[PATCH v9 07/27] x86/fpu/xstate: Warn if kernel dynamic xfeatures detected in normal fpstate

Yang Weijiang
2024-01-24T02:42:37Z

Kernel dynamic xfeatures now are __ONLY__ enabled for guest fpstate, i.e.,
never for normal kernel fpstate. The bits are added when guest FPU config
is initialized. Guest fpstate is allocated with fpstate->is_guest set to
%true.

For normal fpstate, the bits should have been removed when initializes
kernel FPU config settings, WARN_ONCE() if kernel detects normal fpstate
xfeatures contains kernel dynamic xfeatures before executes xsaves.

Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
---
arch/x86/kernel/fpu/xstate.h | 3 +++
1 file changed, 3 insertions(+)

diff --git a/arch/x86/kernel/fpu/xstate.h b/arch/x86/kernel/fpu/xstate.h
index 3518fb26d06b..83ebf1e1cbb4 100644
--- a/arch/x86/kernel/fpu/xstate.h
+++ b/arch/x86/kernel/fpu/xstate.h
@@ -185,6 +185,9 @@ static inline void os_xsave(struct fpstate *fpstate)
WARN_ON_FPU(!alternatives_patched);
xfd_validate_state(fpstate, mask, false);

+ WARN_ON_FPU(!fpstate->is_guest &&
+ (mask & XFEATURE_MASK_KERNEL_DYNAMIC));
+
XSTATE_XSAVE(&fpstate->regs.xsave, lmask, hmask, err);

/* We should never fault when copying to a kernel buffer: */
--
2.39.3