[PATCH] xen: fix qdisk BLKIF_OP_DISCARD for 32/64 word size mix

[PATCH] xen: fix qdisk BLKIF_OP_DISCARD for 32/64 word size mix

[Juergen Gross]

In case the word size of the domU and qemu running the qdisk backend
differ BLKIF_OP_DISCARD will not work reliably, as the request
structure in the ring have different layouts for different word size.

Correct this by copying the request structure in case of different
word size element by element in the BLKIF_OP_DISCARD case, too.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 hw/block/xen_blkif.h | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/hw/block/xen_blkif.h b/hw/block/xen_blkif.h
index e3b133b..969112f 100644
--- a/hw/block/xen_blkif.h
+++ b/hw/block/xen_blkif.h
@@ -26,6 +26,14 @@ struct blkif_x86_32_request {
 	blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
 	struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 };
+struct blkif_x86_32_request_discard {
+    uint8_t        operation;    /* BLKIF_OP_DISCARD                     */
+    uint8_t        flag;         /* nr_segments in request struct        */
+    blkif_vdev_t   handle;       /* only for read/write requests         */
+    uint64_t       id;           /* private guest value, echoed in resp  */
+    blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
+    uint64_t       nr_sectors;   /* # of contiguous sectors to discard   */
+};
 struct blkif_x86_32_response {
 	uint64_t        id;              /* copied from request */
 	uint8_t         operation;       /* copied from request */
@@ -44,6 +52,14 @@ struct blkif_x86_64_request {
 	blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
 	struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 };
+struct blkif_x86_64_request_discard {
+    uint8_t        operation;    /* BLKIF_OP_DISCARD                     */
+    uint8_t        flag;         /* nr_segments in request struct        */
+    blkif_vdev_t   handle;       /* only for read/write requests         */
+    uint64_t       __attribute__((__aligned__(8))) id;
+    blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
+    uint64_t       nr_sectors;   /* # of contiguous sectors to discard   */
+};
 struct blkif_x86_64_response {
 	uint64_t       __attribute__((__aligned__(8))) id;
 	uint8_t         operation;       /* copied from request */
@@ -82,7 +98,7 @@ static inline void blkif_get_x86_32_req(blkif_request_t *dst, blkif_x86_32_reque
 	/* Prevent the compiler from using src->... instead. */
 	barrier();
 	if (dst->operation == BLKIF_OP_DISCARD) {
-		struct blkif_request_discard *s = (void *)src;
+                struct blkif_x86_32_request_discard *s = (void *)src;
 		struct blkif_request_discard *d = (void *)dst;
 		d->nr_sectors = s->nr_sectors;
 		return;
@@ -105,7 +121,7 @@ static inline void blkif_get_x86_64_req(blkif_request_t *dst, blkif_x86_64_reque
 	/* Prevent the compiler from using src->... instead. */
 	barrier();
 	if (dst->operation == BLKIF_OP_DISCARD) {
-		struct blkif_request_discard *s = (void *)src;
+                struct blkif_x86_64_request_discard *s = (void *)src;
 		struct blkif_request_discard *d = (void *)dst;
 		d->nr_sectors = s->nr_sectors;
 		return;
-- 
2.6.6


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Re: [PATCH] xen: fix qdisk BLKIF_OP_DISCARD for 32/64 word size mix

[Jan Beulich]

>>> On 16.06.16 at 12:02, <JGross@suse.com> wrote:
> In case the word size of the domU and qemu running the qdisk backend
> differ BLKIF_OP_DISCARD will not work reliably, as the request
> structure in the ring have different layouts for different word size.
> 
> Correct this by copying the request structure in case of different
> word size element by element in the BLKIF_OP_DISCARD case, too.
> 
> Signed-off-by: Juergen Gross <jgross@suse.com>

With the indentation (tabs vs blanks) fixed
Reviewed-by: Jan Beulich <jbeulich@suse.com>

And maybe ...

