[PATCH v3 0/2] accel/kvm: Specify default IPA size for arm64

[PATCH v3 0/2] accel/kvm: Specify default IPA size for arm64

[Akihiko Odaki]

Some Arm systems such as Apple Silicon Macs have IPA size smaller than the
default used by KVM. Introduce our own default IPA size that fits on such a
system.

V2 -> V3: Changed to use the maximum IPA size as the default.
V1 -> V2: Introduced an arch hook

Akihiko Odaki (2):
  kvm: Introduce kvm_arch_get_default_type hook
  accel/kvm: Specify default IPA size for arm64

 include/sysemu/kvm.h     | 2 ++
 target/mips/kvm_mips.h   | 9 ---------
 accel/kvm/kvm-all.c      | 4 +++-
 hw/mips/loongson3_virt.c | 1 -
 target/arm/kvm.c         | 7 +++++++
 target/i386/kvm/kvm.c    | 5 +++++
 target/mips/kvm.c        | 2 +-
 target/ppc/kvm.c         | 5 +++++
 target/riscv/kvm.c       | 5 +++++
 target/s390x/kvm/kvm.c   | 5 +++++
 10 files changed, 33 insertions(+), 12 deletions(-)

-- 
2.41.0

[PATCH v3 1/2] kvm: Introduce kvm_arch_get_default_type hook

[Akihiko Odaki]

kvm_arch_get_default_type() returns the default KVM type. This hook is
particularly useful to derive a KVM type that is valid for "none"
machine model, which is used by libvirt to probe the availability of
KVM.

For MIPS, the existing mips_kvm_type() is reused. This function ensures
the availability of VZ which is mandatory to use KVM on the current
QEMU.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
---
 include/sysemu/kvm.h     | 2 ++
 target/mips/kvm_mips.h   | 9 ---------
 accel/kvm/kvm-all.c      | 4 +++-
 hw/mips/loongson3_virt.c | 1 -
 target/arm/kvm.c         | 5 +++++
 target/i386/kvm/kvm.c    | 5 +++++
 target/mips/kvm.c        | 2 +-
 target/ppc/kvm.c         | 5 +++++
 target/riscv/kvm.c       | 5 +++++
 target/s390x/kvm/kvm.c   | 5 +++++
 10 files changed, 31 insertions(+), 12 deletions(-)

diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
index 115f0cca79..ccaf55caf7 100644
--- a/include/sysemu/kvm.h
+++ b/include/sysemu/kvm.h
@@ -369,6 +369,8 @@ int kvm_arch_get_registers(CPUState *cpu);
 
 int kvm_arch_put_registers(CPUState *cpu, int level);
 
+int kvm_arch_get_default_type(MachineState *ms);
+
 int kvm_arch_init(MachineState *ms, KVMState *s);
 
 int kvm_arch_init_vcpu(CPUState *cpu);
diff --git a/target/mips/kvm_mips.h b/target/mips/kvm_mips.h
index 171d53dbe1..c711269d0a 100644
--- a/target/mips/kvm_mips.h
+++ b/target/mips/kvm_mips.h
@@ -25,13 +25,4 @@ void kvm_mips_reset_vcpu(MIPSCPU *cpu);
 int kvm_mips_set_interrupt(MIPSCPU *cpu, int irq, int level);
 int kvm_mips_set_ipi_interrupt(MIPSCPU *cpu, int irq, int level);
 
-#ifdef CONFIG_KVM
-int mips_kvm_type(MachineState *machine, const char *vm_type);
-#else
-static inline int mips_kvm_type(MachineState *machine, const char *vm_type)
-{
-    return 0;
-}
-#endif
-
 #endif /* KVM_MIPS_H */
diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 373d876c05..d591b5079c 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -2458,7 +2458,7 @@ static int kvm_init(MachineState *ms)
     KVMState *s;
     const KVMCapabilityInfo *missing_cap;
     int ret;
-    int type = 0;
+    int type;
     uint64_t dirty_log_manual_caps;
 
     qemu_mutex_init(&kml_slots_lock);
@@ -2523,6 +2523,8 @@ static int kvm_init(MachineState *ms)
         type = mc->kvm_type(ms, kvm_type);
     } else if (mc->kvm_type) {
         type = mc->kvm_type(ms, NULL);
+    } else {
+        type = kvm_arch_get_default_type(ms);
     }
 
