hvf: arm: Implement -cpu host

Now that we have working system register sync, we push more target CPU
properties into the virtual machine. That might be useful in some
situations, but is not the typical case that users want.

So let's add a -cpu host option that allows them to explicitly pass all
CPU capabilities of their host CPU into the guest.

Signed-off-by: Alexander Graf <agraf@csgraf.de>
Acked-by: Roman Bolshakov <r.bolshakov@yadro.com>
Reviewed-by: Sergio Lopez <slp@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20210916155404.86958-7-agraf@csgraf.de
[PMM: drop unnecessary #include line from .h file]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target/arm/cpu.c

@@ -39,6 +39,7 @@
 #include "sysemu/tcg.h"
 #include "sysemu/hw_accel.h"
 #include "kvm_arm.h"
+#include "hvf_arm.h"
 #include "disas/capstone.h"
 #include "fpu/softfloat.h"
 
@@ -1417,8 +1418,8 @@ static void arm_cpu_realizefn(DeviceState *dev, Error **errp)
      * this is the first point where we can report it.
      */
     if (cpu->host_cpu_probe_failed) {
-        if (!kvm_enabled()) {
-            error_setg(errp, "The 'host' CPU type can only be used with KVM");
+        if (!kvm_enabled() && !hvf_enabled()) {
+            error_setg(errp, "The 'host' CPU type can only be used with KVM or HVF");
         } else {
             error_setg(errp, "Failed to retrieve host CPU features");
         }
@@ -2078,15 +2079,19 @@ static void arm_cpu_class_init(ObjectClass *oc, void *data)
 #endif /* CONFIG_TCG */
 }
 
-#ifdef CONFIG_KVM
+#if defined(CONFIG_KVM) || defined(CONFIG_HVF)
 static void arm_host_initfn(Object *obj)
 {
     ARMCPU *cpu = ARM_CPU(obj);
 
+#ifdef CONFIG_KVM
     kvm_arm_set_cpu_features_from_host(cpu);
     if (arm_feature(&cpu->env, ARM_FEATURE_AARCH64)) {
         aarch64_add_sve_properties(obj);
     }
+#else
+    hvf_arm_set_cpu_features_from_host(cpu);
+#endif
     arm_cpu_post_init(obj);
 }
 
@@ -2146,7 +2151,7 @@ static void arm_cpu_register_types(void)
 {
     type_register_static(&arm_cpu_type_info);
 
-#ifdef CONFIG_KVM
+#if defined(CONFIG_KVM) || defined(CONFIG_HVF)
     type_register_static(&host_arm_cpu_type_info);
 #endif
 }

target/arm/cpu.h

@@ -3015,6 +3015,8 @@ bool write_cpustate_to_list(ARMCPU *cpu, bool kvm_sync);
 #define ARM_CPU_TYPE_NAME(name) (name ARM_CPU_TYPE_SUFFIX)
 #define CPU_RESOLVING_TYPE TYPE_ARM_CPU
 
+#define TYPE_ARM_HOST_CPU "host-" TYPE_ARM_CPU
+
 #define cpu_signal_handler cpu_arm_signal_handler
 #define cpu_list arm_cpu_list
 

target/arm/hvf/hvf.c

@@ -17,6 +17,7 @@
 #include "sysemu/hvf.h"
 #include "sysemu/hvf_int.h"
 #include "sysemu/hw_accel.h"
+#include "hvf_arm.h"
 
 #include <mach/mach_time.h>
 
@@ -54,6 +55,16 @@ typedef struct HVFVTimer {
 
 static HVFVTimer vtimer;
 
+typedef struct ARMHostCPUFeatures {
+    ARMISARegisters isar;
+    uint64_t features;
+    uint64_t midr;
+    uint32_t reset_sctlr;
+    const char *dtb_compatible;
+} ARMHostCPUFeatures;
+
+static ARMHostCPUFeatures arm_host_cpu_features;
+
 struct hvf_reg_match {
     int reg;
     uint64_t offset;
@@ -416,6 +427,90 @@ static uint64_t hvf_get_reg(CPUState *cpu, int rt)
     return val;
 }
 
