Re: [Xen-devel] [PATCH V5 08/12] xen/vm_event: Check for VM_EVENT_FLAG_DUMMY only in Debug builds

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 13/02/15 16:33, Tamas K Lengyel wrote:
> The flag is only used for debugging purposes, thus it should be only checked
> for in debug builds of Xen.
>
> Signed-off-by: Tamas K Lengyel <tamas.lengyel@xxxxxxxxxxxx>

What is the purpose of the dummy flag?  I would have thought it would be
more dangerous to accidentally process a dummy response in a non-debug Xen.

~Andrew

> ---
>  xen/arch/x86/mm/mem_sharing.c | 2 ++
>  xen/arch/x86/mm/p2m.c         | 2 ++
>  xen/common/mem_access.c       | 2 ++
>  3 files changed, 6 insertions(+)
>
> diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c
> index 4e5477a..0459544 100644
> --- a/xen/arch/x86/mm/mem_sharing.c
> +++ b/xen/arch/x86/mm/mem_sharing.c
> @@ -606,8 +606,10 @@ int mem_sharing_sharing_resume(struct domain *d)
>              continue;
>          }
>  
> +#ifndef NDEBUG
>          if ( rsp.flags & VM_EVENT_FLAG_DUMMY )
>              continue;
> +#endif
>  
>          /* Validate the vcpu_id in the response. */
>          if ( (rsp.vcpu_id >= d->max_vcpus) || !d->vcpu[rsp.vcpu_id] )
> diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
> index 5ce852e..68d57d7 100644
> --- a/xen/arch/x86/mm/p2m.c
> +++ b/xen/arch/x86/mm/p2m.c
> @@ -1312,8 +1312,10 @@ void p2m_mem_paging_resume(struct domain *d)
>              continue;
>          }
>  
> +#ifndef NDEBUG
>          if ( rsp.flags & VM_EVENT_FLAG_DUMMY )
>              continue;
> +#endif
>  
>          /* Validate the vcpu_id in the response. */
>          if ( (rsp.vcpu_id >= d->max_vcpus) || !d->vcpu[rsp.vcpu_id] )
> diff --git a/xen/common/mem_access.c b/xen/common/mem_access.c
> index a6d82d1..63f2b52 100644
> --- a/xen/common/mem_access.c
> +++ b/xen/common/mem_access.c
> @@ -44,8 +44,10 @@ void mem_access_resume(struct domain *d)
>              continue;
>          }
>  
> +#ifndef NDEBUG
>          if ( rsp.flags & VM_EVENT_FLAG_DUMMY )
>              continue;
> +#endif
>  
>          /* Validate the vcpu_id in the response. */
>          if ( (rsp.vcpu_id >= d->max_vcpus) || !d->vcpu[rsp.vcpu_id] )


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