Re: [Xen-devel] Re: [patch/rfc] multiprotocol blkback drivers (32-on-64)

["Jan Beulich" <jbeulich@xxxxxxxxxx>]

By adding abstraction to the ring macros and the affected headers, and then 
replacing
direct structure member accesses with appropriate macros. Reference patches
attached (not checked whether they would apply cleanly on -unstable). Jan

>>> Keir Fraser <keir@xxxxxxxxxxxxx> 18.12.06 18:58 >>>
Gerd's description is along the lines of what I would implement myself. How
does your bi-modal approach work?

 -- Keir

On 18/12/06 17:09, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote:

> I understand you favor this over the bi-modal approach I took? Any specific
> advantages? Jan
> 
>>>> Gerd Hoffmann <kraxel@xxxxxxx> 18.12.06 17:39 >>>
> Hi,
> 
> This is a patch for the block interface, frontend drivers, backend
> drivers and tools to support multiple ring protocols.  Right there are
> now just two: the 32bit and the 64bit one.  If needed it can be extended.
> 
> Interface changes (io/blkif.h)
>  * Have both request structs there, with "v1" and "v2" added to the
>    name.  The old name is aliased to the native protocol of the
>    architecture.
>  * Add helper functions to convert v1/v2 requests to native.
> 
> Frontend changes:
>  * Create a new node "protocol", add the protocol number it speaks
>    there.
> 
> Backend changes:
>  * Look at the "protocol" number of the frontend and switch ring
>    handling accordingly.  If the protocol node isn't present it assumes
>    native protocol.
>  * As the request struct is copied anyway before being processed (for
>    security reasons) it is converted to native at that point so most
>    backend code doesn't need to know what the frontend speaks.
>  * In case of blktap this is completely transparent to userspace, the
>    kernel/userspace ring is always native no matter what the frontend
>    speaks.
> 
> Tools changes:
>  * Add one more option to the disk configuration, so one can specify the
>    protocol the frontend speaks in the config file.  This is needed for
>    old frontends which don't advertise the protocol they are speaking
>    themself.
>    I'm not that happy with this approach, but it works for now and I'm
>    kida lost in the stack of python classes doing domain and device
>    handling ...
> 
> Consider the code experimental, not all frontend/backend combinations
> are tested.
> 
> Comments?  Questions?  Suggesions?
> 
> cheers,
>   Gerd
> 
> PS: Anyone working on blkback/blktap code sharing?  While walking
>     through the code I've noticed quite alot of it is cut&paste ...


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Attachment: xen-bimodal-tpmback.patch
Description: Text document

Attachment: xen-bimodal-blkif.patch
Description: Text document

Attachment: xen-bimodal-blktap.patch
Description: Text document

Attachment: xen-bimodal-blkback.patch
Description: Text document

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