

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Thread

Re: [PATCH 1/3] virtio: Basic implementation of virtio pstore driver Namhyung Kim <namhyung@kernel.org> - 2016-11-15 06:00 +0100
  Re: [PATCH 1/3] virtio: Basic implementation of virtio pstore driver "Michael S. Tsirkin" <mst@redhat.com> - 2016-11-15 06:10 +0100
    Re: [PATCH 1/3] virtio: Basic implementation of virtio pstore driver Namhyung Kim <namhyung@kernel.org> - 2016-11-15 07:00 +0100
      Re: [PATCH 1/3] virtio: Basic implementation of virtio pstore driver "Michael S. Tsirkin" <mst@redhat.com> - 2016-11-15 15:40 +0100
    Re: [PATCH 1/3] virtio: Basic implementation of virtio pstore driver Paolo Bonzini <pbonzini@redhat.com> - 2016-11-15 11:00 +0100
      Re: [PATCH 1/3] virtio: Basic implementation of virtio pstore driver Namhyung Kim <namhyung@kernel.org> - 2016-11-15 15:40 +0100
        Re: [PATCH 1/3] virtio: Basic implementation of virtio pstore driver Paolo Bonzini <pbonzini@redhat.com> - 2016-11-15 15:40 +0100
          Re: [PATCH 1/3] virtio: Basic implementation of virtio pstore driver Namhyung Kim <namhyung@kernel.org> - 2016-11-16 08:10 +0100
            Re: [PATCH 1/3] virtio: Basic implementation of virtio pstore  driver Paolo Bonzini <pbonzini@redhat.com> - 2016-11-16 13:20 +0100
              Re: [PATCH 1/3] virtio: Basic implementation of virtio pstore driver Namhyung Kim <namhyung@kernel.org> - 2016-11-18 04:40 +0100
                Re: [PATCH 1/3] virtio: Basic implementation of virtio pstore driver "Michael S. Tsirkin" <mst@redhat.com> - 2016-11-18 05:10 +0100
                Re: [virtio-dev] Re: [PATCH 1/3] virtio: Basic implementation of  virtio pstore driver Paolo Bonzini <pbonzini@redhat.com> - 2016-11-18 10:50 +0100
                Re: [PATCH 1/3] virtio: Basic implementation of virtio pstore driver Paolo Bonzini <pbonzini@redhat.com> - 2016-11-18 10:50 +0100

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