x86/fpu: Calculate the default sizes independently

When dynamically enabled states are supported the maximum and default sizes
for the kernel buffers and user space interfaces are not longer identical.

Put the necessary calculations in place which only take the default enabled
features into account.

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/kernel/fpu/xstate.c

@@ -781,35 +781,40 @@ static bool __init is_supported_xstate_size(unsigned int test_xstate_size)
 static int __init init_xstate_size(void)
 {
 	/* Recompute the context size for enabled features: */
-	unsigned int user_size, kernel_size;
+	unsigned int user_size, kernel_size, kernel_default_size;
+	bool compacted = cpu_feature_enabled(X86_FEATURE_XSAVES);
 
 	/* Uncompacted user space size */
 	user_size = get_xsave_size_user();
 
 	/*
 	 * XSAVES kernel size includes supervisor states and
-	 * uses compacted format.
+	 * uses compacted format when available.
 	 *
 	 * XSAVE does not support supervisor states so
 	 * kernel and user size is identical.
 	 */
-	if (cpu_feature_enabled(X86_FEATURE_XSAVES))
+	if (compacted)
 		kernel_size = get_xsaves_size_no_independent();
 	else
 		kernel_size = user_size;
 
-	/* Ensure we have the space to store all enabled features. */
-	if (!is_supported_xstate_size(kernel_size))
+	kernel_default_size =
+		xstate_calculate_size(fpu_kernel_cfg.default_features, compacted);
+
+	/* Ensure we have the space to store all default enabled features. */
+	if (!is_supported_xstate_size(kernel_default_size))
 		return -EINVAL;
 
 	if (!paranoid_xstate_size_valid(kernel_size))
 		return -EINVAL;
 
-	/* Keep it the same for now */
 	fpu_kernel_cfg.max_size = kernel_size;
-	fpu_kernel_cfg.default_size = kernel_size;
 	fpu_user_cfg.max_size = user_size;
-	fpu_user_cfg.default_size = user_size;
+
+	fpu_kernel_cfg.default_size = kernel_default_size;
+	fpu_user_cfg.default_size =
+		xstate_calculate_size(fpu_user_cfg.default_features, false);
 
 	return 0;
 }
@@ -894,15 +899,21 @@ void __init fpu__init_system_xstate(unsigned int legacy_size)
 			fpu_kernel_cfg.max_features &= ~BIT_ULL(i);
 	}
 
+	if (!cpu_feature_enabled(X86_FEATURE_XFD))
+		fpu_kernel_cfg.max_features &= ~XFEATURE_MASK_USER_DYNAMIC;
+
 	fpu_kernel_cfg.max_features &= XFEATURE_MASK_USER_SUPPORTED |
 			      XFEATURE_MASK_SUPERVISOR_SUPPORTED;
 
 	fpu_user_cfg.max_features = fpu_kernel_cfg.max_features;
 	fpu_user_cfg.max_features &= XFEATURE_MASK_USER_SUPPORTED;
 
-	/* Identical for now */
+	/* Clean out dynamic features from default */
 	fpu_kernel_cfg.default_features = fpu_kernel_cfg.max_features;
+	fpu_kernel_cfg.default_features &= ~XFEATURE_MASK_USER_DYNAMIC;
+
 	fpu_user_cfg.default_features = fpu_user_cfg.max_features;
+	fpu_user_cfg.default_features &= ~XFEATURE_MASK_USER_DYNAMIC;
 
 	/* Store it for paranoia check at the end */
 	xfeatures = fpu_kernel_cfg.max_features;
@@ -913,6 +924,7 @@ void __init fpu__init_system_xstate(unsigned int legacy_size)
 	if (err)
 		goto out_disable;
 
+	/* Reset the state for the current task */
 	fpstate_reset(&current->thread.fpu);
 
 	/*