From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [RFC 7/11] virtio_pci: new, capability-aware driver.
Date: Mon, 12 Dec 2011 13:49:13 +0200
Message-ID: <20111212114912.GA7946@redhat.com>
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To: Rusty Russell <rusty@rustcorp.com.au>
Cc: Sasha Levin <levinsasha928@gmail.com>, virtualization <virtualization@lists.linux-foundation.org>
List-Id: virtualization@lists.linuxfoundation.org

On Mon, Dec 12, 2011 at 09:15:03AM +1030, Rusty Russell wrote:
> On Sun, 11 Dec 2011 11:42:56 +0200, "Michael S. Tsirkin" <mst@redhat.com> wrote:
> > On Thu, Dec 08, 2011 at 09:09:33PM +1030, Rusty Russell wrote:
> > > +/* There is no iowrite64.  We use two 32-bit ops. */
> > > +static void iowrite64(u64 val, const __le64 *addr)
> > > +{
> > > +	iowrite32((u32)val, (__le32 *)addr);
> > > +	iowrite32(val >> 32, (__le32 *)addr + 1);
> > > +}
> > > +
> > 
> > Let's put addr_lo/addr_hi in the structure then,
> > to make the fact this field is not atomic explicit?
> 
> Good point, assuming I haven't missed something.
> 
> Are 64-bit accesses actually unknown in PCI-land?  Or is this a limited
> availability thing?
> 
> Thanks,
> Rusty.

I think PCI can optionally support atomic 64 bit accesses, but not all
architectures can generate them.

-- 
MST