This summary will help to guide the proper use of the enabling model. Signed-off-by: Chang S. Bae <chang.seok.bae@xxxxxxxxx> Reviewed-by: Tony Luck <tony.luck@xxxxxxxxx> Cc: x86@xxxxxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx Cc: linux-doc@xxxxxxxxxxxxxxx --- Changes from v3: * Add as a new patch (Tony Luck). --- Documentation/x86/xstate.rst | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/Documentation/x86/xstate.rst b/Documentation/x86/xstate.rst index 5cec7fb558d6..2577b28ad942 100644 --- a/Documentation/x86/xstate.rst +++ b/Documentation/x86/xstate.rst @@ -11,6 +11,20 @@ are enabled by XCR0 as well, but the first use of related instruction is trapped by the kernel because by default the required large XSTATE buffers are not allocated automatically. +The purpose for dynamic features +-------------------------------- + + - Legacy userspace libraries have hard-coded sizes for an alternate signal + stack. With the arch_prctl() options, the signal frame beyond AVX-512 + and PKRU will not be written by old programs as they are prevented from + using dynamic features. Then, the small signal stack will be compatible + on systems that support dynamic features. + + - Modern server systems are consolidating more applications to share the + CPU resource. The risk of applications interfering with each other is + growing. The controllability on the resource trends to be more + warranted. Thus, this permission mechanism will be useful for that. + Using dynamically enabled XSTATE features in user space applications -------------------------------------------------------------------- -- 2.17.1
