Hi Akihiko,
On 21/7/23 08:24, Akihiko Odaki wrote:
libvirt uses "none" machine type to test KVM availability. Before this
change, QEMU used to pass 0 as machine type when calling KVM_CREATE_VM.
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, such KVM_CREATE_VM will fail, and libvirt
incorrectly thinks KVM is not available. This actually happened on M2
MacBook Air.
Fix this by specifying 32 for IPA_Bits as any arm64 system should
support the value according to the documentation.
Signed-off-by: Akihiko Odaki <akihiko.odaki@xxxxxxxxxx>
---
V1 -> V2: Introduced an arch hook
include/sysemu/kvm.h | 1 +
accel/kvm/kvm-all.c | 2 +-
target/arm/kvm.c | 2 ++
target/i386/kvm/kvm.c | 2 ++
target/mips/kvm.c | 2 ++
target/ppc/kvm.c | 2 ++
target/riscv/kvm.c | 2 ++
target/s390x/kvm/kvm.c | 2 ++
8 files changed, 14 insertions(+), 1 deletion(-)
My understanding of Peter's suggestion would be smth like:
-- >8 --
diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
index 115f0cca79..c0af15eb6c 100644
--- a/include/sysemu/kvm.h
+++ b/include/sysemu/kvm.h
@@ -201,10 +201,15 @@ typedef struct KVMCapabilityInfo {
struct KVMState;
+struct KVMClass {
+ AccelClass parent_class;
+
+ int default_vm_type;
+};
+
#define TYPE_KVM_ACCEL ACCEL_CLASS_NAME("kvm")
typedef struct KVMState KVMState;
-DECLARE_INSTANCE_CHECKER(KVMState, KVM_STATE,
- TYPE_KVM_ACCEL)
+OBJECT_DECLARE_TYPE(KVMState, KVMClass, KVM_ACCEL)
extern KVMState *kvm_state;
typedef struct Notifier Notifier;
diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 373d876c05..fdd424e1a5 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -2458,12 +2458,13 @@ 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);
s = KVM_STATE(ms->accelerator);
+ type = KVM_GET_CLASS(s)->default_vm_type;
/*
* On systems where the kernel can support different base page
diff --git a/target/arm/kvm.c b/target/arm/kvm.c
index b4c7654f49..5c13594fdf 100644
--- a/target/arm/kvm.c
+++ b/target/arm/kvm.c
@@ -1064,4 +1064,8 @@ bool kvm_arch_cpu_check_are_resettable(void)
void kvm_arch_accel_class_init(ObjectClass *oc)
{
+ KVMClass *kc = KVM_CLASS(oc);
+
+ /* Host_IPA_Limit ... */
+ kc->default_vm_type = 32;
}
---
