Re: [Xen-devel] [PATCHv1] xen-blkback: default to X86_32 ABI on x86

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Thu, Feb 05, 2015 at 05:09:56PM +0000, David Vrabel wrote:
> Prior to the existance of 64-bit backends using the X86_64 ABI,
> frontends used the X86_32 ABI.  These old frontends do not specify the
> ABI and when used with a 64-bit backend do not work.

Whoa. How old are we talking? I had been using RHEL5 guests and
those work OK (64bit dom0, 32-bit domU).
> 
> On x86, default to the X86_32 ABI if one is not specified.  Backends
> on ARM continue to default to their NATIVE ABI.
> 
> Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
> ---
>  drivers/block/xen-blkback/common.h |    9 +++++++++
>  drivers/block/xen-blkback/xenbus.c |    4 ++--
>  2 files changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/block/xen-blkback/common.h 
> b/drivers/block/xen-blkback/common.h
> index f65b807..78b0411 100644
> --- a/drivers/block/xen-blkback/common.h
> +++ b/drivers/block/xen-blkback/common.h
> @@ -214,6 +214,15 @@ enum blkif_protocol {
>       BLKIF_PROTOCOL_X86_64 = 3,
>  };
>  
> +/*
> + * Default protocol if the frontend doesn't specify one.
> + */
> +#ifdef CONFIG_X86
> +#  define BLKIF_PROTOCOL_DEFAULT BLKIF_PROTOCOL_X86_32
> +#else
> +#  define BLKIF_PROTOCOL_DEFAULT BLKIF_PROTOCOL_NATIVE
> +#endif
> +
>  struct xen_vbd {
>       /* What the domain refers to this vbd as. */
>       blkif_vdev_t            handle;
> diff --git a/drivers/block/xen-blkback/xenbus.c 
> b/drivers/block/xen-blkback/xenbus.c
> index 630a489..e3afe97 100644
> --- a/drivers/block/xen-blkback/xenbus.c
> +++ b/drivers/block/xen-blkback/xenbus.c
> @@ -868,11 +868,11 @@ static int connect_ring(struct backend_info *be)
>               return err;
>       }
>  
> -     be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
> +     be->blkif->blk_protocol = BLKIF_PROTOCOL_DEFAULT;
>       err = xenbus_gather(XBT_NIL, dev->otherend, "protocol",
>                           "%63s", protocol, NULL);
>       if (err)
> -             strcpy(protocol, "unspecified, assuming native");
> +             strcpy(protocol, "unspecified, assuming default");
>       else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE))
>               be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
>       else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32))
> -- 
> 1.7.10.4
> 

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