On Thu, Apr 18, 2019 at 12:39:42PM +0200, Cédric Le Goater wrote:
> When a P9 sPAPR VM boots, the CAS negotiation process determines which
> interrupt mode to use (XICS legacy or XIVE native) and invokes a
> machine reset to activate the chosen mode.
>
> We introduce 'release' methods for the XICS-on-XIVE and the XIVE
> native KVM devices which are called when the file descriptor of the
> device is closed after the TIMA and ESB pages have been unmapped.
> They perform the necessary cleanups : clear the vCPU interrupt
> presenters that could be attached and then destroy the device. The
> 'release' methods replace the 'destroy' methods as 'destroy' is not
> called anymore once 'release' is. Compatibility with older QEMU is
> nevertheless maintained.
>
> This is not considered as a safe operation as the vCPUs are still
> running and could be referencing the KVM device through their
> presenters. To protect the system from any breakage, the kvmppc_xive
> objects representing both KVM devices are now stored in an array under
> the VM. Allocation is performed on first usage and memory is freed
> only when the VM exits.
>
> Signed-off-by: Cédric Le Goater <clg@xxxxxxxx>
Reviewed-by: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx>
> ---
>
> Changes since v5 :
>
> - replaced the kvmppc_xive device array with named kvmppc_xive structs.
> - in kvmppc_xive_cleanup_vcpu(), replaced xc->xive by vcpu->kvm->arch.xive
> which is always valid in this context
> - in kvmppc_xive_release(), removed the comment on the race. The
> device being destroyed when the fd is closed, dev->private should
> always be valid when used. Also removed the kick_all_cpus_sync() to
> flush the IPIs.
> - in the both release operation, removed the test on &kvm->online_vcpus.
> - devices are now freed when the machine exits.
>
> arch/powerpc/include/asm/kvm_host.h | 6 ++-
> arch/powerpc/kvm/book3s_xive.h | 1 +
> arch/powerpc/kvm/book3s_xive.c | 67 ++++++++++++++++++++++++---
> arch/powerpc/kvm/book3s_xive_native.c | 28 +++++++++--
> arch/powerpc/kvm/powerpc.c | 9 ++++
> 5 files changed, 99 insertions(+), 12 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
> index 9cc6abdce1b9..c7abc7c3c6cd 100644
> --- a/arch/powerpc/include/asm/kvm_host.h
> +++ b/arch/powerpc/include/asm/kvm_host.h
> @@ -313,7 +313,11 @@ struct kvm_arch {
> #endif
> #ifdef CONFIG_KVM_XICS
> struct kvmppc_xics *xics;
> - struct kvmppc_xive *xive;
> + struct kvmppc_xive *xive; /* Current XIVE device in use */
> + struct {
> + struct kvmppc_xive *native;
> + struct kvmppc_xive *xics_on_xive;
> + } xive_devices;
> struct kvmppc_passthru_irqmap *pimap;
> #endif
> struct kvmppc_ops *kvm_ops;
> diff --git a/arch/powerpc/kvm/book3s_xive.h b/arch/powerpc/kvm/book3s_xive.h
> index e011622dc038..426146332984 100644
> --- a/arch/powerpc/kvm/book3s_xive.h
> +++ b/arch/powerpc/kvm/book3s_xive.h
> @@ -283,6 +283,7 @@ void kvmppc_xive_free_sources(struct kvmppc_xive_src_block *sb);
> int kvmppc_xive_select_target(struct kvm *kvm, u32 *server, u8 prio);
> int kvmppc_xive_attach_escalation(struct kvm_vcpu *vcpu, u8 prio,
> bool single_escalation);
