x86/fpu: Provide struct fpu_config

Provide a struct to store information about the maximum supported and the
default feature set and buffer sizes for both user and kernel space.

This allows quick retrieval of this information for the upcoming support
for dynamically enabled features.

 [ bp: Add vertical spacing between the struct members. ]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211014230739.126107370@linutronix.de

arch/x86/include/asm/fpu/types.h

@@ -378,4 +378,46 @@ struct fpu {
 	 */
 };
 
+/*
+ * FPU state configuration data. Initialized at boot time. Read only after init.
+ */
+struct fpu_state_config {
+	/*
+	 * @max_size:
+	 *
+	 * The maximum size of the register state buffer. Includes all
+	 * supported features except independent managed features.
+	 */
+	unsigned int		max_size;
+
+	/*
+	 * @default_size:
+	 *
+	 * The default size of the register state buffer. Includes all
+	 * supported features except independent managed features and
+	 * features which have to be requested by user space before usage.
+	 */
+	unsigned int		default_size;
+
+	/*
+	 * @max_features:
+	 *
+	 * The maximum supported features bitmap. Does not include
+	 * independent managed features.
+	 */
+	u64 max_features;
+
+	/*
+	 * @default_features:
+	 *
+	 * The default supported features bitmap. Does not include
+	 * independent managed features and features which have to
+	 * be requested by user space before usage.
+	 */
+	u64 default_features;
+};
+
+/* FPU state configuration information */
+extern struct fpu_state_config fpu_kernel_cfg, fpu_user_cfg;
+
 #endif /* _ASM_X86_FPU_H */

arch/x86/kernel/fpu/core.c

@@ -25,6 +25,10 @@
 #define CREATE_TRACE_POINTS
 #include <asm/trace/fpu.h>
 
+/* 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;
+
 /*
  * Represents the initial FPU state. It's mostly (but not completely) zeroes,
  * depending on the FPU hardware format: