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* [PATCH v2] accel/kvm: Specify default IPA size for arm64
@ 2023-07-21  6:24 Akihiko Odaki
  2023-07-21  7:30 ` Philippe Mathieu-Daudé
  0 siblings, 1 reply; 3+ messages in thread
From: Akihiko Odaki @ 2023-07-21  6:24 UTC (permalink / raw)
  Cc: qemu-devel, qemu-arm, kvm, Paolo Bonzini, Peter Maydell,
	Richard Henderson, Akihiko Odaki

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@daynix.com>
---
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(-)

diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
index 115f0cca79..7cc2eb1a8c 100644
--- a/include/sysemu/kvm.h
+++ b/include/sysemu/kvm.h
@@ -347,6 +347,7 @@ bool kvm_device_supported(int vmfd, uint64_t type);
 
 /* Arch specific hooks */
 
+extern const int kvm_arch_default_type;
 extern const KVMCapabilityInfo kvm_arch_required_capabilities[];
 
 void kvm_arch_accel_class_init(ObjectClass *oc);
diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 373d876c05..914ade3ec3 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 = kvm_arch_default_type;
     uint64_t dirty_log_manual_caps;
 
     qemu_mutex_init(&kml_slots_lock);
diff --git a/target/arm/kvm.c b/target/arm/kvm.c
index b4c7654f49..f8203b9915 100644
--- a/target/arm/kvm.c
+++ b/target/arm/kvm.c
@@ -32,6 +32,8 @@
 #include "hw/irq.h"
 #include "qemu/log.h"
 
+const int kvm_arch_default_type = 32;
+
 const KVMCapabilityInfo kvm_arch_required_capabilities[] = {
     KVM_CAP_LAST_INFO
 };
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index ebfaf3d24c..00bccffdfc 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -87,6 +87,8 @@
 
 static void kvm_init_msrs(X86CPU *cpu);
 
+const int kvm_arch_default_type;
+
 const KVMCapabilityInfo kvm_arch_required_capabilities[] = {
     KVM_CAP_INFO(SET_TSS_ADDR),
     KVM_CAP_INFO(EXT_CPUID),
diff --git a/target/mips/kvm.c b/target/mips/kvm.c
index c14e8f550f..754366874e 100644
--- a/target/mips/kvm.c
+++ b/target/mips/kvm.c
@@ -33,6 +33,8 @@
 static int kvm_mips_fpu_cap;
 static int kvm_mips_msa_cap;
 
+const int kvm_arch_default_type;
+
 const KVMCapabilityInfo kvm_arch_required_capabilities[] = {
     KVM_CAP_LAST_INFO
 };
diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c
index a8a935e267..86f8b645a5 100644
--- a/target/ppc/kvm.c
+++ b/target/ppc/kvm.c
@@ -54,6 +54,8 @@
 #define DEBUG_RETURN_GUEST 0
 #define DEBUG_RETURN_GDB   1
 
+const int kvm_arch_default_type;
+
 const KVMCapabilityInfo kvm_arch_required_capabilities[] = {
     KVM_CAP_LAST_INFO
 };
diff --git a/target/riscv/kvm.c b/target/riscv/kvm.c
index 9d8a8982f9..fbe56ec3bb 100644
--- a/target/riscv/kvm.c
+++ b/target/riscv/kvm.c
@@ -764,6 +764,8 @@ void kvm_riscv_init_user_properties(Object *cpu_obj)
     kvm_riscv_destroy_scratch_vcpu(&kvmcpu);
 }
 
+const int kvm_arch_default_type;
+
 const KVMCapabilityInfo kvm_arch_required_capabilities[] = {
     KVM_CAP_LAST_INFO
 };
diff --git a/target/s390x/kvm/kvm.c b/target/s390x/kvm/kvm.c
index a9e5880349..4b9347ffc8 100644
--- a/target/s390x/kvm/kvm.c
+++ b/target/s390x/kvm/kvm.c
@@ -144,6 +144,8 @@ static CPUWatchpoint hw_watchpoint;
 static struct kvm_hw_breakpoint *hw_breakpoints;
 static int nb_hw_breakpoints;
 
+const int kvm_arch_default_type;
+
 const KVMCapabilityInfo kvm_arch_required_capabilities[] = {
     KVM_CAP_LAST_INFO
 };
-- 
2.41.0



^ permalink raw reply related	[flat|nested] 3+ messages in thread
end of thread, other threads:[~2023-07-21 12:30 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
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2023-07-21  6:24 [PATCH v2] accel/kvm: Specify default IPA size for arm64 Akihiko Odaki
2023-07-21  7:30 ` Philippe Mathieu-Daudé
2023-07-21 12:28   ` Peter Maydell

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