Re: [Qemu-devel] [PATCHv2 3/4] cpuid: disable pv eoi for 1.1 and older compat types

[malc <av1474@comtv.ru>]

On Tue, 28 Aug 2012, Michael S. Tsirkin wrote:

> On Mon, Aug 27, 2012 at 07:40:56PM +0000, Blue Swirl wrote:
> > On Mon, Aug 27, 2012 at 7:24 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
> > > On Mon, Aug 27, 2012 at 07:12:27PM +0000, Blue Swirl wrote:
> > >> On Mon, Aug 27, 2012 at 7:06 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
> > >> > On Mon, Aug 27, 2012 at 06:58:29PM +0000, Blue Swirl wrote:
> > >> >> On Mon, Aug 27, 2012 at 12:20 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
> > >> >> > In preparation for adding PV EOI support, disable PV EOI by default for
> > >> >> > 1.1 and older machine types, to avoid CPUID changing during migration.
> > >> >> >
> > >> >> > PV EOI can still be enabled/disabled by specifying it explicitly.
> > >> >> >     Enable for 1.1
> > >> >> >     -M pc-1.1 -cpu kvm64,+kvm_pv_eoi
> > >> >> >     Disable for 1.2
> > >> >> >     -M pc-1.2 -cpu kvm64,-kvm_pv_eoi
> > >> >> >
> > >> >> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > >> >> > ---
> > >> >> >  hw/Makefile.objs  |  2 +-
> > >> >> >  hw/cpu_flags.c    | 32 ++++++++++++++++++++++++++++++++
> > >> >> >  hw/cpu_flags.h    |  9 +++++++++
> > >> >> >  hw/pc_piix.c      |  2 ++

[..snip..]

> > 
> > No leading underscores. They are not used in QEMU.
> 
> They are *widely* used in QEMU to mark internal
> stuff. E.g. parameters in many macros.
> 

ISO/IEC 9899:TC3 7.1.3#1

- All identifiers that begin with an underscore and either an
  uppercase letter or another underscore are always reserved for any use.

IOW no __ or _[A-Z] at all.

- All identifiers that begin with an underscore are always reserved
  for use as identifiers with file scope in both the ordinary and tag
  name spaces.

IOW _ as the name of an argument to a macro is (probably) okay.

> In reality __ is also widely used. I'm still mulling
> removing 2.4 from HACKING - it appears too draconian,
> the chances of a conflict with preprocessor are remote
> and if it triggers, it's trivial to catch.
> We also have lots of existing code violating this rule.
> 
> And the rule about _t suffix is just silly.

http://pubs.opengroup.org/onlinepubs/7908799/xns/namespace.html

[..snip..]

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