| Message ID | 1386878149-13397-3-git-send-email-christoffer.dall@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 12/12/13 19:55, Christoffer Dall wrote: > Support creating the ARM VGIC device through the KVM_CREATE_DEVICE > ioctl, which can then later be leveraged to use the > KVM_{GET/SET}_DEVICE_ATTR, which is useful both for setting addresses in > a more generic API than the ARM-specific one and is useful for > save/restore of VGIC state. > > Adds KVM_CAP_DEVICE_CTRL to ARM capabilities. > > Note that we change the check for creating a VGIC from bailing out if > any VCPUs were created, to bailing out if any VCPUs were ever run. This > is an important distinction that shouldn't break anything, but allows > creating the VGIC after the VCPUs have been created. > > Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org> > --- > Changelog[v4]: > - Rename kvm_arm_vgic_ops to kvm_arm_vgic_v2_ops > - Add comment to kvm_vgic_create about locking vcpu->mutex > > Changelog[v3]: > - Prevent race in kvm_vgic_create by trying to take all the vcpu > locks before creating the vgic. > > Changelog[v2]: > - None > > Documentation/virtual/kvm/devices/arm-vgic.txt | 10 ++++ > arch/arm/kvm/arm.c | 1 + > include/linux/kvm_host.h | 1 + > include/uapi/linux/kvm.h | 1 + > virt/kvm/arm/vgic.c | 63 +++++++++++++++++++++++++- > virt/kvm/kvm_main.c | 6 ++- > 6 files changed, 79 insertions(+), 3 deletions(-) > create mode 100644 Documentation/virtual/kvm/devices/arm-vgic.txt > > diff --git a/Documentation/virtual/kvm/devices/arm-vgic.txt b/Documentation/virtual/kvm/devices/arm-vgic.txt > new file mode 100644 > index 0000000..38f27f7 > --- /dev/null > +++ b/Documentation/virtual/kvm/devices/arm-vgic.txt > @@ -0,0 +1,10 @@ > +ARM Virtual Generic Interrupt Controller (VGIC) > +=============================================== > + > +Device types supported: > + KVM_DEV_TYPE_ARM_VGIC_V2 ARM Generic Interrupt Controller v2.0 > + > +Only one VGIC instance may be instantiated through either this API or the > +legacy KVM_CREATE_IRQCHIP api. The created VGIC will act as the VM interrupt > +controller, requiring emulated user-space devices to inject interrupts to the > +VGIC instead of directly to CPUs. > diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c > index c9fe9d7..cc7c41a 100644 > --- a/arch/arm/kvm/arm.c > +++ b/arch/arm/kvm/arm.c > @@ -190,6 +190,7 @@ int kvm_dev_ioctl_check_extension(long ext) > case KVM_CAP_IRQCHIP: > r = vgic_present; > break; > + case KVM_CAP_DEVICE_CTRL: > case KVM_CAP_USER_MEMORY: > case KVM_CAP_SYNC_MMU: > case KVM_CAP_DESTROY_MEMORY_REGION_WORKS: > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index 9523d2a..521dd76 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -1076,6 +1076,7 @@ struct kvm_device *kvm_device_from_filp(struct file *filp); > extern struct kvm_device_ops kvm_mpic_ops; > extern struct kvm_device_ops kvm_xics_ops; > extern struct kvm_device_ops kvm_vfio_ops; > +extern struct kvm_device_ops kvm_arm_vgic_v2_ops; > > #ifdef CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT > > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h > index 902f124..b647c29 100644 > --- a/include/uapi/linux/kvm.h > +++ b/include/uapi/linux/kvm.h > @@ -853,6 +853,7 @@ struct kvm_device_attr { > #define KVM_DEV_VFIO_GROUP 1 > #define KVM_DEV_VFIO_GROUP_ADD 1 > #define KVM_DEV_VFIO_GROUP_DEL 2 > +#define KVM_DEV_TYPE_ARM_VGIC_V2 5 > > /* > * ioctls for VM fds > diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c > index 5e9df47..b15d6c1 100644 > --- a/virt/kvm/arm/vgic.c > +++ b/virt/kvm/arm/vgic.c > @@ -1433,20 +1433,45 @@ out: > > int kvm_vgic_create(struct kvm *kvm) > { > - int ret = 0; > + int i, vcpu_lock_idx = -1, ret = 0; > + struct kvm_vcpu *vcpu; > > mutex_lock(&kvm->lock); > > - if (atomic_read(&kvm->online_vcpus) || kvm->arch.vgic.vctrl_base) { > + if (kvm->arch.vgic.vctrl_base) { > ret = -EEXIST; > goto out; > } > > + /* > + * Any time a vcpu is run, vcpu_load is called which tries to grab the > + * vcpu->mutex. By grabbing the vcpu->mutex of all VCPUs we ensure > + * that no other VCPUs are run while we create the vgic. > + */ > + kvm_for_each_vcpu(i, vcpu, kvm) { > + if (!mutex_trylock(&vcpu->mutex)) > + goto out_unlock; > + vcpu_lock_idx = i; > + } > + > + kvm_for_each_vcpu(i, vcpu, kvm) { > + if (vcpu->arch.has_run_once) { > + ret = -EBUSY; > + goto out_unlock; > + } > + } > + > spin_lock_init(&kvm->arch.vgic.lock); > kvm->arch.vgic.vctrl_base = vgic_vctrl_base; > kvm->arch.vgic.vgic_dist_base = VGIC_ADDR_UNDEF; > kvm->arch.vgic.vgic_cpu_base = VGIC_ADDR_UNDEF; > > +out_unlock: > + for (; vcpu_lock_idx >= 0; vcpu_lock_idx--) { > + vcpu = kvm_get_vcpu(kvm, vcpu_lock_idx); > + mutex_unlock(&vcpu->mutex); > + } > + > out: > mutex_unlock(&kvm->lock); > return ret; > @@ -1510,3 +1535,37 @@ int kvm_vgic_set_addr(struct kvm *kvm, unsigned long type, u64 addr) > mutex_unlock(&kvm->lock); > return r; > } > + > +static int vgic_set_attr(struct kvm_device *dev, struct kvm_device_attr *attr) > +{ > + return -ENXIO; > +} > + > +static int vgic_get_attr(struct kvm_device *dev, struct kvm_device_attr *attr) > +{ > + return -ENXIO; > +} > + > +static int vgic_has_attr(struct kvm_device *dev, struct kvm_device_attr *attr) > +{ > + return -ENXIO; > +} > + > +static void vgic_destroy(struct kvm_device *dev) > +{ > + kfree(dev); > +} > + > +static int vgic_create(struct kvm_device *dev, u32 type) > +{ > + return kvm_vgic_create(dev->kvm); > +} > + > +struct kvm_device_ops kvm_arm_vgic_v2_ops = { > + .name = "kvm-arm-vgic", > + .create = vgic_create, > + .destroy = vgic_destroy, > + .set_attr = vgic_set_attr, > + .get_attr = vgic_get_attr, > + .has_attr = vgic_has_attr, > +}; > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index a0aa84b..954a0ba 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -2279,7 +2279,11 @@ static int kvm_ioctl_create_device(struct kvm *kvm, > #ifdef CONFIG_KVM_VFIO > case KVM_DEV_TYPE_VFIO: > ops = &kvm_vfio_ops; > - break; I think you just broke VFIO. > +#endif > +#ifdef CONFIG_KVM_ARM_VGIC > + case KVM_DEV_TYPE_ARM_VGIC_V2: > + ops = &kvm_arm_vgic_v2_ops; > + break; Indentation? > #endif > default: > return -ENODEV; > Provided that you fix the above: Acked-by: Marc Zyngier <marc.zyngier@arm.com> M.
