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Re: [for-5.0 1/4] spapr: Don't trigger a CAS reboot for XICS/XIVE mode c
From: |
Greg Kurz |
Subject: |
Re: [for-5.0 1/4] spapr: Don't trigger a CAS reboot for XICS/XIVE mode changeover |
Date: |
Mon, 2 Dec 2019 08:50:09 +0100 |
On Fri, 29 Nov 2019 16:33:53 +1100
David Gibson <address@hidden> 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
> spapr_h_cas_compose_response() (which gives the updated device tree to the
> guest firmware and OS).
>
> Signed-off-by: David Gibson <address@hidden>
> ---
Convenient indeed ! :)
Reviewed-by: Greg Kurz <address@hidden>
> 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);