     do {
diff --git a/hw/mips/loongson3_virt.c b/hw/mips/loongson3_virt.c
index 4018b8c1d3..bf28f7ec43 100644
--- a/hw/mips/loongson3_virt.c
+++ b/hw/mips/loongson3_virt.c
@@ -612,7 +612,6 @@ static void loongson3v_machine_class_init(ObjectClass *oc, void *data)
     mc->max_cpus = LOONGSON_MAX_VCPUS;
     mc->default_ram_id = "loongson3.highram";
     mc->default_ram_size = 1600 * MiB;
-    mc->kvm_type = mips_kvm_type;
     mc->minimum_page_bits = 14;
     mc->default_nic = "virtio-net-pci";
 }
diff --git a/target/arm/kvm.c b/target/arm/kvm.c
index b4c7654f49..40f577bfd5 100644
--- a/target/arm/kvm.c
+++ b/target/arm/kvm.c
@@ -247,6 +247,11 @@ int kvm_arm_get_max_vm_ipa_size(MachineState *ms, bool *fixed_ipa)
     return ret > 0 ? ret : 40;
 }
 
+int kvm_arch_get_default_type(MachineState *ms)
+{
+    return 0;
+}
+
 int kvm_arch_init(MachineState *ms, KVMState *s)
 {
     int ret = 0;
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index ebfaf3d24c..b45ce20fd8 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -2556,6 +2556,11 @@ static void register_smram_listener(Notifier *n, void *unused)
                                  &smram_address_space, 1, "kvm-smram");
 }
 
+int kvm_arch_get_default_type(MachineState *ms)
+{
+    return 0;
+}
+
 int kvm_arch_init(MachineState *ms, KVMState *s)
 {
     uint64_t identity_base = 0xfffbc000;
diff --git a/target/mips/kvm.c b/target/mips/kvm.c
index c14e8f550f..e98aad01bd 100644
--- a/target/mips/kvm.c
+++ b/target/mips/kvm.c
@@ -1266,7 +1266,7 @@ int kvm_arch_msi_data_to_gsi(uint32_t data)
     abort();
 }
 
-int mips_kvm_type(MachineState *machine, const char *vm_type)
+int kvm_arch_get_default_type(MachineState *machine)
 {
 #if defined(KVM_CAP_MIPS_VZ)
     int r;
diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c
index a8a935e267..dc1182cd37 100644
--- a/target/ppc/kvm.c
+++ b/target/ppc/kvm.c
@@ -108,6 +108,11 @@ static int kvm_ppc_register_host_cpu_type(void);
 static void kvmppc_get_cpu_characteristics(KVMState *s);
 static int kvmppc_get_dec_bits(void);
 
+int kvm_arch_get_default_type(MachineState *ms)
+{
+    return 0;
+}
+
 int kvm_arch_init(MachineState *ms, KVMState *s)
 {
     cap_interrupt_unset = kvm_check_extension(s, KVM_CAP_PPC_UNSET_IRQ);
diff --git a/target/riscv/kvm.c b/target/riscv/kvm.c
index 9d8a8982f9..4266dce092 100644
--- a/target/riscv/kvm.c
+++ b/target/riscv/kvm.c
@@ -907,6 +907,11 @@ int kvm_arch_add_msi_route_post(struct kvm_irq_routing_entry *route,
     return 0;
 }
 
+int kvm_arch_get_default_type(MachineState *ms)
+{
+    return 0;
+}
+
 int kvm_arch_init(MachineState *ms, KVMState *s)
 {
     return 0;
diff --git a/target/s390x/kvm/kvm.c b/target/s390x/kvm/kvm.c
index a9e5880349..9117fab6e8 100644
--- a/target/s390x/kvm/kvm.c
+++ b/target/s390x/kvm/kvm.c
@@ -340,6 +340,11 @@ static void ccw_machine_class_foreach(ObjectClass *oc, void *opaque)
     mc->default_cpu_type = S390_CPU_TYPE_NAME("host");
 }
 
