Re: [Qemu-devel] [PATCH 1/2] dma-helpers: explicitly pass alignment into dma-helpers
On 10/12/2016 06:22 AM, Kevin Wolf wrote:
Am 11.10.2016 um 17:47 hat John Snow geschrieben:
On 10/10/2016 03:23 PM, Mark Cave-Ayland wrote:
On 10/10/16 17:34, Eric Blake wrote:
On 10/09/2016 11:43 AM, Mark Cave-Ayland wrote:
The hard-coded default alignment is BDRV_SECTOR_SIZE, however this is not
necessarily the case for all platforms. Use this as the default alignment for
all current callers.
Signed-off-by: Mark Cave-Ayland
---
@@ -160,8 +161,8 @@ static void dma_blk_cb(void *opaque, int ret)
return;
}
-if (dbs->iov.size & ~BDRV_SECTOR_MASK) {
-qemu_iovec_discard_back(&dbs->iov, dbs->iov.size & ~BDRV_SECTOR_MASK);
+if (dbs->iov.size & (dbs->align - 1)) {
+qemu_iovec_discard_back(&dbs->iov, dbs->iov.size & (dbs->align - 1));
Would it be any smarter to use osdep.h's QEMU_IS_ALIGNED(dbs->iov.size,
dbs->align) and QEMU_ALIGN_DOWN(dbs->iov.size, dbs->align)?
Semantically it is the same, but the macros make it obvious what the
bit-twiddling is doing.
Unless you think that needs a tweak,
Reviewed-by: Eric Blake
I can't say I feel too strongly about it since there are plenty of other
examples of this style in the codebase, so I'm happy to go with whatever
John/Paolo are most happy with.
ATB,
Mark.
I can't pretend I am consistent, but when in doubt use the macro.
Not worth a respin IMO, but I think this falls out of my
jurisdiction :)
Acked-by: John Snow
dma-helpers.c is officially unmaintained, and as the other patch is
clearly IDE, I think the series should go through your tree.
Kevin
Oh! I was under the impression that Paolo had the dma-helpers. My
mistake. I will test and stage this.
--js
Re: [Qemu-devel] [PATCH 1/2] dma-helpers: explicitly pass alignment into dma-helpers
Am 11.10.2016 um 17:47 hat John Snow geschrieben:
> On 10/10/2016 03:23 PM, Mark Cave-Ayland wrote:
> >On 10/10/16 17:34, Eric Blake wrote:
> >
> >>On 10/09/2016 11:43 AM, Mark Cave-Ayland wrote:
> >>>The hard-coded default alignment is BDRV_SECTOR_SIZE, however this is not
> >>>necessarily the case for all platforms. Use this as the default alignment
> >>>for
> >>>all current callers.
> >>>
> >>>Signed-off-by: Mark Cave-Ayland
> >>>---
> >>
> >>>@@ -160,8 +161,8 @@ static void dma_blk_cb(void *opaque, int ret)
> >>> return;
> >>> }
> >>>
> >>>-if (dbs->iov.size & ~BDRV_SECTOR_MASK) {
> >>>-qemu_iovec_discard_back(&dbs->iov, dbs->iov.size &
> >>>~BDRV_SECTOR_MASK);
> >>>+if (dbs->iov.size & (dbs->align - 1)) {
> >>>+qemu_iovec_discard_back(&dbs->iov, dbs->iov.size & (dbs->align -
> >>>1));
> >>
> >>Would it be any smarter to use osdep.h's QEMU_IS_ALIGNED(dbs->iov.size,
> >>dbs->align) and QEMU_ALIGN_DOWN(dbs->iov.size, dbs->align)?
> >>Semantically it is the same, but the macros make it obvious what the
> >>bit-twiddling is doing.
> >>
> >>Unless you think that needs a tweak,
> >>Reviewed-by: Eric Blake
> >
> >I can't say I feel too strongly about it since there are plenty of other
> >examples of this style in the codebase, so I'm happy to go with whatever
> >John/Paolo are most happy with.
> >
> >
> >ATB,
> >
> >Mark.
> >
>
> I can't pretend I am consistent, but when in doubt use the macro.
> Not worth a respin IMO, but I think this falls out of my
> jurisdiction :)
>
> Acked-by: John Snow
dma-helpers.c is officially unmaintained, and as the other patch is
clearly IDE, I think the series should go through your tree.
