Re: [for-5.0 1/4] spapr: Don't trigger a CAS reboot for XICS/XIVE mode changeover

[David Gibson <david@gibson.dropbear.id.au>]

[-- Attachment #1: Type: text/plain, Size: 4471 bytes --]

On Mon, Dec 02, 2019 at 08:50:09AM +0100, Greg Kurz wrote:
> On Fri, 29 Nov 2019 16:33:53 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > PAPR allows the interrupt controller used on a POWER9 machine (XICS or
> > XIVE) to be selected by the guest operating system, by using the
> > ibm,client-architecture-support (CAS) feature negotiation call.
> > 
> > Currently, if the guest selects an interrupt controller different from the
> > one selected at initial boot, this causes the system to be reset with the
> > new model and the boot starts again.  This means we run through the SLOF
> > boot process twice, as well as any other bootloader (e.g. grub) in use
> > before the OS calls CAS.  This can be confusing and/or inconvenient for
> > users.
> > 
> > Thanks to two fairly recent changes, we no longer need this reboot.  1) we
> > now completely regenerate the device tree when CAS is called (meaning we
> > don't need special case updates for all the device tree changes caused by
> > the interrupt controller mode change),  2) we now have explicit code paths
> > to activate and deactivate the different interrupt controllers, rather than
> > just implicitly calling those at machine reset time.
> > 
> > We can therefore eliminate the reboot for changing irq mode, simply by
> > putting a called to spapr_irq_update_active_intc() before we call
> 
> putting a call

Fixed, thanks.

> > spapr_h_cas_compose_response() (which gives the updated device tree to the
> > guest firmware and OS).
> > 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> 
> Convenient indeed ! :)
> 
> Reviewed-by: Greg Kurz <groug@kaod.org>
> 
> >  hw/ppc/spapr_hcall.c | 33 +++++++++++++--------------------
> >  1 file changed, 13 insertions(+), 20 deletions(-)
> > 
> > diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
> > index 140f05c1c6..05a7ca275b 100644
> > --- a/hw/ppc/spapr_hcall.c
> > +++ b/hw/ppc/spapr_hcall.c
> > @@ -1767,21 +1767,10 @@ static target_ulong h_client_architecture_support(PowerPCCPU *cpu,
> >      }
> >      spapr->cas_pre_isa3_guest = !spapr_ovec_test(ov1_guest, OV1_PPC_3_00);
> >      spapr_ovec_cleanup(ov1_guest);
> > -    if (!spapr->cas_reboot) {
> > -        /* If spapr_machine_reset() did not set up a HPT but one is necessary
> > -         * (because the guest isn't going to use radix) then set it up here. */
> > -        if ((spapr->patb_entry & PATE1_GR) && !guest_radix) {
> > -            /* legacy hash or new hash: */
> > -            spapr_setup_hpt_and_vrma(spapr);
> > -        }
> > -        spapr->cas_reboot =
> > -            (spapr_h_cas_compose_response(spapr, args[1], args[2],
> > -                                          ov5_updates) != 0);
> > -    }
> >  
> >      /*
> > -     * Ensure the guest asks for an interrupt mode we support; otherwise
> > -     * terminate the boot.
> > +     * Ensure the guest asks for an interrupt mode we support;
> > +     * otherwise terminate the boot.
> >       */
> >      if (guest_xive) {
> >          if (!spapr->irq->xive) {
> > @@ -1797,14 +1786,18 @@ static target_ulong h_client_architecture_support(PowerPCCPU *cpu,
> >          }
> >      }
> >  
> > -    /*
> > -     * Generate a machine reset when we have an update of the
> > -     * interrupt mode. Only required when the machine supports both
> > -     * modes.
> > -     */
> > +    spapr_irq_update_active_intc(spapr);
> > +
> >      if (!spapr->cas_reboot) {
> > -        spapr->cas_reboot = spapr_ovec_test(ov5_updates, OV5_XIVE_EXPLOIT)
> > -            && spapr->irq->xics && spapr->irq->xive;
> > +        /* If spapr_machine_reset() did not set up a HPT but one is necessary
> > +         * (because the guest isn't going to use radix) then set it up here. */
> > +        if ((spapr->patb_entry & PATE1_GR) && !guest_radix) {
> > +            /* legacy hash or new hash: */
> > +            spapr_setup_hpt_and_vrma(spapr);
> > +        }
> > +        spapr->cas_reboot =
> > +            (spapr_h_cas_compose_response(spapr, args[1], args[2],
> > +                                          ov5_updates) != 0);
> >      }
> >  
> >      spapr_ovec_cleanup(ov5_updates);
> 

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]