linux-kernel - Re: [PATCH] drivers/vfio: Fix an 8-byte alignment issue

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Message-ID: <20181017160354.6a732fa5@w520.home>
Date:   Wed, 17 Oct 2018 16:03:54 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:     Wenwen Wang <wang6495@....edu>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Kangjie Lu <kjlu@....edu>
Subject: Re: [PATCH] drivers/vfio: Fix an 8-byte alignment issue

On Wed, 17 Oct 2018 17:15:33 -0400
Konrad Rzeszutek Wilk <konrad.wilk@...cle.com> wrote:

> On Wed, Oct 17, 2018 at 01:18:19PM -0500, Wenwen Wang wrote:
> > This patch adds a 4-byte reserved field in the structure
> > vfio_eeh_pe_op to make sure that the u64 fields in the structure
> > vfio_eeh_pe_err are 8-byte aligned.  
> 
> Won't this break 32-bit kernels? That is the size of the structure
> will now be 4 bytes bigger..

Hi Konrad,

EEH support here depends on SPAPR_TCE_IOMMU which depends on either
PPC_POWERNV or PPC_PSERIES, both of which depend on PPC64.  So I don't
think 32-bit kernels are a concern here.  Thanks,

Alex
 
> > Signed-off-by: Wenwen Wang <wang6495@....edu>
> > ---
> >  include/uapi/linux/vfio.h | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> > index 1aa7b82..3e71ded 100644
> > --- a/include/uapi/linux/vfio.h
> > +++ b/include/uapi/linux/vfio.h
> > @@ -729,6 +729,7 @@ struct vfio_eeh_pe_op {
> >  	__u32 argsz;
> >  	__u32 flags;
> >  	__u32 op;
> > +	__u32 __res;
> >  	union {
> >  		struct vfio_eeh_pe_err err;
> >  	};
> > -- 
> > 2.7.4
> >