pseries: Support SMT systems for KVM Book3S-HV

Alex Graf has already made qemu support KVM for the pseries machine
when using the Book3S-PR KVM variant (which runs the guest in
usermode, emulating supervisor operations).  This code allows gets us
very close to also working with KVM Book3S-HV (using the hypervisor
capabilities of recent POWER CPUs).

This patch moves us another step towards Book3S-HV support by
correctly handling SMT (multithreaded) POWER CPUs.  There are two
parts to this:

 * Querying KVM to check SMT capability, and if present, adjusting the
   cpu numbers that qemu assigns to cause KVM to assign guest threads
   to cores in the right way (this isn't automatic, because the POWER
   HV support has a limitation that different threads on a single core
   cannot be in different guests at the same time).

 * Correctly informing the guest OS of the SMT thread to core mappings
   via the device tree.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Alexander Graf <agraf@suse.de>

1 files changed, 21 insertions, 3 deletions

diff --git a/hw/spapr.c b/hw/spapr.c
index 63e5d33..c2675e1 100644
--- a/hw/spapr.c
+++ b/hw/spapr.c
@@ -29,6 +29,9 @@
 #include "elf.h"
 #include "net.h"
 #include "blockdev.h"
+#include "cpus.h"
+#include "kvm.h"
+#include "kvm_ppc.h"
 
 #include "hw/boards.h"
 #include "hw/ppc.h"
@@ -105,6 +108,7 @@ static void *spapr_create_fdt_skel(const char *cpu_model,
     uint32_t interrupt_server_ranges_prop[] = {0, cpu_to_be32(smp_cpus)};
     int i;
     char *modelname;
+    int smt = kvmppc_smt_threads();
 
 #define _FDT(exp) \
     do { \
@@ -164,13 +168,18 @@ static void *spapr_create_fdt_skel(const char *cpu_model,
 
     for (env = first_cpu; env != NULL; env = env->next_cpu) {
         int index = env->cpu_index;
-        uint32_t gserver_prop[] = {cpu_to_be32(index), 0}; /* HACK! */
+        uint32_t servers_prop[smp_threads];
+        uint32_t gservers_prop[smp_threads * 2];
         char *nodename;
         uint32_t segs[] = {cpu_to_be32(28), cpu_to_be32(40),
                            0xffffffff, 0xffffffff};
         uint32_t tbfreq = kvm_enabled() ? kvmppc_get_tbfreq() : TIMEBASE_FREQ;
         uint32_t cpufreq = kvm_enabled() ? kvmppc_get_clockfreq() : 1000000000;
 
+        if ((index % smt) != 0) {
+            continue;
+        }
+
         if (asprintf(&nodename, "%s@%x", modelname, index) < 0) {
             fprintf(stderr, "Allocation failure\n");
             exit(1);
@@ -195,9 +204,18 @@ static void *spapr_create_fdt_skel(const char *cpu_model,
                            pft_size_prop, sizeof(pft_size_prop))));
         _FDT((fdt_property_string(fdt, "status", "okay")));
         _FDT((fdt_property(fdt, "64-bit", NULL, 0)));
-        _FDT((fdt_property_cell(fdt, "ibm,ppc-interrupt-server#s", index)));
+
+        /* Build interrupt servers and gservers properties */
+        for (i = 0; i < smp_threads; i++) {
+            servers_prop[i] = cpu_to_be32(index + i);
+            /* Hack, direct the group queues back to cpu 0 */
+            gservers_prop[i*2] = cpu_to_be32(index + i);
+            gservers_prop[i*2 + 1] = 0;
+        }
+        _FDT((fdt_property(fdt, "ibm,ppc-interrupt-server#s",
+                           servers_prop, sizeof(servers_prop))));
         _FDT((fdt_property(fdt, "ibm,ppc-interrupt-gserver#s",
-                           gserver_prop, sizeof(gserver_prop))));
+                           gservers_prop, sizeof(gservers_prop))));
 
         if (env->mmu_model & POWERPC_MMU_1TSEG) {
             _FDT((fdt_property(fdt, "ibm,processor-segment-sizes",