Re: [PATCH v8 03/27] x86/fpu/xstate: Change names to separate XSAVES system and user states

Borislav Petkov
2019-08-21T14:45:37Z

On Tue, Aug 13, 2019 at 01:52:01PM -0700, Yu-cheng Yu wrote:
> Control-flow Enforcement (CET) MSR contents are XSAVES system states.
> To support CET, introduce XSAVES system states first.
>
> XSAVES is a "supervisor" instruction and, comparing to XSAVE, saves
> additional "supervisor" states that can be modified only from CPL 0.
> However, these states are per-task and not kernel's own. Rename
> "supervisor" states to "system" states to clearly separate them from
> "user" states.
>
> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
> ---
> arch/x86/include/asm/fpu/internal.h | 4 +-
> arch/x86/include/asm/fpu/xstate.h | 20 +++----
> arch/x86/kernel/fpu/init.c | 2 +-
> arch/x86/kernel/fpu/signal.c | 10 ++--
> arch/x86/kernel/fpu/xstate.c | 86 ++++++++++++++---------------
> 5 files changed, 60 insertions(+), 62 deletions(-)

...

> diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
> index e5cb67d67c03..d560e8861a3c 100644
> --- a/arch/x86/kernel/fpu/xstate.c
> +++ b/arch/x86/kernel/fpu/xstate.c
> @@ -54,13 +54,16 @@ static short xsave_cpuid_features[] __initdata = {
> };
>
> /*
> - * Mask of xstate features supported by the CPU and the kernel:
> + * XSAVES system states can only be modified from CPL 0 and saved by
> + * XSAVES. The rest are user states. The following is a mask of
> + * supported user state features derived from boot_cpu_has() and

...derived from detected CPUID feature flags and
SUPPORTED_XFEATURES_MASK.

--
Regards/Gruss,
Boris.

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