Re: [RFC 7/11] virtio_pci: new, capability-aware driver.

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" [off-list ref] wrote:

quoted

On Thu, Dec 08, 2011 at 09:09:33PM +1030, Rusty Russell wrote:

quoted

+/* 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