From mboxrd@z Thu Jan  1 00:00:00 1970
From: Anthony Liguori <anthony@codemonkey.ws>
Subject: Re: [PATCH] virtio_ring: make structure defines packed
Date: Sat, 09 Feb 2008 18:51:14 -0600
Message-ID: <47AE4A82.3030504@codemonkey.ws>
References: <200802081401.21194.borntraeger@de.ibm.com>
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Cc: kvm-devel <kvm-devel@lists.sourceforge.net>,
	Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>,
	virtualization@lists.linux-foundation.org
To: Christian Borntraeger <borntraeger@de.ibm.com>
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Hi Christian,

Christian Borntraeger wrote:
>  struct vring_used
>  {
>  	__u16 flags;
>  	__u16 idx;
> +	__u32 padding;
>  	struct vring_used_elem ring[];
> -};
> +} __attribute__ ((packed));
>   

This padding that you've put in is not something that would normally 
occur on x86.  I've checked with GCC on 32-bit and 64-bit and neither 
would include that padding.  Is that padding included on s390?

I don't think we can do this on x86 at this point as it changes the 
ABI.  FWIW, I agree with Arnd also that we should not explicitly pad 
structures that are naturally aligned anyway.

Regards,

Anthony Liguori


>  struct vring {
>  	unsigned int num;
>
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