> @@ -82,7 +98,7 @@ static inline void blkif_get_x86_32_req(blkif_request_t *dst, blkif_x86_32_reque
>  	/* Prevent the compiler from using src->... instead. */
>  	barrier();
>  	if (dst->operation == BLKIF_OP_DISCARD) {
> -		struct blkif_request_discard *s = (void *)src;
> +                struct blkif_x86_32_request_discard *s = (void *)src;

... it would also be worth adding const here and ...

> @@ -105,7 +121,7 @@ static inline void blkif_get_x86_64_req(blkif_request_t *dst, blkif_x86_64_reque
>  	/* Prevent the compiler from using src->... instead. */
>  	barrier();
>  	if (dst->operation == BLKIF_OP_DISCARD) {
> -		struct blkif_request_discard *s = (void *)src;
> +                struct blkif_x86_64_request_discard *s = (void *)src;

... here.

Jan


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Re: [PATCH] xen: fix qdisk BLKIF_OP_DISCARD for 32/64 word size mix

[Juergen Gross]

On 16/06/16 12:54, Jan Beulich wrote:
>>>> On 16.06.16 at 12:02, <JGross@suse.com> wrote:
>> In case the word size of the domU and qemu running the qdisk backend
>> differ BLKIF_OP_DISCARD will not work reliably, as the request
>> structure in the ring have different layouts for different word size.
>>
>> Correct this by copying the request structure in case of different
>> word size element by element in the BLKIF_OP_DISCARD case, too.
>>
>> Signed-off-by: Juergen Gross <jgross@suse.com>
> 
> With the indentation (tabs vs blanks) fixed

Hmm, qemu coding style is to use blanks. I could:
a) leave the patch as is (changed lines indented with blanks)
b) use tabs to indent (style of the modified file up to now)
c) change the style of the file in this patch
d) change the style of the file in a separate patch

Any preferences?

> Reviewed-by: Jan Beulich <jbeulich@suse.com>
> 
> And maybe ...
> 
>> @@ -82,7 +98,7 @@ static inline void blkif_get_x86_32_req(blkif_request_t *dst, blkif_x86_32_reque
>>  	/* Prevent the compiler from using src->... instead. */
>>  	barrier();
>>  	if (dst->operation == BLKIF_OP_DISCARD) {
>> -		struct blkif_request_discard *s = (void *)src;
>> +                struct blkif_x86_32_request_discard *s = (void *)src;
> 
> ... it would also be worth adding const here and ...
> 
>> @@ -105,7 +121,7 @@ static inline void blkif_get_x86_64_req(blkif_request_t *dst, blkif_x86_64_reque
>>  	/* Prevent the compiler from using src->... instead. */
>>  	barrier();
>>  	if (dst->operation == BLKIF_OP_DISCARD) {
>> -		struct blkif_request_discard *s = (void *)src;
>> +                struct blkif_x86_64_request_discard *s = (void *)src;
> 
> ... here.

Okay.


Juergen

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Re: [PATCH] xen: fix qdisk BLKIF_OP_DISCARD for 32/64 word size mix

[Jan Beulich]

>>> On 16.06.16 at 13:04, <JGross@suse.com> wrote:
> On 16/06/16 12:54, Jan Beulich wrote:
>>>>> On 16.06.16 at 12:02, <JGross@suse.com> wrote:
>>> In case the word size of the domU and qemu running the qdisk backend
>>> differ BLKIF_OP_DISCARD will not work reliably, as the request
>>> structure in the ring have different layouts for different word size.
>>>
>>> Correct this by copying the request structure in case of different
>>> word size element by element in the BLKIF_OP_DISCARD case, too.
>>>
>>> Signed-off-by: Juergen Gross <jgross@suse.com>
>> 
>> With the indentation (tabs vs blanks) fixed
> 
> Hmm, qemu coding style is to use blanks. I could:
> a) leave the patch as is (changed lines indented with blanks)
> b) use tabs to indent (style of the modified file up to now)
> c) change the style of the file in this patch
> d) change the style of the file in a separate patch
> 
> Any preferences?

I'd say a) is not an option, but beyond that I think this needs to be
answered by the qemu maintainers.

