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Scott Woodagraf
Scott Wood
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agraf
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kvm: add device control API
Currently, devices that are emulated inside KVM are configured in a hardcoded manner based on an assumption that any given architecture only has one way to do it. If there's any need to access device state, it is done through inflexible one-purpose-only IOCTLs (e.g. KVM_GET/SET_LAPIC). Defining new IOCTLs for every little thing is cumbersome and depletes a limited numberspace. This API provides a mechanism to instantiate a device of a certain type, returning an ID that can be used to set/get attributes of the device. Attributes may include configuration parameters (e.g. register base address), device state, operational commands, etc. It is similar to the ONE_REG API, except that it acts on devices rather than vcpus. Both device types and individual attributes can be tested without having to create the device or get/set the attribute, without the need for separately managing enumerated capabilities. Signed-off-by: Scott Wood <scottwood@freescale.com> Signed-off-by: Alexander Graf <agraf@suse.de>
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‎Documentation/virtual/kvm/api.txt

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@@ -2189,6 +2189,76 @@ header; first `n_valid' valid entries with contents from the data
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written, then `n_invalid' invalid entries, invalidating any previously
21902190
valid entries found.
21912191

2192+
4.79 KVM_CREATE_DEVICE
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2194+
Capability: KVM_CAP_DEVICE_CTRL
2195+
Type: vm ioctl
2196+
Parameters: struct kvm_create_device (in/out)
2197+
Returns: 0 on success, -1 on error
2198+
Errors:
2199+
ENODEV: The device type is unknown or unsupported
2200+
EEXIST: Device already created, and this type of device may not
2201+
be instantiated multiple times
2202+
2203+
Other error conditions may be defined by individual device types or
2204+
have their standard meanings.
2205+
2206+
Creates an emulated device in the kernel. The file descriptor returned
2207+
in fd can be used with KVM_SET/GET/HAS_DEVICE_ATTR.
2208+
2209+
If the KVM_CREATE_DEVICE_TEST flag is set, only test whether the
2210+
device type is supported (not necessarily whether it can be created
2211+
in the current vm).
2212+
2213+
Individual devices should not define flags. Attributes should be used
2214+
for specifying any behavior that is not implied by the device type
2215+
number.
2216+
2217+
struct kvm_create_device {
2218+
__u32 type; /* in: KVM_DEV_TYPE_xxx */
2219+
__u32 fd; /* out: device handle */
2220+
__u32 flags; /* in: KVM_CREATE_DEVICE_xxx */
2221+
};
2222+
2223+
4.80 KVM_SET_DEVICE_ATTR/KVM_GET_DEVICE_ATTR
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2225+
Capability: KVM_CAP_DEVICE_CTRL
2226+
Type: device ioctl
2227+
Parameters: struct kvm_device_attr
2228+
Returns: 0 on success, -1 on error
2229+
Errors:
2230+
ENXIO: The group or attribute is unknown/unsupported for this device
2231+
EPERM: The attribute cannot (currently) be accessed this way
2232+
(e.g. read-only attribute, or attribute that only makes
2233+
sense when the device is in a different state)
2234+
2235+
Other error conditions may be defined by individual device types.
2236+
2237+
Gets/sets a specified piece of device configuration and/or state. The
2238+
semantics are device-specific. See individual device documentation in
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the "devices" directory. As with ONE_REG, the size of the data
2240+
transferred is defined by the particular attribute.
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struct kvm_device_attr {
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__u32 flags; /* no flags currently defined */
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__u32 group; /* device-defined */
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__u64 attr; /* group-defined */
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__u64 addr; /* userspace address of attr data */
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};
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4.81 KVM_HAS_DEVICE_ATTR
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2251+
Capability: KVM_CAP_DEVICE_CTRL
2252+
Type: device ioctl
2253+
Parameters: struct kvm_device_attr
2254+
Returns: 0 on success, -1 on error
2255+
Errors:
2256+
ENXIO: The group or attribute is unknown/unsupported for this device
2257+
2258+
Tests whether a device supports a particular attribute. A successful
2259+
return indicates the attribute is implemented. It does not necessarily
2260+
indicate that the attribute can be read or written in the device's
2261+
current state. "addr" is ignored.
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4.77 KVM_ARM_VCPU_INIT
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‎Documentation/virtual/kvm/devices/README

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@@ -0,0 +1 @@
1+
This directory contains specific device bindings for KVM_CAP_DEVICE_CTRL.

