Subject: Re: [PATCH 4.3 090/125] KVM: s390: fix wrong lookup of VCPUs by array
 index
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-kernel@vger.kernel.org
References: <20151207145752.225938417@linuxfoundation.org>
 <20151207145756.688439386@linuxfoundation.org>
Cc: stable@vger.kernel.org, David Hildenbrand <dahi@linux.vnet.ibm.com>
From: Christian Borntraeger <borntraeger@de.ibm.com>
Message-ID: <566603CE.8040306@de.ibm.com>
Date: Mon, 7 Dec 2015 23:10:22 +0100
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On 12/07/2015 04:01 PM, Greg Kroah-Hartman wrote:
> 4.3-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: David Hildenbrand <dahi@linux.vnet.ibm.com>
> 
> commit 152e9f65d66f0a3891efc3869440becc0e7ff53f upstream.

Greg,

That commit has a dependency, the patch description has
Cc: stable@vger.kernel.org # db27a7a KVM: Provide function for VCPU lookup b
but db27a7a is not in 4.1 4.2 and 4.3 stable queue

Without that commit 4.1, 4.2 and 4.3 fail to build

Is the syntax for a dependency wrong?


> 
> For now, VCPUs were always created sequentially with incrementing
> VCPU ids. Therefore, the index in the VCPUs array matched the id.
> 
> As sequential creation might change with cpu hotplug, let's use
> the correct lookup function to find a VCPU by id, not array index.
> 
> Let's also use kvm_lookup_vcpu() for validation of the sending VCPU
> on external call injection.
> 
> Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
> Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> 
> ---
>  arch/s390/kvm/interrupt.c |    3 +--
>  arch/s390/kvm/sigp.c      |    8 ++------
>  2 files changed, 3 insertions(+), 8 deletions(-)
> 
> --- a/arch/s390/kvm/interrupt.c
> +++ b/arch/s390/kvm/interrupt.c
> @@ -1057,8 +1057,7 @@ static int __inject_extcall(struct kvm_v
>  				   src_id, 0);
> 
>  	/* sending vcpu invalid */
> -	if (src_id >= KVM_MAX_VCPUS ||
> -	    kvm_get_vcpu(vcpu->kvm, src_id) == NULL)
> +	if (kvm_get_vcpu_by_id(vcpu->kvm, src_id) == NULL)
>  		return -EINVAL;
> 
>  	if (sclp.has_sigpif)
> --- a/arch/s390/kvm/sigp.c
> +++ b/arch/s390/kvm/sigp.c
> @@ -291,12 +291,8 @@ static int handle_sigp_dst(struct kvm_vc
>  			   u16 cpu_addr, u32 parameter, u64 *status_reg)
>  {
>  	int rc;
> -	struct kvm_vcpu *dst_vcpu;
> +	struct kvm_vcpu *dst_vcpu = kvm_get_vcpu_by_id(vcpu->kvm, cpu_addr);
> 
> -	if (cpu_addr >= KVM_MAX_VCPUS)
> -		return SIGP_CC_NOT_OPERATIONAL;
> -
> -	dst_vcpu = kvm_get_vcpu(vcpu->kvm, cpu_addr);
>  	if (!dst_vcpu)
>  		return SIGP_CC_NOT_OPERATIONAL;
> 
> @@ -478,7 +474,7 @@ int kvm_s390_handle_sigp_pei(struct kvm_
>  	trace_kvm_s390_handle_sigp_pei(vcpu, order_code, cpu_addr);
> 
>  	if (order_code == SIGP_EXTERNAL_CALL) {
> -		dest_vcpu = kvm_get_vcpu(vcpu->kvm, cpu_addr);
> +		dest_vcpu = kvm_get_vcpu_by_id(vcpu->kvm, cpu_addr);
>  		BUG_ON(dest_vcpu == NULL);
> 
>  		kvm_s390_vcpu_wakeup(dest_vcpu);
> 
> 

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