+int kvm_arch_get_default_type(MachineState *ms)
+{
+    return 0;
+}
+
 int kvm_arch_init(MachineState *ms, KVMState *s)
 {
     object_class_foreach(ccw_machine_class_foreach, TYPE_S390_CCW_MACHINE,
-- 
2.41.0

Re: [PATCH v3 1/2] kvm: Introduce kvm_arch_get_default_type hook

[Philippe Mathieu-Daudé]

On 22/7/23 08:22, Akihiko Odaki wrote:
> kvm_arch_get_default_type() returns the default KVM type. This hook is
> particularly useful to derive a KVM type that is valid for "none"
> machine model, which is used by libvirt to probe the availability of
> KVM.
> 
> For MIPS, the existing mips_kvm_type() is reused. This function ensures
> the availability of VZ which is mandatory to use KVM on the current
> QEMU.

Pre-existing: mips_kvm_type() returns -1. Should we check for
'type' in kvm_init() before calling kvm_ioctl()?

> Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
> ---
>   include/sysemu/kvm.h     | 2 ++
>   target/mips/kvm_mips.h   | 9 ---------
>   accel/kvm/kvm-all.c      | 4 +++-
>   hw/mips/loongson3_virt.c | 1 -
>   target/arm/kvm.c         | 5 +++++
>   target/i386/kvm/kvm.c    | 5 +++++
>   target/mips/kvm.c        | 2 +-
>   target/ppc/kvm.c         | 5 +++++
>   target/riscv/kvm.c       | 5 +++++
>   target/s390x/kvm/kvm.c   | 5 +++++
>   10 files changed, 31 insertions(+), 12 deletions(-)

[PATCH v3 2/2] accel/kvm: Specify default IPA size for arm64

[Akihiko Odaki]

Before this change, the default KVM type, which is used for non-virt
machine models, was 0.

The kernel documentation says:
> On arm64, the physical address size for a VM (IPA Size limit) is
> limited to 40bits by default. The limit can be configured if the host
> supports the extension KVM_CAP_ARM_VM_IPA_SIZE. When supported, use
> KVM_VM_TYPE_ARM_IPA_SIZE(IPA_Bits) to set the size in the machine type
> identifier, where IPA_Bits is the maximum width of any physical
> address used by the VM. The IPA_Bits is encoded in bits[7-0] of the
> machine type identifier.
>
> e.g, to configure a guest to use 48bit physical address size::
>
>     vm_fd = ioctl(dev_fd, KVM_CREATE_VM, KVM_VM_TYPE_ARM_IPA_SIZE(48));
>
> The requested size (IPA_Bits) must be:
>
>  ==   =========================================================
>   0   Implies default size, 40bits (for backward compatibility)
>   N   Implies N bits, where N is a positive integer such that,
>       32 <= N <= Host_IPA_Limit
>  ==   =========================================================

> Host_IPA_Limit is the maximum possible value for IPA_Bits on the host
> and is dependent on the CPU capability and the kernel configuration.
> The limit can be retrieved using KVM_CAP_ARM_VM_IPA_SIZE of the
> KVM_CHECK_EXTENSION ioctl() at run-time.
>
> Creation of the VM will fail if the requested IPA size (whether it is
> implicit or explicit) is unsupported on the host.
https://docs.kernel.org/virt/kvm/api.html#kvm-create-vm

So if Host_IPA_Limit < 40, specifying 0 as the type will fail. This
actually confused libvirt, which uses "none" machine model to probe the
KVM availability, on M2 MacBook Air.

Fix this by using Host_IPA_Limit as the default type when
KVM_CAP_ARM_VM_IPA_SIZE is available.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
---
 target/arm/kvm.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/target/arm/kvm.c b/target/arm/kvm.c
index 40f577bfd5..23aeb09949 100644
--- a/target/arm/kvm.c
+++ b/target/arm/kvm.c
@@ -249,7 +249,9 @@ int kvm_arm_get_max_vm_ipa_size(MachineState *ms, bool *fixed_ipa)
 
 int kvm_arch_get_default_type(MachineState *ms)
 {
-    return 0;
+    bool fixed_ipa;
+    int size = kvm_arm_get_max_vm_ipa_size(ms, &fixed_ipa);
+    return fixed_ipa ? 0 : size;
 }
 
 int kvm_arch_init(MachineState *ms, KVMState *s)
-- 
2.41.0