[PATCH] KVM: arm/arm64: Fix vgic init race

[PATCH] KVM: arm/arm64: Fix vgic init race

[Christoffer Dall]

The vgic_init function can race with kvm_arch_vcpu_create() which does
not hold kvm_lock() and we therefore have no synchronization primitives
to ensure we're doing the right thing.

As the user is trying to initialize or run the VM while at the same time
creating more VCPUs, we just have to refuse to initialize the VGIC in
this case rather than silently failing with a broken VCPU.

Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>
---
 virt/kvm/arm/vgic/vgic-init.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
index 9406eaf..c0c0b88 100644
--- a/virt/kvm/arm/vgic/vgic-init.c
+++ b/virt/kvm/arm/vgic/vgic-init.c
@@ -286,6 +286,10 @@ int vgic_init(struct kvm *kvm)
        if (vgic_initialized(kvm))
                return 0;

+       /* Are we also in the middle of creating a VCPU? */
+       if (kvm->created_vcpus != atomic_read(&kvm->online_vcpus))
+               return -EBUSY;
+
        /* freeze the number of spis */
        if (!dist->nr_spis)
                dist->nr_spis = VGIC_NR_IRQS_LEGACY - VGIC_NR_PRIVATE_IRQS;
--
2.7.4

IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you.

[PATCH] KVM: arm/arm64: Fix vgic init race

[Christoffer Dall]

The vgic_init function can race with kvm_arch_vcpu_create() which does
not hold kvm_lock() and we therefore have no synchronization primitives
to ensure we're doing the right thing.

As the user is trying to initialize or run the VM while at the same time
creating more VCPUs, we just have to refuse to initialize the VGIC in
this case rather than silently failing with a broken VCPU.

Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>
---
 virt/kvm/arm/vgic/vgic-init.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
index 9406eaf..c0c0b88 100644
--- a/virt/kvm/arm/vgic/vgic-init.c
+++ b/virt/kvm/arm/vgic/vgic-init.c
@@ -286,6 +286,10 @@ int vgic_init(struct kvm *kvm)
        if (vgic_initialized(kvm))
                return 0;

+       /* Are we also in the middle of creating a VCPU? */
+       if (kvm->created_vcpus != atomic_read(&kvm->online_vcpus))
+               return -EBUSY;
+
        /* freeze the number of spis */
        if (!dist->nr_spis)
                dist->nr_spis = VGIC_NR_IRQS_LEGACY - VGIC_NR_PRIVATE_IRQS;
--
2.7.4

IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you.

Re: [PATCH] KVM: arm/arm64: Fix vgic init race

[Auger Eric]

Hi Christoffer,

On 07/03/2018 11:26 PM, Christoffer Dall wrote:
> The vgic_init function can race with kvm_arch_vcpu_create() which does
> not hold kvm_lock() and we therefore have no synchronization primitives
> to ensure we're doing the right thing.
> 
> As the user is trying to initialize or run the VM while at the same time
> creating more VCPUs, we just have to refuse to initialize the VGIC in
> this case rather than silently failing with a broken VCPU.
> 
> Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>

Thanks

Eric
> ---
>  virt/kvm/arm/vgic/vgic-init.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
> index 9406eaf..c0c0b88 100644
> --- a/virt/kvm/arm/vgic/vgic-init.c
> +++ b/virt/kvm/arm/vgic/vgic-init.c
> @@ -286,6 +286,10 @@ int vgic_init(struct kvm *kvm)
>         if (vgic_initialized(kvm))
>                 return 0;
> 
> +       /* Are we also in the middle of creating a VCPU? */
> +       if (kvm->created_vcpus != atomic_read(&kvm->online_vcpus))
> +               return -EBUSY;
> +
>         /* freeze the number of spis */
>         if (!dist->nr_spis)
>                 dist->nr_spis = VGIC_NR_IRQS_LEGACY - VGIC_NR_PRIVATE_IRQS;
> --
> 2.7.4
> 
> IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you.
> 

[PATCH] KVM: arm/arm64: Fix vgic init race

[Auger Eric]