+static bool hvf_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
+{
+    ARMISARegisters host_isar = {};
+    const struct isar_regs {
+        int reg;
+        uint64_t *val;
+    } regs[] = {
+        { HV_SYS_REG_ID_AA64PFR0_EL1, &host_isar.id_aa64pfr0 },
+        { HV_SYS_REG_ID_AA64PFR1_EL1, &host_isar.id_aa64pfr1 },
+        { HV_SYS_REG_ID_AA64DFR0_EL1, &host_isar.id_aa64dfr0 },
+        { HV_SYS_REG_ID_AA64DFR1_EL1, &host_isar.id_aa64dfr1 },
+        { HV_SYS_REG_ID_AA64ISAR0_EL1, &host_isar.id_aa64isar0 },
+        { HV_SYS_REG_ID_AA64ISAR1_EL1, &host_isar.id_aa64isar1 },
+        { HV_SYS_REG_ID_AA64MMFR0_EL1, &host_isar.id_aa64mmfr0 },
+        { HV_SYS_REG_ID_AA64MMFR1_EL1, &host_isar.id_aa64mmfr1 },
+        { HV_SYS_REG_ID_AA64MMFR2_EL1, &host_isar.id_aa64mmfr2 },
+    };
+    hv_vcpu_t fd;
+    hv_return_t r = HV_SUCCESS;
+    hv_vcpu_exit_t *exit;
+    int i;
+
+    ahcf->dtb_compatible = "arm,arm-v8";
+    ahcf->features = (1ULL << ARM_FEATURE_V8) |
+                     (1ULL << ARM_FEATURE_NEON) |
+                     (1ULL << ARM_FEATURE_AARCH64) |
+                     (1ULL << ARM_FEATURE_PMU) |
+                     (1ULL << ARM_FEATURE_GENERIC_TIMER);
+
+    /* We set up a small vcpu to extract host registers */
+
+    if (hv_vcpu_create(&fd, &exit, NULL) != HV_SUCCESS) {
+        return false;
+    }
+
+    for (i = 0; i < ARRAY_SIZE(regs); i++) {
+        r |= hv_vcpu_get_sys_reg(fd, regs[i].reg, regs[i].val);
+    }
+    r |= hv_vcpu_get_sys_reg(fd, HV_SYS_REG_MIDR_EL1, &ahcf->midr);
+    r |= hv_vcpu_destroy(fd);
+
+    ahcf->isar = host_isar;
+
+    /*
+     * A scratch vCPU returns SCTLR 0, so let's fill our default with the M1
+     * boot SCTLR from https://github.com/AsahiLinux/m1n1/issues/97
+     */
+    ahcf->reset_sctlr = 0x30100180;
+    /*
+     * SPAN is disabled by default when SCTLR.SPAN=1. To improve compatibility,
+     * let's disable it on boot and then allow guest software to turn it on by
+     * setting it to 0.
+     */
+    ahcf->reset_sctlr |= 0x00800000;
+
+    /* Make sure we don't advertise AArch32 support for EL0/EL1 */
+    if ((host_isar.id_aa64pfr0 & 0xff) != 0x11) {
+        return false;
+    }
+
+    return r == HV_SUCCESS;
+}
+
+void hvf_arm_set_cpu_features_from_host(ARMCPU *cpu)
+{
+    if (!arm_host_cpu_features.dtb_compatible) {
+        if (!hvf_enabled() ||
+            !hvf_arm_get_host_cpu_features(&arm_host_cpu_features)) {
+            /*
+             * We can't report this error yet, so flag that we need to
+             * in arm_cpu_realizefn().
+             */
+            cpu->host_cpu_probe_failed = true;
+            return;
+        }
+    }
+
+    cpu->dtb_compatible = arm_host_cpu_features.dtb_compatible;
+    cpu->isar = arm_host_cpu_features.isar;
+    cpu->env.features = arm_host_cpu_features.features;
+    cpu->midr = arm_host_cpu_features.midr;
+    cpu->reset_sctlr = arm_host_cpu_features.reset_sctlr;
+}
+
 void hvf_arch_vcpu_destroy(CPUState *cpu)
 {
 }

target/arm/hvf_arm.h

@@ -0,0 +1,18 @@
+/*
+ * QEMU Hypervisor.framework (HVF) support -- ARM specifics
+ *
+ * Copyright (c) 2021 Alexander Graf
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#ifndef QEMU_HVF_ARM_H
+#define QEMU_HVF_ARM_H
+
+#include "cpu.h"
+
+void hvf_arm_set_cpu_features_from_host(struct ARMCPU *cpu);
+
+#endif

target/arm/kvm_arm.h

@@ -214,8 +214,6 @@ bool kvm_arm_create_scratch_host_vcpu(const uint32_t *cpus_to_try,
  */
 void kvm_arm_destroy_scratch_host_vcpu(int *fdarray);
 
-#define TYPE_ARM_HOST_CPU "host-" TYPE_ARM_CPU
-
 /**
  * ARMHostCPUFeatures: information about the host CPU (identified
  * by asking the host kernel)