spapr: add a 'reset' method to the sPAPR IRQ backend

For the time being, the XIVE reset handler updates the OS CAM line of
the vCPU as it is done under a real hypervisor when a vCPU is
scheduled to run on a HW thread. This will let the XIVE presenter
engine find a match among the NVTs dispatched on the HW threads.

This handler will become even more useful when we introduce the
machine supporting both interrupt modes, XIVE and XICS. In this
machine, the interrupt mode is chosen by the CAS negotiation process
and activated after a reset.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
[dwg: Fix style nits]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

hw/intc/spapr_xive.c

@@ -179,6 +179,23 @@ static void spapr_xive_map_mmio(sPAPRXive *xive)
     sysbus_mmio_map(SYS_BUS_DEVICE(xive), 2, xive->tm_base);
 }
 
+/*
+ * When a Virtual Processor is scheduled to run on a HW thread, the
+ * hypervisor pushes its identifier in the OS CAM line. Emulate the
+ * same behavior under QEMU.
+ */
+void spapr_xive_set_tctx_os_cam(XiveTCTX *tctx)
+{
+    uint8_t  nvt_blk;
+    uint32_t nvt_idx;
+    uint32_t nvt_cam;
+
+    spapr_xive_cpu_to_nvt(POWERPC_CPU(tctx->cs), &nvt_blk, &nvt_idx);
+
+    nvt_cam = cpu_to_be32(TM_QW1W2_VO | xive_nvt_cam_line(nvt_blk, nvt_idx));
+    memcpy(&tctx->regs[TM_QW1_OS + TM_WORD2], &nvt_cam, 4);
+}
+
 static void spapr_xive_end_reset(XiveEND *end)
 {
     memset(end, 0, sizeof(*end));

hw/ppc/spapr.c

@@ -1619,6 +1619,12 @@ static void spapr_machine_reset(void)
 
     qemu_devices_reset();
 
+    /*
+     * This is fixing some of the default configuration of the XIVE
+     * devices. To be called after the reset of the machine devices.
+     */
+    spapr_irq_reset(spapr, &error_fatal);
+
     /* DRC reset may cause a device to be unplugged. This will cause troubles
      * if this device is used by another device (eg, a running vhost backend
      * will crash QEMU if the DIMM holding the vring goes away). To avoid such

hw/ppc/spapr_irq.c

@@ -305,7 +305,14 @@ static void spapr_irq_print_info_xive(sPAPRMachineState *spapr,
 static Object *spapr_irq_cpu_intc_create_xive(sPAPRMachineState *spapr,
                                               Object *cpu, Error **errp)
 {
-    return xive_tctx_create(cpu, XIVE_ROUTER(spapr->xive), errp);
+    Object *obj = xive_tctx_create(cpu, XIVE_ROUTER(spapr->xive), errp);
+
+    /*
+     * (TCG) Early setting the OS CAM line for hotplugged CPUs as they
+     * don't benificiate from the reset of the XIVE IRQ backend
+     */
+    spapr_xive_set_tctx_os_cam(XIVE_TCTX(obj));
+    return obj;
 }
 
 static int spapr_irq_post_load_xive(sPAPRMachineState *spapr, int version_id)
@@ -313,6 +320,18 @@ static int spapr_irq_post_load_xive(sPAPRMachineState *spapr, int version_id)
     return 0;
 }
 
+static void spapr_irq_reset_xive(sPAPRMachineState *spapr, Error **errp)
+{
+    CPUState *cs;
+
+    CPU_FOREACH(cs) {
+        PowerPCCPU *cpu = POWERPC_CPU(cs);
+
+        /* (TCG) Set the OS CAM line of the thread interrupt context. */
+        spapr_xive_set_tctx_os_cam(XIVE_TCTX(cpu->intc));
+    }
+}
+
 /*
  * XIVE uses the full IRQ number space. Set it to 8K to be compatible
  * with XICS.
@@ -333,6 +352,7 @@ sPAPRIrq spapr_irq_xive = {
     .dt_populate = spapr_dt_xive,
     .cpu_intc_create = spapr_irq_cpu_intc_create_xive,
     .post_load   = spapr_irq_post_load_xive,
+    .reset       = spapr_irq_reset_xive,
 };
 
 /*
@@ -378,6 +398,15 @@ int spapr_irq_post_load(sPAPRMachineState *spapr, int version_id)
     return smc->irq->post_load(spapr, version_id);
 }
 
+void spapr_irq_reset(sPAPRMachineState *spapr, Error **errp)
+{
+    sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(spapr);
+
+    if (smc->irq->reset) {
+        smc->irq->reset(spapr, errp);
+    }
+}
+
 /*
  * XICS legacy routines - to deprecate one day
  */

include/hw/ppc/spapr_irq.h

@@ -44,6 +44,7 @@ typedef struct sPAPRIrq {
     Object *(*cpu_intc_create)(sPAPRMachineState *spapr, Object *cpu,
                                Error **errp);
     int (*post_load)(sPAPRMachineState *spapr, int version_id);
+    void (*reset)(sPAPRMachineState *spapr, Error **errp);
 } sPAPRIrq;
 
 extern sPAPRIrq spapr_irq_xics;
@@ -55,6 +56,7 @@ int spapr_irq_claim(sPAPRMachineState *spapr, int irq, bool lsi, Error **errp);
 void spapr_irq_free(sPAPRMachineState *spapr, int irq, int num);
 qemu_irq spapr_qirq(sPAPRMachineState *spapr, int irq);
 int spapr_irq_post_load(sPAPRMachineState *spapr, int version_id);
+void spapr_irq_reset(sPAPRMachineState *spapr, Error **errp);
 
 /*
  * XICS legacy routines

include/hw/ppc/spapr_xive.h

@@ -47,5 +47,6 @@ typedef struct sPAPRMachineState sPAPRMachineState;
 void spapr_xive_hcall_init(sPAPRMachineState *spapr);
 void spapr_dt_xive(sPAPRMachineState *spapr, uint32_t nr_servers, void *fdt,
                    uint32_t phandle);
+void spapr_xive_set_tctx_os_cam(XiveTCTX *tctx);
 
 #endif /* PPC_SPAPR_XIVE_H */