target/riscv/kvm.c: add multi-letter extension KVM properties

Let's add KVM user properties for the multi-letter extensions that KVM
currently supports: zicbom, zicboz, zihintpause, zbb, ssaia, sstc,
svinval and svpbmt.

As with MISA extensions, we're using the KVMCPUConfig type to hold
information about the state of each extension. However, multi-letter
extensions have more cases to cover than MISA extensions, so we're
adding an extra 'supported' flag as well. This flag will reflect if a
given extension is supported by KVM, i.e. KVM knows how to handle it.
This is determined during KVM extension discovery in
kvm_riscv_init_multiext_cfg(), where we test for EINVAL errors. Any
other error will cause an abort.

The use of the 'user_set' is similar to what we already do with MISA
extensions: the flag set only if the user is changing the extension
state.

The 'supported' flag will be used later on to make an exception for
users that are disabling multi-letter extensions that are unknown to
KVM.

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Message-Id: <20230706101738.460804-15-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/cpu.c

@@ -1860,6 +1860,14 @@ static void riscv_cpu_add_user_properties(Object *obj)
     riscv_cpu_add_misa_properties(obj);
 
     for (prop = riscv_cpu_extensions; prop && prop->name; prop++) {
+#ifndef CONFIG_USER_ONLY
+        if (kvm_enabled()) {
+            /* Check if KVM created the property already */
+            if (object_property_find(obj, prop->name)) {
+                continue;
+            }
+        }
+#endif
         qdev_property_add_static(dev, prop);
     }
 

target/riscv/kvm.c

@@ -113,6 +113,7 @@ typedef struct KVMCPUConfig {
     target_ulong offset;
     int kvm_reg_id;
     bool user_set;
+    bool supported;
 } KVMCPUConfig;
 
 #define KVM_MISA_CFG(_bit, _reg_id) \
@@ -197,6 +198,81 @@ static void kvm_riscv_update_cpu_misa_ext(RISCVCPU *cpu, CPUState *cs)
     }
 }
 
+#define CPUCFG(_prop) offsetof(struct RISCVCPUConfig, _prop)
+
+#define KVM_EXT_CFG(_name, _prop, _reg_id) \
+    {.name = _name, .offset = CPUCFG(_prop), \
+     .kvm_reg_id = _reg_id}
+
+static KVMCPUConfig kvm_multi_ext_cfgs[] = {
+    KVM_EXT_CFG("zicbom", ext_icbom, KVM_RISCV_ISA_EXT_ZICBOM),
+    KVM_EXT_CFG("zicboz", ext_icboz, KVM_RISCV_ISA_EXT_ZICBOZ),
+    KVM_EXT_CFG("zihintpause", ext_zihintpause, KVM_RISCV_ISA_EXT_ZIHINTPAUSE),
+    KVM_EXT_CFG("zbb", ext_zbb, KVM_RISCV_ISA_EXT_ZBB),
+    KVM_EXT_CFG("ssaia", ext_ssaia, KVM_RISCV_ISA_EXT_SSAIA),
+    KVM_EXT_CFG("sstc", ext_sstc, KVM_RISCV_ISA_EXT_SSTC),
+    KVM_EXT_CFG("svinval", ext_svinval, KVM_RISCV_ISA_EXT_SVINVAL),
+    KVM_EXT_CFG("svpbmt", ext_svpbmt, KVM_RISCV_ISA_EXT_SVPBMT),
+};
+
+static void kvm_cpu_cfg_set(RISCVCPU *cpu, KVMCPUConfig *multi_ext,
+                            uint32_t val)
+{
+    int cpu_cfg_offset = multi_ext->offset;
+    bool *ext_enabled = (void *)&cpu->cfg + cpu_cfg_offset;
+
+    *ext_enabled = val;
+}
+
+static uint32_t kvm_cpu_cfg_get(RISCVCPU *cpu,
+                                KVMCPUConfig *multi_ext)
+{
+    int cpu_cfg_offset = multi_ext->offset;
+    bool *ext_enabled = (void *)&cpu->cfg + cpu_cfg_offset;
+
+    return *ext_enabled;
+}
+
+static void kvm_cpu_set_multi_ext_cfg(Object *obj, Visitor *v,
+                                      const char *name,
+                                      void *opaque, Error **errp)
+{
+    KVMCPUConfig *multi_ext_cfg = opaque;
+    RISCVCPU *cpu = RISCV_CPU(obj);
+    bool value, host_val;
+
+    if (!visit_type_bool(v, name, &value, errp)) {
+        return;
+    }
+
+    host_val = kvm_cpu_cfg_get(cpu, multi_ext_cfg);
+
+    /*
+     * Ignore if the user is setting the same value
+     * as the host.
+     */
+    if (value == host_val) {
+        return;
+    }
+
+    if (!multi_ext_cfg->supported) {
+        /*
+         * Error out if the user is trying to enable an
+         * extension that KVM doesn't support. Ignore
+         * option otherwise.
+         */
+        if (value) {
+            error_setg(errp, "KVM does not support disabling extension %s",
+                       multi_ext_cfg->name);
+        }
+
+        return;
+    }
+
+    multi_ext_cfg->user_set = true;
+    kvm_cpu_cfg_set(cpu, multi_ext_cfg, value);
+}
+
 static void kvm_riscv_add_cpu_user_properties(Object *cpu_obj)
 {
     int i;
@@ -215,6 +291,15 @@ static void kvm_riscv_add_cpu_user_properties(Object *cpu_obj)
         object_property_set_description(cpu_obj, misa_cfg->name,
                                         misa_cfg->description);
     }
+
+    for (i = 0; i < ARRAY_SIZE(kvm_multi_ext_cfgs); i++) {
+        KVMCPUConfig *multi_cfg = &kvm_multi_ext_cfgs[i];
+
+        object_property_add(cpu_obj, multi_cfg->name, "bool",
+                            NULL,
+                            kvm_cpu_set_multi_ext_cfg,
+                            NULL, multi_cfg);
+    }
 }
 
