[qemu-xen stable-4.19] accel/kvm: Specify default IPA size for arm64

[patchbot@xxxxxxx]

commit f5cb21416e6fc6a3e2d58f4bb557c929ffe01818
Author:     Akihiko Odaki <akihiko.odaki@xxxxxxxxxx>
AuthorDate: Tue Aug 22 17:31:02 2023 +0100
Commit:     Michael Tokarev <mjt@xxxxxxxxxx>
CommitDate: Sun Sep 10 19:39:41 2023 +0300

    accel/kvm: Specify default IPA size for arm64
    
    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.
    
    Cc: qemu-stable@xxxxxxxxxx
    Signed-off-by: Akihiko Odaki <akihiko.odaki@xxxxxxxxxx>
    Message-id: 20230727073134.134102-3-akihiko.odaki@xxxxxxxxxx
    Reviewed-by: Peter Maydell <peter.maydell@xxxxxxxxxx>
    Signed-off-by: Peter Maydell <peter.maydell@xxxxxxxxxx>
    (cherry picked from commit 1ab445af8cd99343f29032b5944023ad7d8edebf)
    Signed-off-by: Michael Tokarev <mjt@xxxxxxxxxx>
---
 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 34bc329b5b..e219f78535 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)
--
generated by git-patchbot for /home/xen/git/qemu-xen.git#stable-4.19