On Tue, Apr 09, 2019 at 04:13:46PM +0200, Cédric Le Goater wrote:
> On P9 sPAPR guests, the interrupt mode (XICS legacy or XIVE native) is
> determine at CAS time and the chosen mode is activated after a machine
> reset. To be able to switch from one mode to another, subsequent
> patches will introduce the capability to destroy the KVM device
> without destroying the VM.
>
> 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>
Although...
> ---
> arch/powerpc/include/asm/kvm_host.h | 1 +
> arch/powerpc/kvm/book3s_xive.h | 1 +
> arch/powerpc/kvm/book3s_xive.c | 23 +++++++++++++++++++++--
> arch/powerpc/kvm/book3s_xive_native.c | 9 +++++++--
> arch/powerpc/kvm/powerpc.c | 6 ++++++
> 5 files changed, 36 insertions(+), 4 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
> index 9cc6abdce1b9..ed059c95e56a 100644
> --- a/arch/powerpc/include/asm/kvm_host.h
> +++ b/arch/powerpc/include/asm/kvm_host.h
> @@ -314,6 +314,7 @@ struct kvm_arch {
> #ifdef CONFIG_KVM_XICS
> struct kvmppc_xics *xics;
> struct kvmppc_xive *xive;
> + struct kvmppc_xive *xive_devices[2];
... as noted on the previous revision, I feel this use of a
bool-indexed array instead of separate fields makes things more
confusing than necessary, for a negligible reduction in code size.
> 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..4d4e1730de84 100644
> --- a/arch/powerpc/kvm/book3s_xive.c
> +++ b/arch/powerpc/kvm/book3s_xive.c
> @@ -1846,11 +1846,30 @@ 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[] array of the machine for reuse. It is
> + * freed when the VM is destroyed.
> + */
>
> - kfree(xive);
> kfree(dev);
> }
>
> +struct kvmppc_xive *kvmppc_xive_get_device(struct kvm *kvm, u32 type)
> +{
> + struct kvmppc_xive *xive;
> + bool xive_native_index = type == KVM_DEV_TYPE_XIVE;
> +
> + xive = kvm->arch.xive_devices[xive_native_index];
> +
> + if (!xive) {
> + xive = kzalloc(sizeof(*xive), GFP_KERNEL);
> + kvm->arch.xive_devices[xive_native_index] = xive;
> + }
> +
> + return xive;
> +}
> +
> static int kvmppc_xive_create(struct kvm_device *dev, u32 type)
> {
> struct kvmppc_xive *xive;
> @@ -1859,7 +1878,7 @@ 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;
>
> diff --git a/arch/powerpc/kvm/book3s_xive_native.c b/arch/powerpc/kvm/book3s_xive_native.c
> index 62648f833adf..092db0efe628 100644
> --- a/arch/powerpc/kvm/book3s_xive_native.c
> +++ b/arch/powerpc/kvm/book3s_xive_native.c
> @@ -987,7 +987,12 @@ 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[] array of the machine for reuse. It is
> + * freed when the VM is destroyed.
> + */
> +
> kfree(dev);
> }
>
> @@ -1002,7 +1007,7 @@ 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;
>
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index f54926c78320..d0914316ddc7 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -501,6 +501,12 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
>
> mutex_unlock(&kvm->lock);
>
> + for (i = 0; i < ARRAY_SIZE(kvm->arch.xive_devices); i++) {
> + struct kvmppc_xive *xive = kvm->arch.xive_devices[i];
> + if (xive)
> + kfree(xive);
> + }
> +
> /* 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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