On Mon, Dec 16, 2013 at 11:45:21AM +0000, Marc Zyngier wrote: > On 12/12/13 19:55, Christoffer Dall wrote: > > Support creating the ARM VGIC device through the KVM_CREATE_DEVICE > > ioctl, which can then later be leveraged to use the > > KVM_{GET/SET}_DEVICE_ATTR, which is useful both for setting addresses in > > a more generic API than the ARM-specific one and is useful for > > save/restore of VGIC state. > > > > Adds KVM_CAP_DEVICE_CTRL to ARM capabilities. > > > > Note that we change the check for creating a VGIC from bailing out if > > any VCPUs were created, to bailing out if any VCPUs were ever run. This > > is an important distinction that shouldn't break anything, but allows > > creating the VGIC after the VCPUs have been created. > > > > Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org> > > --- > > Changelog[v4]: > > - Rename kvm_arm_vgic_ops to kvm_arm_vgic_v2_ops > > - Add comment to kvm_vgic_create about locking vcpu->mutex > > > > Changelog[v3]: > > - Prevent race in kvm_vgic_create by trying to take all the vcpu > > locks before creating the vgic. > > > > Changelog[v2]: > > - None > > > > Documentation/virtual/kvm/devices/arm-vgic.txt | 10 ++++ > > arch/arm/kvm/arm.c | 1 + > > include/linux/kvm_host.h | 1 + > > include/uapi/linux/kvm.h | 1 + > > virt/kvm/arm/vgic.c | 63 +++++++++++++++++++++++++- > > virt/kvm/kvm_main.c | 6 ++- > > 6 files changed, 79 insertions(+), 3 deletions(-) > > create mode 100644 Documentation/virtual/kvm/devices/arm-vgic.txt > > > > diff --git a/Documentation/virtual/kvm/devices/arm-vgic.txt b/Documentation/virtual/kvm/devices/arm-vgic.txt > > new file mode 100644 > > index 0000000..38f27f7 > > --- /dev/null > > +++ b/Documentation/virtual/kvm/devices/arm-vgic.txt > > @@ -0,0 +1,10 @@ > > +ARM Virtual Generic Interrupt Controller (VGIC) > > +=============================================== > > + > > +Device types supported: > > + KVM_DEV_TYPE_ARM_VGIC_V2 ARM Generic Interrupt Controller v2.0 > > + > > +Only one VGIC instance may be instantiated through either this API or the > > +legacy KVM_CREATE_IRQCHIP api. The created VGIC will act as the VM interrupt > > +controller, requiring emulated user-space devices to inject interrupts to the > > +VGIC instead of directly to CPUs. > > diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c > > index c9fe9d7..cc7c41a 100644 > > --- a/arch/arm/kvm/arm.c > > +++ b/arch/arm/kvm/arm.c > > @@ -190,6 +190,7 @@ int kvm_dev_ioctl_check_extension(long ext) > > case KVM_CAP_IRQCHIP: > > r = vgic_present; > > break; > > + case KVM_CAP_DEVICE_CTRL: > > case KVM_CAP_USER_MEMORY: > > case KVM_CAP_SYNC_MMU: > > case KVM_CAP_DESTROY_MEMORY_REGION_WORKS: > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > > index 9523d2a..521dd76 100644 > > --- a/include/linux/kvm_host.h > > +++ b/include/linux/kvm_host.h > > @@ -1076,6 +1076,7 @@ struct kvm_device *kvm_device_from_filp(struct file *filp); > > extern struct kvm_device_ops kvm_mpic_ops; > > extern struct kvm_device_ops kvm_xics_ops; > > extern struct kvm_device_ops