From: David Gibson <david@gibson.dropbear.id.au>

Date: Fri, 18 Oct 2019 15:19:31 +1100

Subject: [PATCH] spapr: Don't trigger a CAS reboot for XICS/XIVE mode

 changeover

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 call to spapr_irq_update_active_intc() before we call

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>

Reviewed-by: Cedric Le Goater <clg@fr.ibm.com>

Reviewed-by: Greg Kurz <groug@kaod.org>

(cherry picked from commit 8deb8019d696c75e6ecaee7545026b62aba2f1bb)

---

 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);