Re: [Xen-devel] [PATCH 2/3] tools/libxencalls: add new function to query hypercall buffer safety

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 15.06.18 at 15:26, <jgross@xxxxxxxx> wrote:
> Add a new function to query whether hypercall buffers are always safe
> to access by the hypervisor or might result in EFAULT.
> 
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> ---
>  tools/libs/call/Makefile          | 2 +-
>  tools/libs/call/freebsd.c         | 5 +++++
>  tools/libs/call/include/xencall.h | 7 +++++++
>  tools/libs/call/libxencall.map    | 5 +++++
>  tools/libs/call/linux.c           | 5 +++++
>  tools/libs/call/minios.c          | 5 +++++
>  tools/libs/call/netbsd.c          | 5 +++++
>  tools/libs/call/solaris.c         | 5 +++++
>  8 files changed, 38 insertions(+), 1 deletion(-)

Did you verify all of them to indeed be safe? If not, wouldn't it be better to
default to unsafe?

For Linux, is there perhaps a way to figure out whether the problem
features don't exist (or are disabled) in the kernel, so that (especially
on older kernels, where the privcmd driver surely is an old one) you
don't needlessly do the retries?

Jan



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