[Qemu-devel] [PATCH 1/4] target-ppc: Add hooks for handling tcg and kvm limitations

[David Gibson <david@gibson.dropbear.id.au>]

On target-ppc, our table of CPU types and features encodes the features as
found on the hardware, regardless of whether these features are actually
usable under TCG or KVM.  We already have cases where the information from
the cpu table must be fixed up to account for limitations in the emulation
method we're using.  e.g. TCG does not support the DFP and VSX instructions
and KVM needs different numbering of the CPUs in order to tell it the
correct thread to core mappings.

This patch cleans up these hacks to handle emulation limitations by
consolidating them into a pair of functions specifically for the purpose.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 target-ppc/helper.c         |    9 -------
 target-ppc/kvm.c            |   14 +++++++++++
 target-ppc/kvm_ppc.h        |    5 ++++
 target-ppc/translate_init.c |   51 +++++++++++++++++++++++++++++-------------
 4 files changed, 54 insertions(+), 25 deletions(-)

diff --git a/target-ppc/helper.c b/target-ppc/helper.c
index 39dcc27..ef8fe28 100644
--- a/target-ppc/helper.c
+++ b/target-ppc/helper.c
@@ -3198,15 +3198,6 @@ CPUPPCState *cpu_ppc_init (const char *cpu_model)
     if (tcg_enabled()) {
         ppc_translate_init();
     }
-    /* Adjust cpu index for SMT */
-#if !defined(CONFIG_USER_ONLY)
-    if (kvm_enabled()) {
-        int smt = kvmppc_smt_threads();
-
-        env->cpu_index = (env->cpu_index / smp_threads)*smt
-            + (env->cpu_index % smp_threads);
-    }
-#endif /* !CONFIG_USER_ONLY */
     env->cpu_model_str = cpu_model;
     cpu_ppc_register_internal(env, def);
 
diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
index 724f4c7..8b49761 100644
--- a/target-ppc/kvm.c
+++ b/target-ppc/kvm.c
@@ -27,6 +27,7 @@
 #include "kvm.h"
 #include "kvm_ppc.h"
 #include "cpu.h"
+#include "cpus.h"
 #include "device_tree.h"
 #include "hw/sysbus.h"
 #include "hw/spapr.h"
@@ -938,6 +939,19 @@ const ppc_def_t *kvmppc_host_cpu_def(void)
     return spec;
 }
 
+int kvm_fixup_ppc_env(CPUPPCState *env, const ppc_def_t *def)
+{
+    int smt;
+
+    /* Adjust cpu index for SMT */
+    smt = kvmppc_smt_threads();
+    env->cpu_index = (env->cpu_index / smp_threads)*smt
+        + (env->cpu_index % smp_threads);
+
+    return 0;
+}
+
+
 bool kvm_arch_stop_on_emulation_error(CPUPPCState *env)
 {
     return true;
diff --git a/target-ppc/kvm_ppc.h b/target-ppc/kvm_ppc.h
index 8f1267c..9940e39 100644
--- a/target-ppc/kvm_ppc.h
+++ b/target-ppc/kvm_ppc.h
@@ -29,6 +29,7 @@ void *kvmppc_create_spapr_tce(uint32_t liobn, uint32_t window_size, int *pfd);
 int kvmppc_remove_spapr_tce(void *table, int pfd, uint32_t window_size);
 #endif /* !CONFIG_USER_ONLY */
 const ppc_def_t *kvmppc_host_cpu_def(void);
+int kvm_fixup_ppc_env(CPUPPCState *env, const ppc_def_t *def);
 
 #else
 
@@ -95,6 +96,10 @@ static inline const ppc_def_t *kvmppc_host_cpu_def(void)
     return NULL;
 }
 
+static inline int kvm_fixup_ppc_env(CPUPPCState *env, const ppc_def_t *def)
+{
+    return -1;
+}
 #endif
 
 #ifndef CONFIG_KVM
diff --git a/target-ppc/translate_init.c b/target-ppc/translate_init.c
index 367eefa..bbdf174 100644
--- a/target-ppc/translate_init.c
+++ b/target-ppc/translate_init.c
@@ -9889,6 +9889,28 @@ static int gdb_set_spe_reg(CPUPPCState *env, uint8_t *mem_buf, int n)
     return 0;
 }
 
+static int tcg_fixup_ppc_env(CPUPPCState *env, const ppc_def_t *def)
+{
+    /* TCG doesn't (yet) emulate some groups of instructions that
+     * are implemented on some otherwise supported CPUs (e.g. VSX
+     * and decimal floating point instructions on POWER7).  We
+     * remove unsupported instruction groups from the cpu state's
+     * instruction masks and hope the guest can cope.  For at
+     * least the pseries machine, the unavailability of these
+     * instructions can be advertise to the guest via the device
+     * tree. */
+    if ((env->insns_flags & ~PPC_TCG_INSNS)
+        || (env->insns_flags2 & ~PPC_TCG_INSNS2)) {
+        fprintf(stderr, "Warning: Disabling some instructions which are not "
+                "emulated by TCG (0x%" PRIx64 ", 0x%" PRIx64 ")\n",
+                env->insns_flags & ~PPC_TCG_INSNS,
+                env->insns_flags2 & ~PPC_TCG_INSNS2);
+    }
+    env->insns_flags &= PPC_TCG_INSNS;
+    env->insns_flags2 &= PPC_TCG_INSNS2;
+    return 0;
+}
+
 int cpu_ppc_register_internal (CPUPPCState *env, const ppc_def_t *def)
 {
     env->msr_mask = def->msr_mask;
@@ -9897,25 +9919,22 @@ int cpu_ppc_register_internal (CPUPPCState *env, const ppc_def_t *def)
     env->bus_model = def->bus_model;
     env->insns_flags = def->insns_flags;
     env->insns_flags2 = def->insns_flags2;
-    if (!kvm_enabled()) {
-        /* TCG doesn't (yet) emulate some groups of instructions that
-         * are implemented on some otherwise supported CPUs (e.g. VSX
-         * and decimal floating point instructions on POWER7).  We
-         * remove unsupported instruction groups from the cpu state's
-         * instruction masks and hope the guest can cope.  For at
-         * least the pseries machine, the unavailability of these
-         * instructions can be advertise to the guest via the device
-         * tree.
-         *
-         * FIXME: we should have a similar masking for CPU features
-         * not accessible under KVM, but so far, there aren't any of
-         * those. */
-        env->insns_flags &= PPC_TCG_INSNS;
-        env->insns_flags2 &= PPC_TCG_INSNS2;
-    }
     env->flags = def->flags;
     env->bfd_mach = def->bfd_mach;
     env->check_pow = def->check_pow;
+
+    if (kvm_enabled()) {
+        if (kvm_fixup_ppc_env(env, def) != 0) {
+            fprintf(stderr, "Unable to virtualize selected cpu with KVM\n");
+            exit(1);
+        }
+    } else {
+        if (tcg_fixup_ppc_env(env, def) != 0) {
+            fprintf(stderr, "Unable to emulated selected cpu with TCG\n");
+            exit(1);
+        }
+    }
+
     if (create_ppc_opcodes(env, def) < 0)
         return -1;
     init_ppc_proc(env, def);
-- 
1.7.9.1