diff mbox series

[PULL,02/72] ppc/spapr: Add ibm,pi-features

Message ID 20240523230747.45703-3-npiggin@gmail.com
State New
Headers show
Series [PULL,01/72] spapr: avoid overhead of finding vhyp class in critical operations | expand

Commit Message

Nicholas Piggin May 23, 2024, 11:06 p.m. UTC 
The ibm,pi-features property has a bit to say whether or not
msgsndp should be used. Linux checks if it is being run under
KVM and avoids msgsndp anyway, but it would be preferable to
rely on this bit.

Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 hw/ppc/spapr.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)
diff mbox series

Patch

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index d2d1e310a3..4345764bce 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -353,6 +353,32 @@  static void spapr_dt_pa_features(SpaprMachineState *spapr,
     _FDT((fdt_setprop(fdt, offset, "ibm,pa-features", pa_features, pa_size)));
 }
 
+static void spapr_dt_pi_features(SpaprMachineState *spapr,
+                                 PowerPCCPU *cpu,
+                                 void *fdt, int offset)
+{
+    uint8_t pi_features[] = { 1, 0,
+        0x00 };
+
+    if (kvm_enabled() && ppc_check_compat(cpu, CPU_POWERPC_LOGICAL_3_00,
+                                          0, cpu->compat_pvr)) {
+        /*
+         * POWER9 and later CPUs with KVM run in LPAR-per-thread mode where
+         * all threads are essentially independent CPUs, and msgsndp does not
+         * work (because it is physically-addressed) and therefore is
+         * emulated by KVM, so disable it here to ensure XIVE will be used.
+         * This is both KVM and CPU implementation-specific behaviour so a KVM
+         * cap would be cleanest, but for now this works. If KVM ever permits
+         * native msgsndp execution by guests, a cap could be added at that
+         * time.
+         */
+        pi_features[2] |= 0x08; /* 4: No msgsndp */
+    }
+
+    _FDT((fdt_setprop(fdt, offset, "ibm,pi-features", pi_features,
+                      sizeof(pi_features))));
+}
+
 static hwaddr spapr_node0_size(MachineState *machine)
 {
     if (machine->numa_state->num_nodes) {
@@ -815,6 +841,8 @@  static void spapr_dt_cpu(CPUState *cs, void *fdt, int offset,
 
     spapr_dt_pa_features(spapr, cpu, fdt, offset);
 
+    spapr_dt_pi_features(spapr, cpu, fdt, offset);
+
     _FDT((fdt_setprop_cell(fdt, offset, "ibm,chip-id",
                            cs->cpu_index / vcpus_per_socket)));