Hi Christoffer,

On 07/03/2018 11:26 PM, Christoffer Dall wrote:
> The vgic_init function can race with kvm_arch_vcpu_create() which does
> not hold kvm_lock() and we therefore have no synchronization primitives
> to ensure we're doing the right thing.
> 
> As the user is trying to initialize or run the VM while at the same time
> creating more VCPUs, we just have to refuse to initialize the VGIC in
> this case rather than silently failing with a broken VCPU.
> 
> Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>

Thanks

Eric
> ---
>  virt/kvm/arm/vgic/vgic-init.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
> index 9406eaf..c0c0b88 100644
> --- a/virt/kvm/arm/vgic/vgic-init.c
> +++ b/virt/kvm/arm/vgic/vgic-init.c
> @@ -286,6 +286,10 @@ int vgic_init(struct kvm *kvm)
>         if (vgic_initialized(kvm))
>                 return 0;
> 
> +       /* Are we also in the middle of creating a VCPU? */
> +       if (kvm->created_vcpus != atomic_read(&kvm->online_vcpus))
> +               return -EBUSY;
> +
>         /* freeze the number of spis */
>         if (!dist->nr_spis)
>                 dist->nr_spis = VGIC_NR_IRQS_LEGACY - VGIC_NR_PRIVATE_IRQS;
> --
> 2.7.4
> 
> IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you.
> 

Re: [PATCH] KVM: arm/arm64: Fix vgic init race

[Marc Zyngier]

On 03/07/18 22:26, Christoffer Dall wrote:
> The vgic_init function can race with kvm_arch_vcpu_create() which does
> not hold kvm_lock() and we therefore have no synchronization primitives
> to ensure we're doing the right thing.
> 
> As the user is trying to initialize or run the VM while at the same time
> creating more VCPUs, we just have to refuse to initialize the VGIC in
> this case rather than silently failing with a broken VCPU.
> 
> Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>
> ---
>  virt/kvm/arm/vgic/vgic-init.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
> index 9406eaf..c0c0b88 100644
> --- a/virt/kvm/arm/vgic/vgic-init.c
> +++ b/virt/kvm/arm/vgic/vgic-init.c
> @@ -286,6 +286,10 @@ int vgic_init(struct kvm *kvm)
>  	if (vgic_initialized(kvm))
>  		return 0;
>  
> +	/* Are we also in the middle of creating a VCPU? */
> +	if (kvm->created_vcpus != atomic_read(&kvm->online_vcpus))
> +		return -EBUSY;
> +
>  	/* freeze the number of spis */
>  	if (!dist->nr_spis)
>  		dist->nr_spis = VGIC_NR_IRQS_LEGACY - VGIC_NR_PRIVATE_IRQS;
> 

Applied to queue.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...

[PATCH] KVM: arm/arm64: Fix vgic init race

[Marc Zyngier]

On 03/07/18 22:26, Christoffer Dall wrote:
> The vgic_init function can race with kvm_arch_vcpu_create() which does
> not hold kvm_lock() and we therefore have no synchronization primitives
> to ensure we're doing the right thing.
> 
> As the user is trying to initialize or run the VM while at the same time
> creating more VCPUs, we just have to refuse to initialize the VGIC in
> this case rather than silently failing with a broken VCPU.
> 
> Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>
> ---
>  virt/kvm/arm/vgic/vgic-init.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
> index 9406eaf..c0c0b88 100644
> --- a/virt/kvm/arm/vgic/vgic-init.c
> +++ b/virt/kvm/arm/vgic/vgic-init.c
> @@ -286,6 +286,10 @@ int vgic_init(struct kvm *kvm)
>  	if (vgic_initialized(kvm))
>  		return 0;
>  
> +	/* Are we also in the middle of creating a VCPU? */
> +	if (kvm->created_vcpus != atomic_read(&kvm->online_vcpus))
> +		return -EBUSY;
> +
>  	/* freeze the number of spis */
>  	if (!dist->nr_spis)
>  		dist->nr_spis = VGIC_NR_IRQS_LEGACY - VGIC_NR_PRIVATE_IRQS;
> 

Applied to queue.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...