linux-kernel - Re: [PATCH kernel] vfio: Add explicit alignments in vfio_iommu_spapr_tce

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Message-ID: <20151221005622.GR3011@voom.redhat.com>
Date:	Mon, 21 Dec 2015 11:56:22 +1100
From:	David Gibson <david@...son.dropbear.id.au>
To:	Alexey Kardashevskiy <aik@...abs.ru>
Cc:	Alex Williamson <alex.williamson@...hat.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
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 <aik@...abs.ru>

Oops, that was a bit sloppy.  Oh well.

Acked-by: David Gibson <david@...son.dropbear.id.au>

> ---
>  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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