The guest can use KVM_USER_EXIT instead of a signal-based exiting to
userspace. Availability depends on KVM_CAP_USER_EXIT.
Only x86 is implemented so far.
Signed-off-by: Radim Krčmář <rkrcmar@xxxxxxxxxx>
---
v2:
* use vcpu ioctl instead of vm one [4/5]
* shrink kvm_user_exit from 64 to 32 bytes [4/5]
Documentation/virtual/kvm/api.txt | 30 ++++++++++++++++++++++++++++++
arch/x86/kvm/x86.c | 24 ++++++++++++++++++++++++
include/uapi/linux/kvm.h | 7 +++++++
virt/kvm/kvm_main.c | 5 +++--
4 files changed, 64 insertions(+), 2 deletions(-)
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 3c714d43a717..c5844f0b8e7c 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -3020,6 +3020,36 @@ Returns: 0 on success, -1 on error
Queues an SMI on the thread's vcpu.
+
+4.97 KVM_USER_EXIT
+
+Capability: KVM_CAP_USER_EXIT
+Architectures: x86
+Type: vcpu ioctl
+Parameters: struct kvm_user_exit (in)
+Returns: 0 on success,
+ -EFAULT if the parameter couldn't be read,
+ -EINVAL if 'reserved' is not zeroed,
+
+struct kvm_user_exit {
+ __u8 reserved[32];
+};
+
+The ioctl is asynchronous to VCPU execution and can be issued from all threads.
+
+Make vcpu_id exit to userspace as soon as possible. If the VCPU is not running
+in kernel at the time, it will exit early on the next call to KVM_RUN.
+If the VCPU was going to exit because of other reasons when KVM_USER_EXIT was
+issued, it will keep the original exit reason and not exit early on next
+KVM_RUN.
+If VCPU exited because of KVM_USER_EXIT, the exit reason is KVM_EXIT_REQUEST.
+
+This ioctl has very similar effect (same sans some races on userspace exit) as
+sending a signal (that is blocked in userspace and set in KVM_SET_SIGNAL_MASK)
+to the VCPU thread.
+
+
+
5. The kvm_run structure
------------------------
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3493457ad0a1..27d777eb34e4 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2466,6 +2466,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
case KVM_CAP_ASSIGN_DEV_IRQ:
case KVM_CAP_PCI_2_3:
#endif
+ case KVM_CAP_USER_EXIT:
r = 1;
break;
case KVM_CAP_X86_SMM:
@@ -3077,6 +3078,20 @@ static int kvm_set_guest_paused(struct kvm_vcpu *vcpu)
return 0;
}
+int kvm_vcpu_ioctl_user_exit(struct kvm_vcpu *vcpu, struct kvm_user_exit *info)
+{
+ struct kvm_user_exit valid = {};
+ BUILD_BUG_ON(sizeof(valid) != 32);
+
+ if (memcmp(info, &valid, sizeof(valid)))
+ return -EINVAL;
+
+ kvm_make_request(KVM_REQ_EXIT, vcpu);
+ kvm_vcpu_kick(vcpu);
+
+ return 0;
+}
+
long kvm_arch_vcpu_ioctl(struct file *filp,
unsigned int ioctl, unsigned long arg)
{
@@ -3341,6 +3356,15 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
r = kvm_set_guest_paused(vcpu);
goto out;
}
+ case KVM_USER_EXIT: {
+ struct kvm_user_exit info;
+
+ r = -EFAULT;
+ if (copy_from_user(&info, argp, sizeof(info)))
+ goto out;
+ r = kvm_vcpu_ioctl_user_exit(vcpu, &info);
+ break;
+ }
default:
r = -EINVAL;
}
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index d996a7cdb4d2..bc5a1abe9626 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -826,6 +826,7 @@ struct kvm_ppc_smmu_info {
#define KVM_CAP_X86_SMM 117
#define KVM_CAP_MULTI_ADDRESS_SPACE 118
#define KVM_CAP_SPLIT_IRQCHIP 119
+#define KVM_CAP_USER_EXIT 120
#ifdef KVM_CAP_IRQ_ROUTING
@@ -1008,6 +1009,10 @@ struct kvm_device_attr {
__u64 addr; /* userspace address of attr data */
};
+struct kvm_user_exit {
+ __u8 reserved[32];
+};
+
#define KVM_DEV_VFIO_GROUP 1
#define KVM_DEV_VFIO_GROUP_ADD 1
#define KVM_DEV_VFIO_GROUP_DEL 2
@@ -1119,6 +1124,8 @@ struct kvm_s390_ucas_mapping {
#define KVM_ARM_SET_DEVICE_ADDR _IOW(KVMIO, 0xab, struct kvm_arm_device_addr)
/* Available with KVM_CAP_PPC_RTAS */
#define KVM_PPC_RTAS_DEFINE_TOKEN _IOW(KVMIO, 0xac, struct kvm_rtas_token_args)
+/* Available with KVM_CAP_USER_EXIT */
+#define KVM_USER_EXIT _IOW(KVMIO, 0xad, struct kvm_user_exit)
/* ioctl for vm fd */
#define KVM_CREATE_DEVICE _IOWR(KVMIO, 0xe0, struct kvm_create_device)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index b34a328fdac1..d7ffe6090520 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2248,15 +2248,16 @@ static long kvm_vcpu_ioctl(struct file *filp,
if (unlikely(_IOC_TYPE(ioctl) != KVMIO))
return -EINVAL;
-#if defined(CONFIG_S390) || defined(CONFIG_PPC) || defined(CONFIG_MIPS)
/*
* Special cases: vcpu ioctls that are asynchronous to vcpu execution,
* so vcpu_load() would break it.
*/
+#if defined(CONFIG_S390) || defined(CONFIG_PPC) || defined(CONFIG_MIPS)
if (ioctl == KVM_S390_INTERRUPT || ioctl == KVM_S390_IRQ || ioctl == KVM_INTERRUPT)
return kvm_arch_vcpu_ioctl(filp, ioctl, arg);
#endif
-
+ if (ioctl == KVM_USER_EXIT)
+ return kvm_arch_vcpu_ioctl(filp, ioctl, arg);
r = vcpu_load(vcpu);
if (r)
--
2.5.0
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