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

[Michael S. Tsirkin]

On Tue, Aug 28, 2012 at 09:02:05PM +0400, malc wrote:
> 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 <address@hidden> 
> > > 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 <address@hidden> 
> > > >> 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 
> > > >> >> <address@hidden> 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 <address@hidden>
> > > >> >> > ---
> > > >> >> >  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..]

It's still silly :)

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