From: Greg Kurz <groug@kaod.org>

According to the description of "ibm,client-architecture-support" that
can found in LoPAPR "B.6.2.3 Root Node Methods":

If multiple partition processors or threads are active at the time of
the ibm,client-architecture-support method call, or an error is detected
in the format of the ibm,architecture.vec structure, the err? boolean
shall be TRUE; else FALSE.

We certainly don't want to temper with the platform or with the PCR of
the other vCPUs if they happen to be active. Ensure we have only one
active vCPU and fail CAS otherwise. This is just for conformance and
robustness, it doesn't fix any known bugs.

Signed-off-by: Greg Kurz <groug@kaod.org>
Message-Id: <157969867170.571404.12117797348882189656.stgit@bahia.lan>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 hw/ppc/spapr_hcall.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
index ffb14641f9..b8bb66b5c0 100644
--- a/hw/ppc/spapr_hcall.c
+++ b/hw/ppc/spapr_hcall.c
@@ -1676,6 +1676,18 @@ static target_ulong h_client_architecture_support(PowerPCCPU *cpu,
     Error *local_err = NULL;
     bool raw_mode_supported = false;
     bool guest_xive;
+    CPUState *cs;
+
+    /* CAS is supposed to be called early when only the boot vCPU is active. */
+    CPU_FOREACH(cs) {
+        if (cs == CPU(cpu)) {
+            continue;
+        }
+        if (!cs->halted) {
+            warn_report("guest has multiple active vCPUs at CAS, which is not allowed");
+            return H_MULTI_THREADS_ACTIVE;
+        }
+    }
 
     cas_pvr = cas_check_pvr(spapr, cpu, &addr, &raw_mode_supported, &local_err);
     if (local_err) {
-- 
2.24.1