‎include/linux/kvm_host.h

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@@ -1064,6 +1064,41 @@ static inline bool kvm_check_request(int req, struct kvm_vcpu *vcpu)
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10651065
extern bool kvm_rebooting;
10661066

1067+
struct kvm_device_ops;
1068+
1069+
struct kvm_device {
1070+
struct kvm_device_ops *ops;
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struct kvm *kvm;
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atomic_t users;
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void *private;
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};
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/* create, destroy, and name are mandatory */
1077+
struct kvm_device_ops {
1078+
const char *name;
1079+
int (*create)(struct kvm_device *dev, u32 type);
1080+
1081+
/*
1082+
* Destroy is responsible for freeing dev.
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*
1084+
* Destroy may be called before or after destructors are called
1085+
* on emulated I/O regions, depending on whether a reference is
1086+
* held by a vcpu or other kvm component that gets destroyed
1087+
* after the emulated I/O.
1088+
*/
1089+
void (*destroy)(struct kvm_device *dev);
1090+
1091+
int (*set_attr)(struct kvm_device *dev, struct kvm_device_attr *attr);
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int (*get_attr)(struct kvm_device *dev, struct kvm_device_attr *attr);
1093+
int (*has_attr)(struct kvm_device *dev, struct kvm_device_attr *attr);
1094+
long (*ioctl)(struct kvm_device *dev, unsigned int ioctl,
1095+
unsigned long arg);
1096+
};
1097+
1098+
void kvm_device_get(struct kvm_device *dev);
1099+
void kvm_device_put(struct kvm_device *dev);
1100+
struct kvm_device *kvm_device_from_filp(struct file *filp);
1101+
10671102
#ifdef CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT
10681103

10691104
static inline void kvm_vcpu_set_in_spin_loop(struct kvm_vcpu *vcpu, bool val)

‎include/uapi/linux/kvm.h

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Original file line numberDiff line numberDiff line change
@@ -666,6 +666,7 @@ struct kvm_ppc_smmu_info {
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#define KVM_CAP_PPC_EPR 86
667667
#define KVM_CAP_ARM_PSCI 87
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#define KVM_CAP_ARM_SET_DEVICE_ADDR 88
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#define KVM_CAP_DEVICE_CTRL 89
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670671
#ifdef KVM_CAP_IRQ_ROUTING
671672

@@ -818,6 +819,24 @@ struct kvm_arm_device_addr {
818819
__u64 addr;
819820
};
820821

822+
/*
823+
* Device control API, available with KVM_CAP_DEVICE_CTRL
824+
*/
825+
#define KVM_CREATE_DEVICE_TEST 1
826+
827+
struct kvm_create_device {
828+
__u32 type; /* in: KVM_DEV_TYPE_xxx */
829+
__u32 fd; /* out: device handle */
830+
__u32 flags; /* in: KVM_CREATE_DEVICE_xxx */
831+
};
832+
833+
struct kvm_device_attr {
834+
__u32 flags; /* no flags currently defined */
835+
__u32 group; /* device-defined */
836+
__u64 attr; /* group-defined */
837+
__u64 addr; /* userspace address of attr data */
838+
};
839+
821840
/*
822841
* ioctls for VM fds
823842
*/
@@ -906,6 +925,14 @@ struct kvm_s390_ucas_mapping {
906925
/* Available with KVM_CAP_ARM_SET_DEVICE_ADDR */
907926
#define KVM_ARM_SET_DEVICE_ADDR _IOW(KVMIO, 0xab, struct kvm_arm_device_addr)
908927

928+
/* ioctl for vm fd */
929+
#define KVM_CREATE_DEVICE _IOWR(KVMIO, 0xe0, struct kvm_create_device)
930+
931+
/* ioctls for fds returned by KVM_CREATE_DEVICE */
932+
#define KVM_SET_DEVICE_ATTR _IOW(KVMIO, 0xe1, struct kvm_device_attr)
933+
#define KVM_GET_DEVICE_ATTR _IOW(KVMIO, 0xe2, struct kvm_device_attr)
934+
#define KVM_HAS_DEVICE_ATTR _IOW(KVMIO, 0xe3, struct kvm_device_attr)
935+
909936
/*
910937
* ioctls for vcpu fds
911938
*/

‎virt/kvm/kvm_main.c

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Original file line numberDiff line numberDiff line change
@@ -2159,6 +2159,117 @@ static long kvm_vcpu_compat_ioctl(struct file *filp,
21592159
}
21602160
#endif
21612161

