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Date: Wed, 5 Aug 2015 18:36:33 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: Radim Krčmář <rkrcmar@...hat.com>,
linux-kernel@...r.kernel.org
Cc: kvm@...r.kernel.org
Subject: Re: [PATCH v2 4/5] KVM: add KVM_USER_EXIT vcpu ioctl for userspace
exit
On 05/08/2015 18:33, Radim Krčmář wrote:
> 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@...hat.com>
> ---
> 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.
Can we just return EINVAL if the parameter is not NULL?
Paolo
> +
> +
> +
> 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)
>
--
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