linux-kernel - [tip: x86/fpu] x86/fpu: Calculate the default sizes independently

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Message-ID: <163526499487.626.4563266865851615075.tip-bot2@tip-bot2>
Date:   Tue, 26 Oct 2021 16:16:34 -0000
From:   "tip-bot2 for Chang S. Bae" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Chang S. Bae" <chang.seok.bae@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...e.de>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: x86/fpu] x86/fpu: Calculate the default sizes independently

The following commit has been merged into the x86/fpu branch of tip:

Commit-ID:     2ae996e0c1a38ca57a52438ab9deec6761dcba62
Gitweb:        https://git.kernel.org/tip/2ae996e0c1a38ca57a52438ab9deec6761dcba62
Author:        Chang S. Bae <chang.seok.bae@...el.com>
AuthorDate:    Thu, 21 Oct 2021 15:55:25 -07:00
Committer:     Borislav Petkov <bp@...e.de>
CommitterDate: Tue, 26 Oct 2021 10:53:02 +02:00

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 <chang.seok.bae@...el.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Borislav Petkov <bp@...e.de>
Link: https://lore.kernel.org/r/20211021225527.10184-22-chang.seok.bae@intel.com
---
 arch/x86/kernel/fpu/xstate.c | 30 +++++++++++++++++++++---------
 1 file changed, 21 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 3372da8..b0f6e9a 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/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);
 
 	/*