[virtio-dev] [PATCH] content: reserve device ID for virtio-pmem devices

[virtio-dev] [PATCH] content: reserve device ID for virtio-pmem devices

[Pankaj Gupta]

We need a device ID for virtio-pmem devices. As 24 is already 
requested by virtio-mem, so requesting next available(25)

Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
---
 content.tex | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/content.tex b/content.tex
index 7a92cb1..ef75dc5 100644
--- a/content.tex
+++ b/content.tex
@@ -2432,6 +2432,8 @@ Device ID  &  Virtio Device    \\
 \hline
 23         &   IOMMU device \\
 \hline
+25         &   PMEM device \\
+\hline
 \end{tabular}
 
 Some of the devices above are unspecified by this document,
-- 
2.14.3


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Re: [virtio-dev] [PATCH] content: reserve device ID for virtio-pmem devices

[Stefan Hajnoczi]

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On Fri, May 18, 2018 at 10:11:06AM +0530, Pankaj Gupta wrote:
> We need a device ID for virtio-pmem devices. As 24 is already 
> requested by virtio-mem, so requesting next available(25)
> 
> Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
> ---
>  content.tex | 2 ++
>  1 file changed, 2 insertions(+)

virtio-mem is designed for hotplug.  Does it make sense to merge
virtio-pmem into virtio-mem since you'll need hotplug too?

Stefan

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Re: [virtio-dev] [PATCH] content: reserve device ID for virtio-pmem devices

[David Hildenbrand]

On 22.05.2018 11:42, Stefan Hajnoczi wrote:
> On Fri, May 18, 2018 at 10:11:06AM +0530, Pankaj Gupta wrote:
>> We need a device ID for virtio-pmem devices. As 24 is already 
>> requested by virtio-mem, so requesting next available(25)
>>
>> Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
>> ---
>>  content.tex | 2 ++
>>  1 file changed, 2 insertions(+)
> 
> virtio-mem is designed for hotplug.  Does it make sense to merge
> virtio-pmem into virtio-mem since you'll need hotplug too?
> 
> Stefan
> 
Hi Stefan,

Initially I had (and even proposed during some discussion) the same
idea. But it turns out that they are fundamentally different.

They are memory devices, yes, but that's the point where they stop being
similar.

While virtio-pmem wants to expose a memory region as persistent memory
and adding a flushing interface, virtio-mem is all about managing
(add/remove/online/offline) sub-chunks and applying protection
mechanisms on the hypervisor side to make sure unplugged memory cannot
(or only in some limited sense) be accessed.

-- 

Thanks,

David / dhildenb

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Re: [virtio-dev] [PATCH] content: reserve device ID for virtio-pmem devices

[Pankaj Gupta]

Hi Stefan,

> >> We need a device ID for virtio-pmem devices. As 24 is already
> >> requested by virtio-mem, so requesting next available(25)
> >>
> >> Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
> >> ---
> >>  content.tex | 2 ++
> >>  1 file changed, 2 insertions(+)
> > 
> > virtio-mem is designed for hotplug.  Does it make sense to merge
> > virtio-pmem into virtio-mem since you'll need hotplug too?
> > 
> > Stefan
> > 
> Hi Stefan,
> 
> Initially I had (and even proposed during some discussion) the same
> idea. But it turns out that they are fundamentally different.
> 
> They are memory devices, yes, but that's the point where they stop being
> similar.
> 
> While virtio-pmem wants to expose a memory region as persistent memory
> and adding a flushing interface, virtio-mem is all about managing
> (add/remove/online/offline) sub-chunks and applying protection
> mechanisms on the hypervisor side to make sure unplugged memory cannot
> (or only in some limited sense) be accessed.

Yes, we discussed possibility of merging both these devices in the past.
As rightly explained by David, both these devices solving different problems.
Also, their architectures are different, common part is both use memory device 
& VIRTIO.

Also, as we plan to add more features specific to each virtio{mem/pmem}, it 
will be more confusing and difficult to maintain. I think it makes more sense to 
keep both these devices separate. 

Thanks,
Pankaj


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Re: [virtio-dev] [PATCH] content: reserve device ID for virtio-pmem devices

[Stefan Hajnoczi]

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On Wed, May 23, 2018 at 01:01:20AM -0400, Pankaj Gupta wrote:
> 
> Hi Stefan,
> 
> > >> We need a device ID for virtio-pmem devices. As 24 is already
> > >> requested by virtio-mem, so requesting next available(25)
> > >>
> > >> Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
> > >> ---
> > >>  content.tex | 2 ++
> > >>  1 file changed, 2 insertions(+)
> > > 
> > > virtio-mem is designed for hotplug.  Does it make sense to merge
> > > virtio-pmem into virtio-mem since you'll need hotplug too?
> > > 
> > > Stefan
> > > 
> > Hi Stefan,
> > 
> > Initially I had (and even proposed during some discussion) the same
> > idea. But it turns out that they are fundamentally different.
> > 
> > They are memory devices, yes, but that's the point where they stop being
> > similar.
> > 
> > While virtio-pmem wants to expose a memory region as persistent memory
> > and adding a flushing interface, virtio-mem is all about managing
> > (add/remove/online/offline) sub-chunks and applying protection
> > mechanisms on the hypervisor side to make sure unplugged memory cannot
> > (or only in some limited sense) be accessed.
> 
> Yes, we discussed possibility of merging both these devices in the past.
> As rightly explained by David, both these devices solving different problems.
> Also, their architectures are different, common part is both use memory device 
> & VIRTIO.
> 
> Also, as we plan to add more features specific to each virtio{mem/pmem}, it 
> will be more confusing and difficult to maintain. I think it makes more sense to 
> keep both these devices separate. 

Okay.

Stefan

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Re: [virtio-dev] [PATCH] content: reserve device ID for virtio-pmem devices

[Pankaj Gupta]

ping. 

I have also opened a github issue[1] for the same.

[1] https://github.com/oasis-tcs/virtio-spec/issues/38

Thanks,
Pankaj

> 
> We need a device ID for virtio-pmem devices. As 24 is already
> requested by virtio-mem, so requesting next available(25)
> 
> Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
> ---
>  content.tex | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/content.tex b/content.tex
> index 7a92cb1..ef75dc5 100644
> --- a/content.tex
> +++ b/content.tex
> @@ -2432,6 +2432,8 @@ Device ID  &  Virtio Device    \\
>  \hline
>  23         &   IOMMU device \\
>  \hline
> +25         &   PMEM device \\
> +\hline
>  \end{tabular}
>  
>  Some of the devices above are unspecified by this document,
> --
> 2.14.3
> 
> 
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> 
> 

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[virtio-dev] [PATCH] content: reserve device ID for virtio-pmem devices

[Pankaj Gupta]

We need a device ID for virtio-pmem devices. As 25 is  
requested by audio device, so requesting next available(26).
Also, updated the previously requested github issue[1] for
voting.

[1] https://github.com/oasis-tcs/virtio-spec/issues/38

Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
---
 content.tex | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/content.tex b/content.tex
index 193b6e1..aef7476 100644
--- a/content.tex
+++ b/content.tex
@@ -2634,6 +2634,8 @@ \chapter{Device Types}\label{sec:Device Types}
 \hline
 24         &   Memory device \\
 \hline
+26         &   PMEM device \\
+\hline
 \end{tabular}
 
 Some of the devices above are unspecified by this document,
-- 
2.14.5


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