Jan


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Re: [Xen-devel] [PATCH] xen: fix qdisk BLKIF_OP_DISCARD for 32/64 word size mix

[Paul Durrant]

> -----Original Message-----
> From: Xen-devel [mailto:xen-devel-bounces@lists.xen.org] On Behalf Of
> Juergen Gross
> Sent: 16 June 2016 11:02
> To: qemu-devel@nongnu.org; xen-devel@lists.xensource.com
> Cc: Anthony Perard; Juergen Gross; sstabellini@kernel.org;
> kraxel@redhat.com
> Subject: [Xen-devel] [PATCH] xen: fix qdisk BLKIF_OP_DISCARD for 32/64
> word size mix
> 
> In case the word size of the domU and qemu running the qdisk backend
> differ BLKIF_OP_DISCARD will not work reliably, as the request
> structure in the ring have different layouts for different word size.
> 
> Correct this by copying the request structure in case of different
> word size element by element in the BLKIF_OP_DISCARD case, too.
> 
> Signed-off-by: Juergen Gross <jgross@suse.com>

Would it not be better to re-import the canonical blkif header as a whole rather than cherry-picking like this? You'd need to post-process to maintain style and possibly change some names for compatibility etc. but probably nothing beyond what indent and a simple [s]ed script can do.
I did broadly the same thing to re-import the netif header into Linux recently.

  Paul

> ---
>  hw/block/xen_blkif.h | 20 ++++++++++++++++++--
>  1 file changed, 18 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/block/xen_blkif.h b/hw/block/xen_blkif.h
> index e3b133b..969112f 100644
> --- a/hw/block/xen_blkif.h
> +++ b/hw/block/xen_blkif.h
> @@ -26,6 +26,14 @@ struct blkif_x86_32_request {
>  	blkif_sector_t sector_number;/* start sector idx on disk (r/w only)
> */
>  	struct blkif_request_segment
> seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
>  };
> +struct blkif_x86_32_request_discard {
> +    uint8_t        operation;    /* BLKIF_OP_DISCARD                     */
> +    uint8_t        flag;         /* nr_segments in request struct        */
> +    blkif_vdev_t   handle;       /* only for read/write requests         */
> +    uint64_t       id;           /* private guest value, echoed in resp  */
> +    blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
> +    uint64_t       nr_sectors;   /* # of contiguous sectors to discard   */
> +};
>  struct blkif_x86_32_response {
>  	uint64_t        id;              /* copied from request */
>  	uint8_t         operation;       /* copied from request */
> @@ -44,6 +52,14 @@ struct blkif_x86_64_request {
>  	blkif_sector_t sector_number;/* start sector idx on disk (r/w only)
> */
>  	struct blkif_request_segment
> seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
>  };
> +struct blkif_x86_64_request_discard {
> +    uint8_t        operation;    /* BLKIF_OP_DISCARD                     */
> +    uint8_t        flag;         /* nr_segments in request struct        */
> +    blkif_vdev_t   handle;       /* only for read/write requests         */
> +    uint64_t       __attribute__((__aligned__(8))) id;
> +    blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
> +    uint64_t       nr_sectors;   /* # of contiguous sectors to discard   */
> +};
>  struct blkif_x86_64_response {
>  	uint64_t       __attribute__((__aligned__(8))) id;
>  	uint8_t         operation;       /* copied from request */
> @@ -82,7 +98,7 @@ static inline void blkif_get_x86_32_req(blkif_request_t
> *dst, blkif_x86_32_reque
>  	/* Prevent the compiler from using src->... instead. */
>  	barrier();
>  	if (dst->operation == BLKIF_OP_DISCARD) {
> -		struct blkif_request_discard *s = (void *)src;
> +                struct blkif_x86_32_request_discard *s = (void *)src;
>  		struct blkif_request_discard *d = (void *)dst;
>  		d->nr_sectors = s->nr_sectors;
>  		return;
> @@ -105,7 +121,7 @@ static inline void
> blkif_get_x86_64_req(blkif_request_t *dst, blkif_x86_64_reque
>  	/* Prevent the compiler from using src->... instead. */
>  	barrier();
>  	if (dst->operation == BLKIF_OP_DISCARD) {
> -		struct blkif_request_discard *s = (void *)src;
> +                struct blkif_x86_64_request_discard *s = (void *)src;
>  		struct blkif_request_discard *d = (void *)dst;
>  		d->nr_sectors = s->nr_sectors;
>  		return;
> --
> 2.6.6
> 
> 
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Re: [Xen-devel] [PATCH] xen: fix qdisk BLKIF_OP_DISCARD for 32/64 word size mix

