Re: [PATCH 2/2] KVM: PPC: Book3S HV: XIVE: Set kvm->arch.xive when VPs are allocated

["Cédric Le Goater" <clg@kaod.org>]

On 10/09/2019 15:44, Greg Kurz wrote:
> If we cannot allocate the XIVE VPs in OPAL, the creation of a XIVE or
> XICS-on-XIVE device is aborted as expected, but we leave kvm->arch.xive
> set forever since the relase method isn't called in this case. Any
> subsequent tentative to create a XIVE or XICS-on-XIVE for this VM will
> thus always fail. This is a problem for QEMU since it destroys and
> re-creates these devices when the VM is reset: the VM would be
> restricted to using the emulated XIVE or XICS forever.
> 
> As an alternative to adding rollback, do not assign kvm->arch.xive before
> making sure the XIVE VPs are allocated in OPAL.
> 
> Fixes: 5422e95103cf ("KVM: PPC: Book3S HV: XIVE: Replace the 'destroy' method by a 'release' method")
> Signed-off-by: Greg Kurz <groug@kaod.org>


Reviewed-by: Cédric Le Goater <clg@kaod.org>

Thanks,

C.

> ---
>  arch/powerpc/kvm/book3s_xive.c        |   11 +++++------
>  arch/powerpc/kvm/book3s_xive_native.c |    2 +-
>  2 files changed, 6 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/powerpc/kvm/book3s_xive.c b/arch/powerpc/kvm/book3s_xive.c
> index cd2006bfcd3e..2ef43d037a4f 100644
> --- a/arch/powerpc/kvm/book3s_xive.c
> +++ b/arch/powerpc/kvm/book3s_xive.c
> @@ -2006,6 +2006,10 @@ static int kvmppc_xive_create(struct kvm_device *dev, u32 type)
>  
>  	pr_devel("Creating xive for partition\n");
>  
> +	/* Already there ? */
> +	if (kvm->arch.xive)
> +		return -EEXIST;
> +
>  	xive = kvmppc_xive_get_device(kvm, type);
>  	if (!xive)
>  		return -ENOMEM;
> @@ -2014,12 +2018,6 @@ static int kvmppc_xive_create(struct kvm_device *dev, u32 type)
>  	xive->kvm = kvm;
>  	mutex_init(&xive->lock);
>  
> -	/* Already there ? */
> -	if (kvm->arch.xive)
> -		ret = -EEXIST;
> -	else
> -		kvm->arch.xive = xive;
> -
>  	/* We use the default queue size set by the host */
>  	xive->q_order = xive_native_default_eq_shift();
>  	if (xive->q_order < PAGE_SHIFT)
> @@ -2040,6 +2038,7 @@ static int kvmppc_xive_create(struct kvm_device *dev, u32 type)
>  		return ret;
>  
>  	dev->private = xive;
> +	kvm->arch.xive = xive;
>  	return 0;
>  }
>  
> diff --git a/arch/powerpc/kvm/book3s_xive_native.c b/arch/powerpc/kvm/book3s_xive_native.c
> index e9cbb42de424..84a354b90f60 100644
> --- a/arch/powerpc/kvm/book3s_xive_native.c
> +++ b/arch/powerpc/kvm/book3s_xive_native.c
> @@ -1087,7 +1087,6 @@ static int kvmppc_xive_native_create(struct kvm_device *dev, u32 type)
>  
>  	xive->dev = dev;
>  	xive->kvm = kvm;
> -	kvm->arch.xive = xive;
>  	mutex_init(&xive->mapping_lock);
>  	mutex_init(&xive->lock);
>  
> @@ -1109,6 +1108,7 @@ static int kvmppc_xive_native_create(struct kvm_device *dev, u32 type)
>  		return ret;
>  
>  	dev->private = xive;
> +	kvm->arch.xive = xive;
>  	return 0;
>  }
>  
>