[Qemu-devel] Re: [patch uq/master 2/2] kvm-all.c: define smp_wmb and use it for coalesced mmio

[Marcelo Tosatti]

On Mon, Feb 22, 2010 at 04:23:32PM +0200, Avi Kivity wrote:
> On 02/22/2010 03:59 PM, Marcelo Tosatti wrote:
> >Cc: "Michael S. Tsirkin"<address@hidden>
> >Signed-off-by: Marcelo Tosatti<address@hidden>
> >
> >Index: qemu/kvm-all.c
> >===================================================================
> >--- qemu.orig/kvm-all.c
> >+++ qemu/kvm-all.c
> >@@ -718,6 +718,9 @@ static int kvm_handle_io(uint16_t port,
> >      return 1;
> >  }
> >
> >+/* FIXME: arch dependant, x86 version */
> >+#define smp_wmb()   asm volatile("" ::: "memory")
> >+
> 
> sfence?  

There is no need (for this case). Older read cannot be reordered with
write, writes are not reordered with other writes, writes by a single
processor are observed in the same order by all processors.

> what about other arches?

They need to be fixed? PPC needs an instruction apparently.

Is there any objection to including this patch?