Re: [PATCH v2 03/39] x86/cpufeatures: Add CPU feature flags for shadow stacks

On Fri, 2022-10-14 at 18:20 +0200, Borislav Petkov wrote:

On Thu, Sep 29, 2022 at 03:29:00PM -0700, Rick Edgecombe wrote:

quoted

From: Yu-cheng Yu <redacted>

The Control-Flow Enforcement Technology contains two related
features,
one of which is Shadow Stacks. Future patches will utilize this
feature
for shadow stack support in KVM, so add a CPU feature flags for
Shadow
Stacks (CPUID.(EAX=7,ECX=0):ECX[bit 7]).

To protect shadow stack state from malicious modification, the
registers
are only accessible in supervisor mode. This implementation
context-switches the registers with XSAVES. Make X86_FEATURE_SHSTK
depend
on XSAVES.

Signed-off-by: Yu-cheng Yu <redacted>
Co-developed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: Kees Cook <redacted>

Reviewed-by: Borislav Petkov <redacted>

Thanks!