2015-12-18 01:37:04

by Alexey Kardashevskiy

[permalink] [raw]
Subject: [PATCH kernel] vfio: Add explicit alignments in vfio_iommu_spapr_tce_create

The vfio_iommu_spapr_tce_create struct has 4x32bit and 2x64bit fields
which should have resulted in sizeof(fio_iommu_spapr_tce_create) equal
to 32 bytes. However due to the gcc's default alignment, the actual
size of this struct is 40 bytes.

This fills gaps with __resv1/2 fields.

This should not cause any change in behavior.

Signed-off-by: Alexey Kardashevskiy <[email protected]>
---
include/uapi/linux/vfio.h | 2 ++
1 file changed, 2 insertions(+)

diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 9fd7b5d..d117233 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -568,8 +568,10 @@ struct vfio_iommu_spapr_tce_create {
__u32 flags;
/* in */
__u32 page_shift;
+ __u32 __resv1;
__u64 window_size;
__u32 levels;
+ __u32 __resv2;
/* out */
__u64 start_addr;
};
--
2.5.0.rc3


2015-12-21 00:59:47

by David Gibson

[permalink] [raw]
Subject: Re: [PATCH kernel] vfio: Add explicit alignments in vfio_iommu_spapr_tce_create

On Fri, Dec 18, 2015 at 12:35:47PM +1100, Alexey Kardashevskiy wrote:
> The vfio_iommu_spapr_tce_create struct has 4x32bit and 2x64bit fields
> which should have resulted in sizeof(fio_iommu_spapr_tce_create) equal
> to 32 bytes. However due to the gcc's default alignment, the actual
> size of this struct is 40 bytes.
>
> This fills gaps with __resv1/2 fields.
>
> This should not cause any change in behavior.
>
> Signed-off-by: Alexey Kardashevskiy <[email protected]>

Oops, that was a bit sloppy. Oh well.

Acked-by: David Gibson <[email protected]>

> ---
> include/uapi/linux/vfio.h | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 9fd7b5d..d117233 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -568,8 +568,10 @@ struct vfio_iommu_spapr_tce_create {
> __u32 flags;
> /* in */
> __u32 page_shift;
> + __u32 __resv1;
> __u64 window_size;
> __u32 levels;
> + __u32 __resv2;
> /* out */
> __u64 start_addr;
> };

--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson

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2015-12-22 20:09:40

by Alex Williamson

[permalink] [raw]
Subject: Re: [PATCH kernel] vfio: Add explicit alignments in vfio_iommu_spapr_tce_create

On Fri, 2015-12-18 at 12:35 +1100, Alexey Kardashevskiy wrote:
> The vfio_iommu_spapr_tce_create struct has 4x32bit and 2x64bit fields
> which should have resulted in sizeof(fio_iommu_spapr_tce_create)
> equal
> to 32 bytes. However due to the gcc's default alignment, the actual
> size of this struct is 40 bytes.
>
> This fills gaps with __resv1/2 fields.
>
> This should not cause any change in behavior.
>
> Signed-off-by: Alexey Kardashevskiy <[email protected]>
> ---

Applied to next for v4.5 with David's ack.  Thanks!

Alex

>  include/uapi/linux/vfio.h | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 9fd7b5d..d117233 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -568,8 +568,10 @@ struct vfio_iommu_spapr_tce_create {
>   __u32 flags;
>   /* in */
>   __u32 page_shift;
> + __u32 __resv1;
>   __u64 window_size;
>   __u32 levels;
> + __u32 __resv2;
>   /* out */
>   __u64 start_addr;
>  };