Re: [Qemu-devel] [PATCH] i386: Fix signedness of hyperv_spinlock_attempts

[Roman Kagan]

On Mon, Jun 17, 2019 at 11:23:01AM -0300, Eduardo Habkost wrote:
> On Mon, Jun 17, 2019 at 01:48:59PM +0000, Roman Kagan wrote:
> > On Sat, Jun 15, 2019 at 05:05:05PM -0300, Eduardo Habkost wrote:
> > > The current default value for hv-spinlocks is 0xFFFFFFFF (meaning
> > > "never retry").  However, the value is stored as a signed
> > > integer, making the getter of the hv-spinlocks QOM property
> > > return -1 instead of 0xFFFFFFFF.
> > > 
> > > Fix this by changing the type of X86CPU::hyperv_spinlock_attempts
> > > to uint32_t.  This has no visible effect to guest operating
> > > systems, affecting just the behavior of the QOM getter.
> > > 
> > > Signed-off-by: Eduardo Habkost <address@hidden>
> > > ---
> > >  target/i386/cpu.h | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > Reviewed-by: Roman Kagan <address@hidden>
> > 
> > That said, it's tempting to just nuke qdev_prop_spinlocks and make
> > hv-spinlocks a regular DEFINE_PROP_UINT32...
> 
> Agreed.  The only difference is that we would validate the
> property at realize time instead of object_property_set().

Right.  But currently it's validated to be no less than 0xfff and no
bigger than 0xffffffff.  The latter check would become unnecessary, and
I'm unable to find any reason to do the former (neither spec references
nor the log messages of the commits that introduced it).

Roman.