> +struct kvmppc_xive *kvmppc_xive_get_device(struct kvm *kvm, u32 type);
>
> #endif /* CONFIG_KVM_XICS */
> #endif /* _KVM_PPC_BOOK3S_XICS_H */
> diff --git a/arch/powerpc/kvm/book3s_xive.c b/arch/powerpc/kvm/book3s_xive.c
> index 480a3fc6b9fd..922689b768e6 100644
> --- a/arch/powerpc/kvm/book3s_xive.c
> +++ b/arch/powerpc/kvm/book3s_xive.c
> @@ -1100,9 +1100,15 @@ void kvmppc_xive_disable_vcpu_interrupts(struct kvm_vcpu *vcpu)
> void kvmppc_xive_cleanup_vcpu(struct kvm_vcpu *vcpu)
> {
> struct kvmppc_xive_vcpu *xc = vcpu->arch.xive_vcpu;
> - struct kvmppc_xive *xive = xc->xive;
> + struct kvmppc_xive *xive = vcpu->kvm->arch.xive;
> int i;
>
> + if (!kvmppc_xics_enabled(vcpu))
> + return;
> +
> + if (!xc)
> + return;
> +
> pr_devel("cleanup_vcpu(cpu=%d)\n", xc->server_num);
>
> /* Ensure no interrupt is still routed to that VP */
> @@ -1141,6 +1147,10 @@ void kvmppc_xive_cleanup_vcpu(struct kvm_vcpu *vcpu)
> }
> /* Free the VP */
> kfree(xc);
> +
> + /* Cleanup the vcpu */
> + vcpu->arch.irq_type = KVMPPC_IRQ_DEFAULT;
> + vcpu->arch.xive_vcpu = NULL;
> }
>
> int kvmppc_xive_connect_vcpu(struct kvm_device *dev,
> @@ -1158,7 +1168,7 @@ int kvmppc_xive_connect_vcpu(struct kvm_device *dev,
> }
> if (xive->kvm != vcpu->kvm)
> return -EPERM;
> - if (vcpu->arch.irq_type)
> + if (vcpu->arch.irq_type != KVMPPC_IRQ_DEFAULT)
> return -EBUSY;
> if (kvmppc_xive_find_server(vcpu->kvm, cpu)) {
> pr_devel("Duplicate !\n");
> @@ -1824,12 +1834,26 @@ void kvmppc_xive_free_sources(struct kvmppc_xive_src_block *sb)
> }
> }
>
> -static void kvmppc_xive_free(struct kvm_device *dev)
> +/*
> + * Called when device fd is closed
> + */
> +static void kvmppc_xive_release(struct kvm_device *dev)
> {
> struct kvmppc_xive *xive = dev->private;
> struct kvm *kvm = xive->kvm;
> + struct kvm_vcpu *vcpu;
> int i;
>
> + pr_devel("Releasing xive device\n");
> +
> + /*
> + * When releasing the KVM device fd, the vCPUs can still be
> + * running and we should clean up the vCPU interrupt
> + * presenters first.
> + */
> + kvm_for_each_vcpu(i, vcpu, kvm)
> + kvmppc_xive_cleanup_vcpu(vcpu);
> +
> debugfs_remove(xive->dentry);
>
> if (kvm)
> @@ -1846,11 +1870,42 @@ static void kvmppc_xive_free(struct kvm_device *dev)
> if (xive->vp_base != XIVE_INVALID_VP)
> xive_native_free_vp_block(xive->vp_base);
>
> + /*
> + * A reference of the kvmppc_xive pointer is now kept under
> + * the xive_devices struct of the machine for reuse. It is
> + * freed when the VM is destroyed for now until we fix all the
> + * execution paths.
> + */
>
> - kfree(xive);
> kfree(dev);
> }
>
> +/*
> + * When the guest chooses the interrupt mode (XICS legacy or XIVE
> + * native), the VM will switch of KVM device. The previous device will
> + * be "released" before the new one is created.
> + *
> + * Until we are sure all execution paths are well protected, provide a
> + * fail safe (transitional) method for device destruction, in which
> + * the XIVE device pointer is recycled and not directly freed.
> + */
> +struct kvmppc_xive *kvmppc_xive_get_device(struct kvm *kvm, u32 type)
> +{
> + struct kvmppc_xive **kvm_xive_device = type == KVM_DEV_TYPE_XIVE ?
