Re: [Xen-devel] [PATCH v5.1 2/8] xen: restrict: use xentoolcore_restrict_all

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Fri, 20 Oct 2017, Ian Jackson wrote:
> And insist that it works.
> 
> Drop individual use of xendevicemodel_restrict and
> xenforeignmemory_restrict.  These are not actually effective in this
> version of qemu, because qemu has a large number of fds open onto
> various Xen control devices.
> 
> The restriction arrangements are still not right, because the
> restriction needs to be done very late - after qemu has opened all of
> its control fds.
> 
> xentoolcore_restrict_all and xentoolcore.h are available in Xen 4.10
> and later, only.  Provide a compatibility stub.  And drop the
> compatibility stubs for the old functions.
> 
> Signed-off-by: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
> Reviewed-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
> ---
> v2: Modify the compatibility code, too.
>     Bump this patch ahead of "defer call to xen_restrict until running"
>     Retain call to xentoolcore_restrict_all
> ---
>  include/hw/xen/xen_common.h | 46 
> +++++++++++----------------------------------
>  1 file changed, 11 insertions(+), 35 deletions(-)
> 
> diff --git a/include/hw/xen/xen_common.h b/include/hw/xen/xen_common.h
> index 86c7f26..3f44a63 100644
> --- a/include/hw/xen/xen_common.h
> +++ b/include/hw/xen/xen_common.h
> @@ -91,6 +91,16 @@ static inline void 
> *xenforeignmemory_map2(xenforeignmemory_handle *h,
>      return xenforeignmemory_map(h, dom, prot, pages, arr, err);
>  }
>  
> +static inline int xentoolcore_restrict_all(domid_t domid)
> +{
> +    errno = ENOTTY;
> +    return -1;

Wait, if the compat stub returns error, and this patch removed the code
to check for ENOTTY, doesn't it prevent any QEMU compiled against older
Xen from working?

Or am I missing something?


> +}
> +
> +#else /* CONFIG_XEN_CTRL_INTERFACE_VERSION >= 41000 */
> +
> +#include <xentoolcore.h>
> +
>  #endif
>  
>  #if CONFIG_XEN_CTRL_INTERFACE_VERSION < 40900
> @@ -218,20 +228,6 @@ static inline int xendevicemodel_set_mem_type(
>      return xc_hvm_set_mem_type(dmod, domid, mem_type, first_pfn, nr);
>  }
>  
> -static inline int xendevicemodel_restrict(
> -    xendevicemodel_handle *dmod, domid_t domid)
> -{
> -    errno = ENOTTY;
> -    return -1;
> -}
> -
> -static inline int xenforeignmemory_restrict(
> -    xenforeignmemory_handle *fmem, domid_t domid)
> -{
> -    errno = ENOTTY;
> -    return -1;
> -}
> -
>  #else /* CONFIG_XEN_CTRL_INTERFACE_VERSION >= 40900 */
>  
>  #undef XC_WANT_COMPAT_DEVICEMODEL_API
> @@ -290,28 +286,8 @@ static inline int xen_modified_memory(domid_t domid, 
> uint64_t first_pfn,
>  static inline int xen_restrict(domid_t domid)
>  {
>      int rc;
> -
> -    /* Attempt to restrict devicemodel operations */
> -    rc = xendevicemodel_restrict(xen_dmod, domid);
> +    rc = xentoolcore_restrict_all(domid);
>      trace_xen_domid_restrict(rc ? errno : 0);
> -
> -    if (rc < 0) {
> -        /*
> -         * If errno is ENOTTY then restriction is not implemented so
> -         * there's no point in trying to restrict other types of
> -         * operation, but it should not be treated as a failure.
> -         */
> -        if (errno == ENOTTY) {
> -            return 0;
> -        }
> -
> -        return rc;
> -    }
> -
> -    /* Restrict foreignmemory operations */
> -    rc = xenforeignmemory_restrict(xen_fmem, domid);
> -    trace_xen_domid_restrict(rc ? errno : 0);
> -
>      return rc;
>  }
>  
> -- 
> 2.1.4
> 

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