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>

1 files changed, 17 insertions, 0 deletions

diff --git a/hw/intc/spapr_xive.c b/hw/intc/spapr_xive.c
index 682c192268..0e39c90cbd 100644
--- a/hw/intc/spapr_xive.c
+++ b/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));