2162+
static int kvm_device_ioctl_attr(struct kvm_device *dev,
2163+
int (*accessor)(struct kvm_device *dev,
2164+
struct kvm_device_attr *attr),
2165+
unsigned long arg)
2166+
{
2167+
struct kvm_device_attr attr;
2168+
2169+
if (!accessor)
2170+
return -EPERM;
2171+
2172+
if (copy_from_user(&attr, (void __user *)arg, sizeof(attr)))
2173+
return -EFAULT;
2174+
2175+
return accessor(dev, &attr);
2176+
}
2177+
2178+
static long kvm_device_ioctl(struct file *filp, unsigned int ioctl,
2179+
unsigned long arg)
2180+
{
2181+
struct kvm_device *dev = filp->private_data;
2182+
2183+
switch (ioctl) {
2184+
case KVM_SET_DEVICE_ATTR:
2185+
return kvm_device_ioctl_attr(dev, dev->ops->set_attr, arg);
2186+
case KVM_GET_DEVICE_ATTR:
2187+
return kvm_device_ioctl_attr(dev, dev->ops->get_attr, arg);
2188+
case KVM_HAS_DEVICE_ATTR:
2189+
return kvm_device_ioctl_attr(dev, dev->ops->has_attr, arg);
2190+
default:
2191+
if (dev->ops->ioctl)
2192+
return dev->ops->ioctl(dev, ioctl, arg);
2193+
2194+
return -ENOTTY;
2195+
}
2196+
}
2197+
2198+
void kvm_device_get(struct kvm_device *dev)
2199+
{
2200+
atomic_inc(&dev->users);
2201+
}
2202+
2203+
void kvm_device_put(struct kvm_device *dev)
2204+
{
2205+
if (atomic_dec_and_test(&dev->users))
2206+
dev->ops->destroy(dev);
2207+
}
2208+
2209+
static int kvm_device_release(struct inode *inode, struct file *filp)
2210+
{
2211+
struct kvm_device *dev = filp->private_data;
2212+
struct kvm *kvm = dev->kvm;
2213+
2214+
kvm_device_put(dev);
2215+
kvm_put_kvm(kvm);
2216+
return 0;
2217+
}
2218+
2219+
static const struct file_operations kvm_device_fops = {
2220+
.unlocked_ioctl = kvm_device_ioctl,
2221+
.release = kvm_device_release,
2222+
};
2223+
2224+
struct kvm_device *kvm_device_from_filp(struct file *filp)
2225+
{
2226+
if (filp->f_op != &kvm_device_fops)
2227+
return NULL;
2228+
2229+
return filp->private_data;
2230+
}
2231+
2232+
static int kvm_ioctl_create_device(struct kvm *kvm,
2233+
struct kvm_create_device *cd)
2234+
{
2235+
struct kvm_device_ops *ops = NULL;
2236+
struct kvm_device *dev;
2237+
bool test = cd->flags & KVM_CREATE_DEVICE_TEST;
2238+
int ret;
2239+
2240+
switch (cd->type) {
2241+
default:
2242+
return -ENODEV;
2243+
}
2244+
2245+
if (test)
2246+
return 0;
2247+
2248+
dev = kzalloc(sizeof(*dev), GFP_KERNEL);
2249+
if (!dev)
2250+
return -ENOMEM;
2251+
2252+
dev->ops = ops;
2253+
dev->kvm = kvm;
2254+
atomic_set(&dev->users, 1);
2255+
2256+
ret = ops->create(dev, cd->type);
2257+
if (ret < 0) {
2258+
kfree(dev);
2259+
return ret;
2260+
}
2261+
2262+
ret = anon_inode_getfd(ops->name, &kvm_device_fops, dev, O_RDWR);
2263+
if (ret < 0) {
2264+
ops->destroy(dev);
2265+
return ret;
2266+
}
2267+
2268+
kvm_get_kvm(kvm);
2269+
cd->fd = ret;
2270+
return 0;
2271+
}
2272+
21622273
static long kvm_vm_ioctl(struct file *filp,
21632274
unsigned int ioctl, unsigned long arg)
21642275
{
@@ -2304,6 +2415,24 @@ static long kvm_vm_ioctl(struct file *filp,
23042415
break;
23052416
}
23062417
#endif /* CONFIG_HAVE_KVM_IRQ_ROUTING */
2418+
case KVM_CREATE_DEVICE: {
2419+
struct kvm_create_device cd;
2420+
2421+
r = -EFAULT;
2422+
if (copy_from_user(&cd, argp, sizeof(cd)))
2423+
goto out;
2424+
2425+
r = kvm_ioctl_create_device(kvm, &cd);
2426+
if (r)
2427+
goto out;
2428+
2429+
r = -EFAULT;
2430+
if (copy_to_user(argp, &cd, sizeof(cd)))
2431+
goto out;
2432+
2433+
r = 0;
2434+
break;
2435+
}
23072436
default:
23082437
r = kvm_arch_vm_ioctl(filp, ioctl, arg);
23092438
if (r == -ENOTTY)

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