KVM: introduce new vendor op for KVM_GET_DEVICE_ATTR

Allow vendor modules to provide their own attributes on /dev/kvm.
To avoid proliferation of vendor ops, implement KVM_HAS_DEVICE_ATTR
and KVM_GET_DEVICE_ATTR in terms of the same function.  You're not
supposed to use KVM_GET_DEVICE_ATTR to do complicated computations,
especially on /dev/kvm.

Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Isaku Yamahata <isaku.yamahata@intel.com>
Message-ID: <20240404121327.3107131-5-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
index 110d7f29ca9a20329ef3346588f06efbf3fbd113..5187fcf4b610b99f50a792092da6b354b3c3a83e 100644 (file)
--- a/arch/x86/include/asm/kvm-x86-ops.h
+++ b/arch/x86/include/asm/kvm-x86-ops.h
@@ -121,6 +121,7 @@ KVM_X86_OP(enter_smm)
 KVM_X86_OP(leave_smm)
 KVM_X86_OP(enable_smi_window)
 #endif
+KVM_X86_OP_OPTIONAL(dev_get_attr)
 KVM_X86_OP_OPTIONAL(mem_enc_ioctl)
 KVM_X86_OP_OPTIONAL(mem_enc_register_region)
 KVM_X86_OP_OPTIONAL(mem_enc_unregister_region)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 16e07a2eee195d48e29536dc69c5d6e975c99d7f..04c430eb25cf1d32ee733ff2e0a9fab8b2dd9fbb 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1778,6 +1778,7 @@ struct kvm_x86_ops {
        void (*enable_smi_window)(struct kvm_vcpu *vcpu);
 #endif
 
+       int (*dev_get_attr)(u32 group, u64 attr, u64 *val);
        int (*mem_enc_ioctl)(struct kvm *kvm, void __user *argp);
        int (*mem_enc_register_region)(struct kvm *kvm, struct kvm_enc_region *argp);
        int (*mem_enc_unregister_region)(struct kvm *kvm, struct kvm_enc_region *argp);

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3d2029402513c59dc94ba16b26c90a40fe492d83..3934e768273461888399f9e5cacf4886c1a52d47 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4842,34 +4842,44 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
        return r;
 }
 
-static int kvm_x86_dev_get_attr(struct kvm_device_attr *attr)
+static int __kvm_x86_dev_get_attr(struct kvm_device_attr *attr, u64 *val)
 {
-       u64 __user *uaddr = u64_to_user_ptr(attr->addr);
-
-       if (attr->group)
+       if (attr->group) {
+               if (kvm_x86_ops.dev_get_attr)
+                       return static_call(kvm_x86_dev_get_attr)(attr->group, attr->attr, val);
                return -ENXIO;
+       }
 
        switch (attr->attr) {
        case KVM_X86_XCOMP_GUEST_SUPP:
-               if (put_user(kvm_caps.supported_xcr0, uaddr))
-                       return -EFAULT;
+               *val = kvm_caps.supported_xcr0;
                return 0;
        default:
                return -ENXIO;
        }
 }
 
+static int kvm_x86_dev_get_attr(struct kvm_device_attr *attr)
+{
+       u64 __user *uaddr = u64_to_user_ptr(attr->addr);
+       int r;
+       u64 val;
+
+       r = __kvm_x86_dev_get_attr(attr, &val);
+       if (r < 0)
+               return r;
+
+       if (put_user(val, uaddr))
+               return -EFAULT;
+
+       return 0;
+}
+
 static int kvm_x86_dev_has_attr(struct kvm_device_attr *attr)
 {
-       if (attr->group)
-               return -ENXIO;
+       u64 val;
 
-       switch (attr->attr) {
-       case KVM_X86_XCOMP_GUEST_SUPP:
-               return 0;
-       default:
-               return -ENXIO;
-       }
+       return __kvm_x86_dev_get_attr(attr, &val);
 }
 
 long kvm_arch_dev_ioctl(struct file *filp,