[Juergen Gross]

On 16/06/16 13:24, Paul Durrant wrote:
>> -----Original Message-----
>> From: Xen-devel [mailto:xen-devel-bounces@lists.xen.org] On Behalf Of
>> Juergen Gross
>> Sent: 16 June 2016 11:02
>> To: qemu-devel@nongnu.org; xen-devel@lists.xensource.com
>> Cc: Anthony Perard; Juergen Gross; sstabellini@kernel.org;
>> kraxel@redhat.com
>> Subject: [Xen-devel] [PATCH] xen: fix qdisk BLKIF_OP_DISCARD for 32/64
>> word size mix
>>
>> In case the word size of the domU and qemu running the qdisk backend
>> differ BLKIF_OP_DISCARD will not work reliably, as the request
>> structure in the ring have different layouts for different word size.
>>
>> Correct this by copying the request structure in case of different
>> word size element by element in the BLKIF_OP_DISCARD case, too.
>>
>> Signed-off-by: Juergen Gross <jgross@suse.com>
> 
> Would it not be better to re-import the canonical blkif header as a whole rather than cherry-picking like this? You'd need to post-process to maintain style and possibly change some names for compatibility etc. but probably nothing beyond what indent and a simple [s]ed script can do.
> I did broadly the same thing to re-import the netif header into Linux recently.

It's a little bit more than indent/sed, but nothing really scary.

I'll do it.


Juergen

Re: [Xen-devel] [PATCH] xen: fix qdisk BLKIF_OP_DISCARD for 32/64 word size mix

[Paul Durrant]

> -----Original Message-----
> From: Juergen Gross [mailto:jgross@suse.com]
> Sent: 16 June 2016 13:19
> To: Paul Durrant; qemu-devel@nongnu.org; xen-devel@lists.xensource.com
> Cc: Anthony Perard; sstabellini@kernel.org; kraxel@redhat.com
> Subject: Re: [Xen-devel] [PATCH] xen: fix qdisk BLKIF_OP_DISCARD for 32/64
> word size mix
> 
> On 16/06/16 13:24, Paul Durrant wrote:
> >> -----Original Message-----
> >> From: Xen-devel [mailto:xen-devel-bounces@lists.xen.org] On Behalf Of
> >> Juergen Gross
> >> Sent: 16 June 2016 11:02
> >> To: qemu-devel@nongnu.org; xen-devel@lists.xensource.com
> >> Cc: Anthony Perard; Juergen Gross; sstabellini@kernel.org;
> >> kraxel@redhat.com
> >> Subject: [Xen-devel] [PATCH] xen: fix qdisk BLKIF_OP_DISCARD for 32/64
> >> word size mix
> >>
> >> In case the word size of the domU and qemu running the qdisk backend
> >> differ BLKIF_OP_DISCARD will not work reliably, as the request
> >> structure in the ring have different layouts for different word size.
> >>
> >> Correct this by copying the request structure in case of different
> >> word size element by element in the BLKIF_OP_DISCARD case, too.
> >>
> >> Signed-off-by: Juergen Gross <jgross@suse.com>
> >
> > Would it not be better to re-import the canonical blkif header as a whole
> rather than cherry-picking like this? You'd need to post-process to maintain
> style and possibly change some names for compatibility etc. but probably
> nothing beyond what indent and a simple [s]ed script can do.
> > I did broadly the same thing to re-import the netif header into Linux
> recently.
> 
> It's a little bit more than indent/sed, but nothing really scary.
> 
> I'll do it.
>

Cool. The nice thing about bringing the header up-to-date is it pulls in all the newer comments and explanations too :-)
 
  Paul

> 
> Juergen

Re: [PATCH] xen: fix qdisk BLKIF_OP_DISCARD for 32/64 word size mix

[Stefano Stabellini]