> + &kvm->arch.xive_devices.native :
> + &kvm->arch.xive_devices.xics_on_xive;
> + struct kvmppc_xive *xive = *kvm_xive_device;
> +
> + if (!xive) {
> + xive = kzalloc(sizeof(*xive), GFP_KERNEL);
> + *kvm_xive_device = xive;
> + } else {
> + memset(xive, 0, sizeof(*xive));
> + }
> +
> + return xive;
> +}
> +
> static int kvmppc_xive_create(struct kvm_device *dev, u32 type)
> {
> struct kvmppc_xive *xive;
> @@ -1859,7 +1914,7 @@ static int kvmppc_xive_create(struct kvm_device *dev, u32 type)
>
> pr_devel("Creating xive for partition\n");
>
> - xive = kzalloc(sizeof(*xive), GFP_KERNEL);
> + xive = kvmppc_xive_get_device(kvm, type);
> if (!xive)
> return -ENOMEM;
>
> @@ -2024,7 +2079,7 @@ struct kvm_device_ops kvm_xive_ops = {
> .name = "kvm-xive",
> .create = kvmppc_xive_create,
> .init = kvmppc_xive_init,
> - .destroy = kvmppc_xive_free,
> + .release = kvmppc_xive_release,
> .set_attr = xive_set_attr,
> .get_attr = xive_get_attr,
> .has_attr = xive_has_attr,
> diff --git a/arch/powerpc/kvm/book3s_xive_native.c b/arch/powerpc/kvm/book3s_xive_native.c
> index 62648f833adf..0497272a72fa 100644
> --- a/arch/powerpc/kvm/book3s_xive_native.c
> +++ b/arch/powerpc/kvm/book3s_xive_native.c
> @@ -964,15 +964,27 @@ static int kvmppc_xive_native_has_attr(struct kvm_device *dev,
> return -ENXIO;
> }
>
> -static void kvmppc_xive_native_free(struct kvm_device *dev)
> +/*
> + * Called when device fd is closed
> + */
> +static void kvmppc_xive_native_release(struct kvm_device *dev)
> {
> struct kvmppc_xive *xive = dev->private;
> struct kvm *kvm = xive->kvm;
> + struct kvm_vcpu *vcpu;
> int i;
>
> debugfs_remove(xive->dentry);
>
> - pr_devel("Destroying xive native device\n");
> + pr_devel("Releasing xive native device\n");
> +
> + /*
> + * When releasing the KVM device fd, the vCPUs can still be
> + * running and we should clean up the vCPU interrupt
> + * presenters first.
> + */
> + kvm_for_each_vcpu(i, vcpu, kvm)
> + kvmppc_xive_native_cleanup_vcpu(vcpu);
>
> if (kvm)
> kvm->arch.xive = NULL;
> @@ -987,7 +999,13 @@ static void kvmppc_xive_native_free(struct kvm_device *dev)
> if (xive->vp_base != XIVE_INVALID_VP)
> xive_native_free_vp_block(xive->vp_base);
>
> - kfree(xive);
> + /*
> + * A reference of the kvmppc_xive pointer is now kept under
> + * the xive_devices struct of the machine for reuse. It is
> + * freed when the VM is destroyed for now until we fix all the
> + * execution paths.
> + */
> +
> kfree(dev);
> }
>
> @@ -1002,7 +1020,7 @@ static int kvmppc_xive_native_create(struct kvm_device *dev, u32 type)
> if (kvm->arch.xive)
> return -EEXIST;
>
> - xive = kzalloc(sizeof(*xive), GFP_KERNEL);
> + xive = kvmppc_xive_get_device(kvm, type);
> if (!xive)
> return -ENOMEM;
>
> @@ -1182,7 +1200,7 @@ struct kvm_device_ops kvm_xive_native_ops = {
> .name = "kvm-xive-native",
> .create = kvmppc_xive_native_create,
> .init = kvmppc_xive_native_init,
> - .destroy = kvmppc_xive_native_free,
> + .release = kvmppc_xive_native_release,
> .set_attr = kvmppc_xive_native_set_attr,
> .get_attr = kvmppc_xive_native_get_attr,
> .has_attr = kvmppc_xive_native_has_attr,
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index f54926c78320..7f41a68d8094 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -501,6 +501,15 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
>
> mutex_unlock(&kvm->lock);
>
> + /*
> + * Free the XIVE devices which are not directly freed by the
> + * device 'release' method
> + */
> + kfree(kvm->arch.xive_devices.native);
> + kvm->arch.xive_devices.native = NULL;
> + kfree(kvm->arch.xive_devices.xics_on_xive);
> + kvm->arch.xive_devices.xics_on_xive = NULL;
> +
> /* drop the module reference */
> module_put(kvm->arch.kvm_ops->owner);
> }
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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