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Subject[PATCH 07/23] x86/fpu: Add basic helpers for dynamically enabled features
Date
From: Thomas Gleixner <tglx@linutronix.de>

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>
---
Changes from the tglx tree:
* Add the missing #ifdeffery. (Dave Hansen)
---
arch/x86/include/asm/fpu/xstate.h | 14 ++++++++++++++
arch/x86/kernel/fpu/core.c | 4 ++++
2 files changed, 18 insertions(+)

diff --git a/arch/x86/include/asm/fpu/xstate.h b/arch/x86/include/asm/fpu/xstate.h
index 43ae89d4bcd2..023000e79348 100644
--- a/arch/x86/include/asm/fpu/xstate.h
+++ b/arch/x86/include/asm/fpu/xstate.h
@@ -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 +99,15 @@ 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
+
+static __always_inline __pure bool fpu_state_size_dynamic(void)
+{
+ if (IS_ENABLED(CONFIG_X86_64))
+ return static_branch_unlikely(&__fpu_state_size_dynamic);
+ return false;
+}
+
#endif
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index eb911c843386..ff7d239fe961 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -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;
--
2.17.1
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