Re: [PATCH] powerpc: Support lower minimum entitlement for virtual processors

[Robert Jennings <rcj@linux.vnet.ibm.com>]

* Benjamin Herrenschmidt (benh@kernel.crashing.org) wrote:
> On Fri, 2012-03-23 at 16:22 -0500, Robert Jennings wrote:
> > This patch changes the architecture vector to advertise support for a
> > lower minimum virtual processor entitled capacity.  The default
> > minimum without this patch is 10%, this patch specifies 5%.  This will
> > allow 20 LPARs per CPU rather than only 10.
> 
> Any reason why we don't just put 1% in there and thus don't have to
> change again when pHyp decides to lower their minimum ? :-)
> 
> (Can you test that it works, ie, that pHyp doesn't barf if we put 1% and
> properly uses 5% in that case ?)

Thanks Ben, makes good sense.
I'm in the process of validating this and I'll post reply or a new
version of the patch when I get it completed.

--Rob Jennings

> > Signed-off-by: Robert Jennings <rcj@linux.vnet.ibm.com>
> > ---
> >  arch/powerpc/kernel/prom_init.c |    8 ++++++--
> >  1 files changed, 6 insertions(+), 2 deletions(-)
> > 
> > diff --git a/arch/powerpc/kernel/prom_init.c b/arch/powerpc/kernel/prom_init.c
> > index eca626e..3d882ea 100644
> > --- a/arch/powerpc/kernel/prom_init.c
> > +++ b/arch/powerpc/kernel/prom_init.c
> > @@ -689,6 +689,9 @@ static void __init early_cmdline_parse(void)
> >  #define OV3_VMX			0x40	/* VMX/Altivec */
> >  #define OV3_DFP			0x20	/* decimal FP */
> >  
> > +/* Option vector 4: IBM PAPR implementation */
> > +#define OV4_MIN_ENT_CAP		0x05	/* minimum VP entitled capacity */
> > +
> >  /* Option vector 5: PAPR/OF options supported */
> >  #define OV5_LPAR		0x80	/* logical partitioning supported */
> >  #define OV5_SPLPAR		0x40	/* shared-processor LPAR supported */
> > @@ -753,8 +756,9 @@ static unsigned char ibm_architecture_vec[] = {
> >  	OV3_FP | OV3_VMX | OV3_DFP,
> >  
> >  	/* option vector 4: IBM PAPR implementation */
> > -	2 - 2,				/* length */
> > +	3 - 2,				/* length */
> >  	0,				/* don't halt */
> > +	OV4_MIN_ENT_CAP,		/* minimum VP entitled capacity */
> >  
> >  	/* option vector 5: PAPR/OF options */
> >  	13 - 2,				/* length */
> > @@ -771,7 +775,7 @@ static unsigned char ibm_architecture_vec[] = {
> >  	 * must match by the macro below. Update the definition if
> >  	 * the structure layout changes.
> >  	 */
> > -#define IBM_ARCH_VEC_NRCORES_OFFSET	100
> > +#define IBM_ARCH_VEC_NRCORES_OFFSET	101
> >  	W(NR_CPUS),			/* number of cores supported */
> >  
> >  	/* option vector 6: IBM PAPR hints */
> 
>