Re: [Xen-devel] [PATCH 04/17] vmx: nest: domain and vcpu flags

[Tim Deegan <Tim.Deegan@xxxxxxxxxx>]

At 10:41 +0100 on 22 Apr (1271932876), Qing He wrote:
> Introduce a domain create flag to allow user to set availability
> of nested virtualization.
> The flag will be used to disable all reporting and function
> facilities, improving guest security.

I have the same reservation about this as Christoph's patch: I don't
think this needs to be a create-time flag - there's no reason it can't
be enabled or disabled with a domctl after domain creation.  (And of
course we'll want it to bve the same interface on both SVM and VMX.)

Tim.

> Another per vcpu flag is used to indicate whether the vcpu
> is in L1 or L2 context.
> 
> Signed-off-by: Qing He <qing.he@xxxxxxxxx>
> 
> ---
>  arch/x86/domain.c            |    4 ++++
>  common/domctl.c              |    5 ++++-
>  include/asm-x86/hvm/domain.h |    1 +
>  include/asm-x86/hvm/vcpu.h   |    2 ++
>  include/public/domctl.h      |    3 +++
>  include/xen/sched.h          |    3 +++
>  6 files changed, 17 insertions(+), 1 deletion(-)
> 
> diff -r a0bbec37b529 -r 6f0f41f80285 xen/arch/x86/domain.c
> --- a/xen/arch/x86/domain.c   Thu Apr 22 21:49:38 2010 +0800
> +++ b/xen/arch/x86/domain.c   Thu Apr 22 22:30:00 2010 +0800
> @@ -413,6 +413,10 @@
>  
>      d->arch.s3_integrity = !!(domcr_flags & DOMCRF_s3_integrity);
>  
> +    d->arch.hvm_domain.nesting_avail =
> +        is_hvm_domain(d) &&
> +        (domcr_flags & DOMCRF_nesting);
> +
>      INIT_LIST_HEAD(&d->arch.pdev_list);
>  
>      d->arch.relmem = RELMEM_not_started;
> diff -r a0bbec37b529 -r 6f0f41f80285 xen/common/domctl.c
> --- a/xen/common/domctl.c     Thu Apr 22 21:49:38 2010 +0800
> +++ b/xen/common/domctl.c     Thu Apr 22 22:30:00 2010 +0800
> @@ -393,7 +393,8 @@
>          if ( supervisor_mode_kernel ||
>               (op->u.createdomain.flags &
>               ~(XEN_DOMCTL_CDF_hvm_guest | XEN_DOMCTL_CDF_hap |
> -               XEN_DOMCTL_CDF_s3_integrity | XEN_DOMCTL_CDF_oos_off)) )
> +               XEN_DOMCTL_CDF_s3_integrity | XEN_DOMCTL_CDF_oos_off |
> +               XEN_DOMCTL_CDF_nesting)) )
>              break;
>  
>          dom = op->domain;
> @@ -429,6 +430,8 @@
>              domcr_flags |= DOMCRF_s3_integrity;
>          if ( op->u.createdomain.flags & XEN_DOMCTL_CDF_oos_off )
>              domcr_flags |= DOMCRF_oos_off;
> +        if ( op->u.createdomain.flags & XEN_DOMCTL_CDF_nesting )
> +            domcr_flags |= DOMCRF_nesting;
>  
>          ret = -ENOMEM;
>          d = domain_create(dom, domcr_flags, op->u.createdomain.ssidref);
> diff -r a0bbec37b529 -r 6f0f41f80285 xen/include/asm-x86/hvm/domain.h
> --- a/xen/include/asm-x86/hvm/domain.h        Thu Apr 22 21:49:38 2010 +0800
> +++ b/xen/include/asm-x86/hvm/domain.h        Thu Apr 22 22:30:00 2010 +0800
> @@ -93,6 +93,7 @@
>      bool_t                 mem_sharing_enabled;
>      bool_t                 qemu_mapcache_invalidate;
>      bool_t                 is_s3_suspended;
> +    bool_t                 nesting_avail;
>  
>      union {
>          struct vmx_domain vmx;
> diff -r a0bbec37b529 -r 6f0f41f80285 xen/include/asm-x86/hvm/vcpu.h
> --- a/xen/include/asm-x86/hvm/vcpu.h  Thu Apr 22 21:49:38 2010 +0800
> +++ b/xen/include/asm-x86/hvm/vcpu.h  Thu Apr 22 22:30:00 2010 +0800
> @@ -70,6 +70,8 @@
>      bool_t              debug_state_latch;
>      bool_t              single_step;
>  
> +    bool_t              in_nesting;
> +
>      u64                 asid_generation;
>      u32                 asid;
>  
> diff -r a0bbec37b529 -r 6f0f41f80285 xen/include/public/domctl.h
> --- a/xen/include/public/domctl.h     Thu Apr 22 21:49:38 2010 +0800
> +++ b/xen/include/public/domctl.h     Thu Apr 22 22:30:00 2010 +0800
> @@ -64,6 +64,9 @@
>   /* Disable out-of-sync shadow page tables? */
>  #define _XEN_DOMCTL_CDF_oos_off       3
>  #define XEN_DOMCTL_CDF_oos_off        (1U<<_XEN_DOMCTL_CDF_oos_off)
> + /* Is nested virtualization allowed */
> +#define _XEN_DOMCTL_CDF_nesting       4
> +#define XEN_DOMCTL_CDF_nesting        (1U<<_XEN_DOMCTL_CDF_nesting)
>  };
>  typedef struct xen_domctl_createdomain xen_domctl_createdomain_t;
>  DEFINE_XEN_GUEST_HANDLE(xen_domctl_createdomain_t);
> diff -r a0bbec37b529 -r 6f0f41f80285 xen/include/xen/sched.h
> --- a/xen/include/xen/sched.h Thu Apr 22 21:49:38 2010 +0800
> +++ b/xen/include/xen/sched.h Thu Apr 22 22:30:00 2010 +0800
> @@ -393,6 +393,9 @@
>   /* DOMCRF_oos_off: dont use out-of-sync optimization for shadow page tables 
> */
>  #define _DOMCRF_oos_off         4
>  #define DOMCRF_oos_off          (1U<<_DOMCRF_oos_off)
> + /* DOMCRF_nesting: Create a domain that allows nested virtualization . */
> +#define _DOMCRF_nesting       5
> +#define DOMCRF_nesting        (1U<<_DOMCRF_nesting)
>  
>  /*
>   * rcu_lock_domain_by_id() is more efficient than get_domain_by_id().
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-devel

-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, XenServer Engineering
Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)

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