Re: [Qemu-devel] [RFCv2 1/2] pseries: Fix incorrect calculation of threads per socket for chip-id

[Alexey Kardashevskiy]

On 09/04/2015 02:56 PM, David Gibson wrote:
> On Fri, Sep 04, 2015 at 02:51:39PM +1000, David Gibson wrote:
> > The device tree presented to pseries machine type guests includes an
> > ibm,chip-id property which gives essentially the socket number of each
> > vcpu core (individual vcpu threads don't get a node in the device
> > tree).
> >
> > To calculate this, it uses a vcpus_per_socket variable computed as
> > (smp_cpus / #sockets).  This is correct for the usual case where
> > smp_cpus == smp_threads * smp_cores * #sockets.
> >
> > However, you can start QEMU with the number of cores and threads
> > mismatching the total number of vcpus (whether that _should_ be
> > permitted is a topic for another day).  It's a bit hard to say what
> > the "real" number of vcpus per socket here is, but for most purposes
> > (smp_threads * smp_cores) will more meaningfully match how QEMU
> > behaves with respect to socket boundaries.
> >
> > Signed-off-by: David Gibson <address@hidden>
>
> Gah, sorry, there's a compile error in this.  I got sidetracked
> between writing and posting and forgot I hadn't fixed it yet.

The error, I believe, is "opts" not being used anymore?
If so,

Reviewed-by: Alexey Kardashevskiy <address@hidden>        


> > ---
> >   hw/ppc/spapr.c | 5 ++---
> >   1 file changed, 2 insertions(+), 3 deletions(-)
> >
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index 783763f..dbc295b 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -595,8 +595,7 @@ static void spapr_populate_cpu_dt(CPUState *cs, void *fdt, 
> > int offset,
> >       uint32_t page_sizes_prop[64];
> >       size_t page_sizes_prop_size;
> >       QemuOpts *opts = qemu_opts_find(qemu_find_opts("smp-opts"), NULL);
> > -    unsigned sockets = opts ? qemu_opt_get_number(opts, "sockets", 0) : 0;
> > -    uint32_t cpus_per_socket = sockets ? (smp_cpus / sockets) : 1;
> > +    uint32_t vcpus_per_socket = smp_threads * smp_cores;
> >       uint32_t pft_size_prop[] = {0, cpu_to_be32(spapr->htab_shift)};
> >
> >       _FDT((fdt_setprop_cell(fdt, offset, "reg", index)));
> > @@ -665,7 +664,7 @@ static void spapr_populate_cpu_dt(CPUState *cs, void *fdt, 
> > int offset,
> >       }
> >
> >       _FDT((fdt_setprop_cell(fdt, offset, "ibm,chip-id",
> > -                           cs->cpu_index / cpus_per_socket)));
> > +                           cs->cpu_index / vcpus_per_socket)));
> >
> >       _FDT((fdt_setprop(fdt, offset, "ibm,pft-size",
> >                         pft_size_prop, sizeof(pft_size_prop))));


--
Alexey