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

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

[David Vrabel]

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.

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@citrix.com>
---
 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

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

[Konrad Rzeszutek Wilk]

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@citrix.com>
> ---
>  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
> 

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

[David Vrabel]

On 05/02/15 19:44, Konrad Rzeszutek Wilk wrote:
> 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).

Unfortunately I can't remember and the internal commit is tagged with
the wrong bug number.  I think it was either sles 9 or rhel 4.

David

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

[Roger Pau Monné]

El 05/02/15 a les 18.09, David Vrabel ha escrit:
> 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.
> 
> 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@citrix.com>

I don't see anything wrong with changing the default protocol from
native to the 32bit variant.

Acked-by: Roger Pau Monné <roger.pau@citrix.com>

Roger.