x86/fpu/amx: Enable the AMX feature in 64-bit mode

Add the AMX state components in XFEATURE_MASK_USER_SUPPORTED and the
TILE_DATA component to the dynamic states and update the permission check
table accordingly.

This is only effective on 64 bit kernels as for 32bit kernels
XFEATURE_MASK_TILE is defined as 0.

TILE_DATA is caller-saved state and the only dynamic state. Add build time
sanity check to ensure the assumption that every dynamic feature is caller-
saved.

Make AMX state depend on XFD as it is dynamic feature.

Signed-off-by: Chang S. Bae <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: ChangSeokBae

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

@@ -35,7 +35,8 @@
 				      XFEATURE_MASK_Hi16_ZMM	 | \
 				      XFEATURE_MASK_PKRU | \
 				      XFEATURE_MASK_BNDREGS | \
-				      XFEATURE_MASK_BNDCSR)
+				      XFEATURE_MASK_BNDCSR | \
+				      XFEATURE_MASK_XTILE)
 
 /*
  * Features which are restored when returning to user space.
@@ -46,7 +47,7 @@
 	(XFEATURE_MASK_USER_SUPPORTED & ~XFEATURE_MASK_PKRU)
 
 /* Features which are dynamically enabled for a process on request */
-#define XFEATURE_MASK_USER_DYNAMIC	0ULL
+#define XFEATURE_MASK_USER_DYNAMIC	XFEATURE_MASK_XTILE_DATA
 
 /* All currently supported supervisor features */
 #define XFEATURE_MASK_SUPERVISOR_SUPPORTED (XFEATURE_MASK_PASID)

arch/x86/kernel/cpu/cpuid-deps.c

@@ -76,6 +76,7 @@ static const struct cpuid_dep cpuid_deps[] = {
 	{ X86_FEATURE_SGX1,			X86_FEATURE_SGX       },
 	{ X86_FEATURE_SGX2,			X86_FEATURE_SGX1      },
 	{ X86_FEATURE_XFD,			X86_FEATURE_XSAVES    },
+	{ X86_FEATURE_AMX_TILE,			X86_FEATURE_XFD       },
 	{}
 };
 

arch/x86/kernel/fpu/core.c

@@ -494,6 +494,12 @@ int fpu_clone(struct task_struct *dst, unsigned long clone_flags)
 		return 0;
 	}
 
+	/*
+	 * If a new feature is added, ensure all dynamic features are
+	 * caller-saved from here!
+	 */
+	BUILD_BUG_ON(XFEATURE_MASK_USER_DYNAMIC != XFEATURE_MASK_XTILE_DATA);
+
 	/*
 	 * Save the default portion of the current FPU state into the
 	 * clone. Assume all dynamic features to be defined as caller-

arch/x86/kernel/fpu/xstate.c

@@ -404,7 +404,8 @@ static __init void os_xrstor_booting(struct xregs_state *xstate)
 	 XFEATURE_MASK_PKRU |			\
 	 XFEATURE_MASK_BNDREGS |		\
 	 XFEATURE_MASK_BNDCSR |			\
-	 XFEATURE_MASK_PASID)
+	 XFEATURE_MASK_PASID |			\
+	 XFEATURE_MASK_XTILE)
 
 /*
  * setup the xstate image representing the init state
@@ -1636,7 +1637,7 @@ static int __xstate_request_perm(u64 permitted, u64 requested)
  * Permissions array to map facilities with more than one component
  */
 static const u64 xstate_prctl_req[XFEATURE_MAX] = {
-	/* [XFEATURE_XTILE_DATA] = XFEATURE_MASK_XTILE, */
+	[XFEATURE_XTILE_DATA] = XFEATURE_MASK_XTILE_DATA,
 };
 
 static int xstate_request_perm(unsigned long idx)