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x86/fpu: Add basic helpers for dynamically enabled features

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To allow building up the infrastructure required to support dynamically
enabled FPU features, add:

 - XFEATURES_MASK_DYNAMIC

   This constant will hold xfeatures which can be dynamically enabled.

 - fpu_state_size_dynamic()

   A static branch for 64-bit and a simple 'return false' for 32-bit.

   This helper allows to add dynamic-feature-specific changes to common
   code which is shared between 32-bit and 64-bit without #ifdeffery.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211021225527.10184-8-chang.seok.bae@intel.com
This commit is contained in:
Thomas Gleixner 2021-10-21 15:55:11 -07:00 committed by Borislav Petkov
parent db8268df09
commit 23686ef25d
2 changed files with 25 additions and 0 deletions
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21
arch/x86/include/asm/fpu/xstate.h
View File

@ -43,6 +43,9 @@
#define XFEATURE_MASK_USER_RESTORE \
(XFEATURE_MASK_USER_SUPPORTED & ~XFEATURE_MASK_PKRU)
/* Features which are dynamically enabled for a process on request */
#define XFEATURE_MASK_USER_DYNAMIC 0ULL
/* All currently supported supervisor features */
#define XFEATURE_MASK_SUPERVISOR_SUPPORTED (XFEATURE_MASK_PASID)
@ -96,4 +99,22 @@ int xfeature_size(int xfeature_nr);
void xsaves(struct xregs_state *xsave, u64 mask);
void xrstors(struct xregs_state *xsave, u64 mask);
#ifdef CONFIG_X86_64
DECLARE_STATIC_KEY_FALSE(__fpu_state_size_dynamic);
#endif
#ifdef CONFIG_X86_64
DECLARE_STATIC_KEY_FALSE(__fpu_state_size_dynamic);
static __always_inline __pure bool fpu_state_size_dynamic(void)
{
return static_branch_unlikely(&__fpu_state_size_dynamic);
}
#else
static __always_inline __pure bool fpu_state_size_dynamic(void)
{
return false;
}
#endif
#endif

4
arch/x86/kernel/fpu/core.c
View File

@ -25,6 +25,10 @@
#define CREATE_TRACE_POINTS
#include <asm/trace/fpu.h>
#ifdef CONFIG_X86_64
DEFINE_STATIC_KEY_FALSE(__fpu_state_size_dynamic);
#endif
/* The FPU state configuration data for kernel and user space */
struct fpu_state_config fpu_kernel_cfg __ro_after_init;
struct fpu_state_config fpu_user_cfg __ro_after_init;