kvm_vfio_ops; > > +extern struct kvm_device_ops kvm_arm_vgic_v2_ops; > > > > #ifdef CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT > > > > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h > > index 902f124..b647c29 100644 > > --- a/include/uapi/linux/kvm.h > > +++ b/include/uapi/linux/kvm.h > > @@ -853,6 +853,7 @@ struct kvm_device_attr { > > #define KVM_DEV_VFIO_GROUP 1 > > #define KVM_DEV_VFIO_GROUP_ADD 1 > > #define KVM_DEV_VFIO_GROUP_DEL 2 > > +#define KVM_DEV_TYPE_ARM_VGIC_V2 5 > > > > /* > > * ioctls for VM fds > > diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c > > index 5e9df47..b15d6c1 100644 > > --- a/virt/kvm/arm/vgic.c > > +++ b/virt/kvm/arm/vgic.c > > @@ -1433,20 +1433,45 @@ out: > > > > int kvm_vgic_create(struct kvm *kvm) > > { > > - int ret = 0; > > + int i, vcpu_lock_idx = -1, ret = 0; > > + struct kvm_vcpu *vcpu; > > > > mutex_lock(&kvm->lock); > > > > - if (atomic_read(&kvm->online_vcpus) || kvm->arch.vgic.vctrl_base) { > > + if (kvm->arch.vgic.vctrl_base) { > > ret = -EEXIST; > > goto out; > > } > > > > + /* > > + * Any time a vcpu is run, vcpu_load is called which tries to grab the > > + * vcpu->mutex. By grabbing the vcpu->mutex of all VCPUs we ensure > > + * that no other VCPUs are run while we create the vgic. > > + */ > > + kvm_for_each_vcpu(i, vcpu, kvm) { > > + if (!mutex_trylock(&vcpu->mutex)) > > + goto out_unlock; > > + vcpu_lock_idx = i; > > + } > > + > > + kvm_for_each_vcpu(i, vcpu, kvm) { > > + if (vcpu->arch.has_run_once) { > > + ret = -EBUSY; > > + goto out_unlock; > > + } > > + } > > + > > spin_lock_init(&kvm->arch.vgic.lock); > > kvm->arch.vgic.vctrl_base = vgic_vctrl_base; > > kvm->arch.vgic.vgic_dist_base = VGIC_ADDR_UNDEF; > > kvm->arch.vgic.vgic_cpu_base = VGIC_ADDR_UNDEF; > > > > +out_unlock: > > + for (; vcpu_lock_idx >= 0; vcpu_lock_idx--) { > > + vcpu = kvm_get_vcpu(kvm, vcpu_lock_idx); > > + mutex_unlock(&vcpu->mutex); > > + } > > + > > out: > > mutex_unlock(&kvm->lock); > > return ret; > > @@ -1510,3 +1535,37 @@ int kvm_vgic_set_addr(struct kvm *kvm, unsigned long type, u64 addr) > > mutex_unlock(&kvm->lock); > > return r; > > } > > + > > +static int vgic_set_attr(struct kvm_device *dev, struct kvm_device_attr *attr) > > +{ > > + return -ENXIO; > > +} > > + > > +static int vgic_get_attr(struct kvm_device *dev, struct kvm_device_attr *attr) > > +{ > > + return -ENXIO; > > +} > > + > > +static int vgic_has_attr(struct kvm_device *dev, struct kvm_device_attr *attr) > > +{ > > + return -ENXIO; > > +} > > + > > +static void vgic_destroy(struct kvm_device *dev) > > +{ > > + kfree(dev); > > +} > > + > > +static int vgic_create(struct kvm_device *dev, u32 type) > > +{ > > + return kvm_vgic_create(dev->kvm); > > +} > > + > > +struct kvm_device_ops kvm_arm_vgic_v2_ops = { > > + .name = "kvm-arm-vgic", > > + .create = vgic_create, > > + .destroy = vgic_destroy, > > + .set_attr = vgic_set_attr, > > + .get_attr = vgic_get_attr, > > + .has_attr = vgic_has_attr, > > +}; > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > > index a0aa84b..954a0ba 100644 > > --- a/virt/kvm/kvm_main.c > > +++ b/virt/kvm/kvm_main.c > > @@ -2279,7 +2279,11 @@ static int kvm_ioctl_create_device(struct kvm *kvm, > > #ifdef CONFIG_KVM_VFIO > > case KVM_DEV_TYPE_VFIO: > > ops = &kvm_vfio_ops; > > - break; > > I think you just broke VFIO. > Yeah, I'm tired of thinking about VFIO for platform devices so I just deided to get rid of that stuff ;) > > +#endif > > +#ifdef CONFIG_KVM_ARM_VGIC > > + case KVM_DEV_TYPE_ARM_VGIC_V2: > > + ops = &kvm_arm_vgic_v2_ops; > > + break; > > Indentation? > I have no idea what was in that coffee... > > #endif > > default: > > return -ENODEV; > > > > Provided that you fix the above: > Acked-by: Marc Zyngier <marc.zyngier@arm.com> > Thanks,
diff --git a/Documentation/virtual/kvm/devices/arm-vgic.txt b/Documentation/virtual/kvm/devices/arm-vgic.txt new file mode 100644 index 0000000..38f27f7 --- /dev/null +++ b/Documentation/virtual/kvm/devices/arm-vgic.txt @@ -0,0 +1,10 @@ +ARM Virtual Generic Interrupt Controller (VGIC) +=============================================== + +Device types supported: + KVM_DEV_TYPE_ARM_VGIC_V2 ARM Generic Interrupt Controller v2.0 + +Only one VGIC instance may be instantiated through either this API or the +legacy KVM_CREATE_IRQCHIP api. The created VGIC will act as the VM interrupt +controller, requiring emulated user-space devices to inject interrupts to the +VGIC instead of directly to CPUs. diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c index c9fe9d7..cc7c41a 100644 --- a/arch/arm/kvm/arm.c +++ b/arch/arm/kvm/arm.c @@ -190,6 +190,7 @@ int kvm_dev_ioctl_check_extension(long ext) case KVM_CAP_IRQCHIP: r = vgic_present; break; + case KVM_CAP_DEVICE_CTRL: case KVM_CAP_USER_MEMORY: case KVM_CAP_SYNC_MMU: case KVM_CAP_DESTROY_MEMORY_REGION_WORKS: diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 9523d2a..521dd76 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -1076,6 +1076,7 @@ struct kvm_device *kvm_device_from_filp(struct file *filp); extern struct kvm_device_ops kvm_mpic_ops; extern struct kvm_device_ops kvm_xics_ops; extern struct kvm_device_ops kvm_vfio_ops; +extern struct kvm_device_ops kvm_arm_vgic_v2_ops; #ifdef CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index 902f124..b647c29 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -853,6 +853,7 @@ struct kvm_device_attr { #define KVM_DEV_VFIO_GROUP 1 #define KVM_DEV_VFIO_GROUP_ADD 1 #define KVM_DEV_VFIO_GROUP_DEL 2 +#define KVM_DEV_TYPE_ARM_VGIC_V2 5 /* * ioctls for VM fds diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c index 5e9df47..b15d6c1 100644 --- a/virt/kvm/arm/vgic.c +++ b/virt/kvm/arm/vgic.c @@ -1433,20 +1433,45 @@ out: int kvm_vgic_create(struct kvm *kvm) { - int ret = 0; + int i, vcpu_lock_idx = -1, ret = 0; + struct kvm_vcpu *vcpu; mutex_lock(&kvm->lock); - if (atomic_read(&kvm->online_vcpus) || kvm->arch.vgic.vctrl_base) { + if (kvm->arch.vgic.vctrl_base) { ret = -EEXIST; goto out; } + /* + * Any time a vcpu is run, vcpu_load is called which tries to grab the + * vcpu->mutex. By grabbing the vcpu->mutex of all VCPUs we ensure + * that no other VCPUs are run while we create the vgic. + */ + kvm_for_each_vcpu(i, vcpu, kvm) { + if (!mutex_trylock(&vcpu->mutex)) + goto out_unlock; + vcpu_lock_idx = i; + } + + kvm_for_each_vcpu(i, vcpu, kvm) { + if (vcpu->arch.has_run_once) { + ret = -EBUSY; + goto out_unlock; + } + } + spin_lock_init(&kvm->arch.vgic.lock); kvm->arch.vgic.vctrl_base = vgic_vctrl_base; kvm->arch.vgic.vgic_dist_base = VGIC_ADDR_UNDEF; kvm->arch.vgic.vgic_cpu_base = VGIC_ADDR_UNDEF; +out_unlock: + for (; vcpu_lock_idx >= 0; vcpu_lock_idx--) { + vcpu = kvm_get_vcpu(kvm, vcpu_lock_idx); + mutex_unlock(&vcpu->mutex); + } + out: mutex_unlock(&kvm->lock); return ret; @@ -1510,3 +1535,37 @@ int kvm_vgic_set_addr(struct kvm *kvm, unsigned long type, u64 addr) mutex_unlock(&kvm->lock); return r; } + +static int vgic_set_attr(struct kvm_device *dev, struct kvm_device_attr *attr) +{ + return -ENXIO; +} + +static int vgic_get_attr(struct kvm_device *dev, struct kvm_device_attr *attr) +{ + return -ENXIO; +} + +static int vgic_has_attr(struct kvm_device *dev, struct kvm_device_attr *attr) +{ + return -ENXIO; +} + +static void vgic_destroy(struct kvm_device *dev) +{ + kfree(dev); +} + +static int vgic_create(struct kvm_device *dev, u32 type) +{ + return kvm_vgic_create(dev->kvm); +} + +struct kvm_device_ops kvm_arm_vgic_v2_ops = { + .name = "kvm-arm-vgic", + .create = vgic_create, + .destroy = vgic_destroy, + .set_attr = vgic_set_attr, + .get_attr = vgic_get_attr, + .has_attr = vgic_has_attr, +}; diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index a0aa84b..954a0ba 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2279,7 +2279,11 @@ static int kvm_ioctl_create_device(struct kvm *kvm, #ifdef CONFIG_KVM_VFIO case KVM_DEV_TYPE_VFIO: ops = &kvm_vfio_ops; - break; +#endif +#ifdef CONFIG_KVM_ARM_VGIC + case KVM_DEV_TYPE_ARM_VGIC_V2: + ops = &kvm_arm_vgic_v2_ops; + break; #endif default: return -ENODEV;
Support creating the ARM VGIC device through the KVM_CREATE_DEVICE ioctl, which can then later be leveraged to use the KVM_{GET/SET}_DEVICE_ATTR, which is useful both for setting addresses in a more generic API than the ARM-specific one and is useful for save/restore of VGIC state. Adds KVM_CAP_DEVICE_CTRL to ARM capabilities. Note that we change the check for creating a VGIC from bailing out if any VCPUs were created, to bailing out if any VCPUs were ever run. This is an important distinction that shouldn't break anything, but allows creating the VGIC after the VCPUs have been created. Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org> --- Changelog[v4]: - Rename kvm_arm_vgic_ops to kvm_arm_vgic_v2_ops - Add comment to kvm_vgic_create about locking vcpu->mutex Changelog[v3]: - Prevent race in kvm_vgic_create by trying to take all the vcpu locks before creating the vgic. Changelog[v2]: - None Documentation/virtual/kvm/devices/arm-vgic.txt | 10 ++++ arch/arm/kvm/arm.c | 1 + include/linux/kvm_host.h | 1 + include/uapi/linux/kvm.h | 1 + virt/kvm/arm/vgic.c | 63 +++++++++++++++++++++++++- virt/kvm/kvm_main.c | 6 ++- 6 files changed, 79 insertions(+), 3 deletions(-) create mode 100644 Documentation/virtual/kvm/devices/arm-vgic.txt