Kevin
Re: [Qemu-devel] [PATCH 1/2] dma-helpers: explicitly pass alignment into dma-helpers
On 10/10/2016 03:23 PM, Mark Cave-Ayland wrote:
On 10/10/16 17:34, Eric Blake wrote:
On 10/09/2016 11:43 AM, Mark Cave-Ayland wrote:
The hard-coded default alignment is BDRV_SECTOR_SIZE, however this is not
necessarily the case for all platforms. Use this as the default alignment for
all current callers.
Signed-off-by: Mark Cave-Ayland
---
@@ -160,8 +161,8 @@ static void dma_blk_cb(void *opaque, int ret)
return;
}
-if (dbs->iov.size & ~BDRV_SECTOR_MASK) {
-qemu_iovec_discard_back(&dbs->iov, dbs->iov.size & ~BDRV_SECTOR_MASK);
+if (dbs->iov.size & (dbs->align - 1)) {
+qemu_iovec_discard_back(&dbs->iov, dbs->iov.size & (dbs->align - 1));
Would it be any smarter to use osdep.h's QEMU_IS_ALIGNED(dbs->iov.size,
dbs->align) and QEMU_ALIGN_DOWN(dbs->iov.size, dbs->align)?
Semantically it is the same, but the macros make it obvious what the
bit-twiddling is doing.
Unless you think that needs a tweak,
Reviewed-by: Eric Blake
I can't say I feel too strongly about it since there are plenty of other
examples of this style in the codebase, so I'm happy to go with whatever
John/Paolo are most happy with.
ATB,
Mark.
I can't pretend I am consistent, but when in doubt use the macro. Not
worth a respin IMO, but I think this falls out of my jurisdiction :)
Acked-by: John Snow
Re: [Qemu-devel] [PATCH 1/2] dma-helpers: explicitly pass alignment into dma-helpers
On 10/10/16 17:34, Eric Blake wrote:
> On 10/09/2016 11:43 AM, Mark Cave-Ayland wrote:
>> The hard-coded default alignment is BDRV_SECTOR_SIZE, however this is not
>> necessarily the case for all platforms. Use this as the default alignment for
>> all current callers.
>>
>> Signed-off-by: Mark Cave-Ayland
>> ---
>
>> @@ -160,8 +161,8 @@ static void dma_blk_cb(void *opaque, int ret)
>> return;
>> }
>>
>> -if (dbs->iov.size & ~BDRV_SECTOR_MASK) {
>> -qemu_iovec_discard_back(&dbs->iov, dbs->iov.size &
>> ~BDRV_SECTOR_MASK);
>> +if (dbs->iov.size & (dbs->align - 1)) {
>> +qemu_iovec_discard_back(&dbs->iov, dbs->iov.size & (dbs->align -
>> 1));
>
> Would it be any smarter to use osdep.h's QEMU_IS_ALIGNED(dbs->iov.size,
> dbs->align) and QEMU_ALIGN_DOWN(dbs->iov.size, dbs->align)?
> Semantically it is the same, but the macros make it obvious what the
> bit-twiddling is doing.
>
> Unless you think that needs a tweak,
> Reviewed-by: Eric Blake
I can't say I feel too strongly about it since there are plenty of other
examples of this style in the codebase, so I'm happy to go with whatever
John/Paolo are most happy with.
ATB,
Mark.
Re: [Qemu-devel] [PATCH 1/2] dma-helpers: explicitly pass alignment into dma-helpers
On 10/09/2016 11:43 AM, Mark Cave-Ayland wrote:
> The hard-coded default alignment is BDRV_SECTOR_SIZE, however this is not
> necessarily the case for all platforms. Use this as the default alignment for
> all current callers.
>
> Signed-off-by: Mark Cave-Ayland
> ---
> @@ -160,8 +161,8 @@ static void dma_blk_cb(void *opaque, int ret)
> return;
> }
>
> -if (dbs->iov.size & ~BDRV_SECTOR_MASK) {
> -qemu_iovec_discard_back(&dbs->iov, dbs->iov.size &
> ~BDRV_SECTOR_MASK);
> +if (dbs->iov.size & (dbs->align - 1)) {
> +qemu_iovec_discard_back(&dbs->iov, dbs->iov.size & (dbs->align - 1));
Would it be any smarter to use osdep.h's QEMU_IS_ALIGNED(dbs->iov.size,
dbs->align) and QEMU_ALIGN_DOWN(dbs->iov.size, dbs->align)?
Semantically it is the same, but the macros make it obvious what the
bit-twiddling is doing.
Unless you think that needs a tweak,
Reviewed-by: Eric Blake
--
Eric Blake eblake redhat com+1-919-301-3266
Libvirt virtualization library http://libvirt.org
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