On Thu, 16 Jun 2016, Juergen Gross wrote:
> On 16/06/16 12:54, Jan Beulich wrote:
> >>>> On 16.06.16 at 12:02, <JGross@suse.com> wrote:
> >> In case the word size of the domU and qemu running the qdisk backend
> >> differ BLKIF_OP_DISCARD will not work reliably, as the request
> >> structure in the ring have different layouts for different word size.
> >>
> >> Correct this by copying the request structure in case of different
> >> word size element by element in the BLKIF_OP_DISCARD case, too.
> >>
> >> Signed-off-by: Juergen Gross <jgross@suse.com>
> > 
> > With the indentation (tabs vs blanks) fixed
> 
> Hmm, qemu coding style is to use blanks. I could:
> a) leave the patch as is (changed lines indented with blanks)
> b) use tabs to indent (style of the modified file up to now)
> c) change the style of the file in this patch
> d) change the style of the file in a separate patch
> 
> Any preferences?

I would go with d), fixing it to conform with QEMU coding style.

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Re: [PATCH] xen: fix qdisk BLKIF_OP_DISCARD for 32/64 word size mix

[Juergen Gross]

On 16/06/16 15:07, Stefano Stabellini wrote:
> On Thu, 16 Jun 2016, Juergen Gross wrote:
>> On 16/06/16 12:54, Jan Beulich wrote:
>>>>>> On 16.06.16 at 12:02, <JGross@suse.com> wrote:
>>>> In case the word size of the domU and qemu running the qdisk backend
>>>> differ BLKIF_OP_DISCARD will not work reliably, as the request
>>>> structure in the ring have different layouts for different word size.
>>>>
>>>> Correct this by copying the request structure in case of different
>>>> word size element by element in the BLKIF_OP_DISCARD case, too.
>>>>
>>>> Signed-off-by: Juergen Gross <jgross@suse.com>
>>>
>>> With the indentation (tabs vs blanks) fixed
>>
>> Hmm, qemu coding style is to use blanks. I could:
>> a) leave the patch as is (changed lines indented with blanks)
>> b) use tabs to indent (style of the modified file up to now)
>> c) change the style of the file in this patch
>> d) change the style of the file in a separate patch
>>
>> Any preferences?
> 
> I would go with d), fixing it to conform with QEMU coding style.

As I'm about to resync the header with the Linux one as Paul suggested
it will be more like c). :-)


Juergen


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Re: [PATCH] xen: fix qdisk BLKIF_OP_DISCARD for 32/64 word size mix

[Stefano Stabellini]

On Thu, 16 Jun 2016, Juergen Gross wrote:
> On 16/06/16 15:07, Stefano Stabellini wrote:
> > On Thu, 16 Jun 2016, Juergen Gross wrote:
> >> On 16/06/16 12:54, Jan Beulich wrote:
> >>>>>> On 16.06.16 at 12:02, <JGross@suse.com> wrote:
> >>>> In case the word size of the domU and qemu running the qdisk backend
> >>>> differ BLKIF_OP_DISCARD will not work reliably, as the request
> >>>> structure in the ring have different layouts for different word size.
> >>>>
> >>>> Correct this by copying the request structure in case of different
> >>>> word size element by element in the BLKIF_OP_DISCARD case, too.
> >>>>
> >>>> Signed-off-by: Juergen Gross <jgross@suse.com>
> >>>
> >>> With the indentation (tabs vs blanks) fixed
> >>
> >> Hmm, qemu coding style is to use blanks. I could:
> >> a) leave the patch as is (changed lines indented with blanks)
> >> b) use tabs to indent (style of the modified file up to now)
> >> c) change the style of the file in this patch
> >> d) change the style of the file in a separate patch
> >>
> >> Any preferences?
> > 
> > I would go with d), fixing it to conform with QEMU coding style.
> 
> As I'm about to resync the header with the Linux one as Paul suggested
> it will be more like c). :-)
 
That's not a good idea, as you probably have noticed by now on the other
thread. This patch is OK, you just need to fix the intendation
separately.

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