 static int kvm_riscv_get_regs_core(CPUState *cs)
@@ -530,6 +615,39 @@ static void kvm_riscv_init_misa_ext_mask(RISCVCPU *cpu,
     env->misa_ext = env->misa_ext_mask;
 }
 
+static void kvm_riscv_init_multiext_cfg(RISCVCPU *cpu, KVMScratchCPU *kvmcpu)
+{
+    CPURISCVState *env = &cpu->env;
+    uint64_t val;
+    int i, ret;
+
+    for (i = 0; i < ARRAY_SIZE(kvm_multi_ext_cfgs); i++) {
+        KVMCPUConfig *multi_ext_cfg = &kvm_multi_ext_cfgs[i];
+        struct kvm_one_reg reg;
+
+        reg.id = kvm_riscv_reg_id(env, KVM_REG_RISCV_ISA_EXT,
+                                  multi_ext_cfg->kvm_reg_id);
+        reg.addr = (uint64_t)&val;
+        ret = ioctl(kvmcpu->cpufd, KVM_GET_ONE_REG, &reg);
+        if (ret != 0) {
+            if (errno == EINVAL) {
+                /* Silently default to 'false' if KVM does not support it. */
+                multi_ext_cfg->supported = false;
+                val = false;
+            } else {
+                error_report("Unable to read ISA_EXT KVM register %s, "
+                             "error %d", multi_ext_cfg->name, ret);
+                kvm_riscv_destroy_scratch_vcpu(kvmcpu);
+                exit(EXIT_FAILURE);
+            }
+        } else {
+            multi_ext_cfg->supported = true;
+        }
+
+        kvm_cpu_cfg_set(cpu, multi_ext_cfg, val);
+    }
+}
+
 void kvm_riscv_init_user_properties(Object *cpu_obj)
 {
     RISCVCPU *cpu = RISCV_CPU(cpu_obj);
@@ -542,6 +660,7 @@ void kvm_riscv_init_user_properties(Object *cpu_obj)
     kvm_riscv_add_cpu_user_properties(cpu_obj);
     kvm_riscv_init_machine_ids(cpu, &kvmcpu);
     kvm_riscv_init_misa_ext_mask(cpu, &kvmcpu);
+    kvm_riscv_init_multiext_cfg(cpu, &kvmcpu);
 
     kvm_riscv_destroy_scratch_vcpu(&kvmcpu);
 }