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Date: Fri, 22 Oct 2021 19:56:30 -0000
From: "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...e.de>,
x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/fpu] x86/fpu/xstate: Cleanup size calculations
The following commit has been merged into the x86/fpu branch of tip:
Commit-ID: cd9ae761744912a96d7fd968b9c0173594e3f6be
Gitweb: https://git.kernel.org/tip/cd9ae761744912a96d7fd968b9c0173594e3f6be
Author: Thomas Gleixner <tglx@...utronix.de>
AuthorDate: Fri, 15 Oct 2021 01:09:32 +02:00
Committer: Borislav Petkov <bp@...e.de>
CommitterDate: Thu, 21 Oct 2021 19:37:53 +02:00
x86/fpu/xstate: Cleanup size calculations
The size calculations are partially unreadable gunk. Clean them up.
No functional change.
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Borislav Petkov <bp@...e.de>
Link: https://lkml.kernel.org/r/20211014230739.241223689@linutronix.de
---
arch/x86/kernel/fpu/xstate.c | 82 +++++++++++++++++++----------------
1 file changed, 46 insertions(+), 36 deletions(-)
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 4cfd3bc..c5582bd 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -527,7 +527,7 @@ static void __init __xstate_dump_leaves(void)
* that our software representation matches what the CPU
* tells us about the state's size.
*/
-static void __init check_xstate_against_struct(int nr)
+static bool __init check_xstate_against_struct(int nr)
{
/*
* Ask the CPU for the size of the state.
@@ -557,7 +557,9 @@ static void __init check_xstate_against_struct(int nr)
((nr >= XFEATURE_RSRVD_COMP_11) && (nr <= XFEATURE_LBR))) {
WARN_ONCE(1, "no structure for xstate: %d\n", nr);
XSTATE_WARN_ON(1);
+ return false;
}
+ return true;
}
/*
@@ -569,38 +571,44 @@ static void __init check_xstate_against_struct(int nr)
* covered by these checks. Only the size of the buffer for task->fpu
* is checked here.
*/
-static void __init do_extra_xstate_size_checks(void)
+static bool __init paranoid_xstate_size_valid(unsigned int kernel_size)
{
- int paranoid_xstate_size = FXSAVE_SIZE + XSAVE_HDR_SIZE;
+ bool compacted = cpu_feature_enabled(X86_FEATURE_XSAVES);
+ unsigned int size = FXSAVE_SIZE + XSAVE_HDR_SIZE;
int i;
for_each_extended_xfeature(i, xfeatures_mask_all) {
- check_xstate_against_struct(i);
+ if (!check_xstate_against_struct(i))
+ return false;
/*
* Supervisor state components can be managed only by
* XSAVES.
*/
- if (!cpu_feature_enabled(X86_FEATURE_XSAVES))
- XSTATE_WARN_ON(xfeature_is_supervisor(i));
+ if (!compacted && xfeature_is_supervisor(i)) {
+ XSTATE_WARN_ON(1);
+ return false;
+ }
/* Align from the end of the previous feature */
if (xfeature_is_aligned(i))
- paranoid_xstate_size = ALIGN(paranoid_xstate_size, 64);
+ size = ALIGN(size, 64);
/*
- * The offset of a given state in the non-compacted
- * format is given to us in a CPUID leaf. We check
- * them for being ordered (increasing offsets) in
- * setup_xstate_features(). XSAVES uses compacted format.
+ * In compacted format the enabled features are packed,
+ * i.e. disabled features do not occupy space.
+ *
+ * In non-compacted format the offsets are fixed and
+ * disabled states still occupy space in the memory buffer.
*/
- if (!cpu_feature_enabled(X86_FEATURE_XSAVES))
- paranoid_xstate_size = xfeature_uncompacted_offset(i);
+ if (!compacted)
+ size = xfeature_uncompacted_offset(i);
/*
- * The compacted-format offset always depends on where
- * the previous state ended.
+ * Add the feature size even for non-compacted format
+ * to make the end result correct
*/
- paranoid_xstate_size += xfeature_size(i);
+ size += xfeature_size(i);
}
- XSTATE_WARN_ON(paranoid_xstate_size != fpu_kernel_xstate_size);
+ XSTATE_WARN_ON(size != kernel_size);
+ return size == kernel_size;
}
/*
@@ -653,7 +661,7 @@ static unsigned int __init get_xsaves_size_no_independent(void)
return size;
}
-static unsigned int __init get_xsave_size(void)
+static unsigned int __init get_xsave_size_user(void)
{
unsigned int eax, ebx, ecx, edx;
/*
@@ -684,31 +692,33 @@ 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 possible_xstate_size;
- unsigned int xsave_size;
+ unsigned int user_size, kernel_size;
- xsave_size = get_xsave_size();
+ /* Uncompacted user space size */
+ user_size = get_xsave_size_user();
- if (boot_cpu_has(X86_FEATURE_XSAVES))
- possible_xstate_size = get_xsaves_size_no_independent();
+ /*
+ * XSAVES kernel size includes supervisor states and
+ * uses compacted format.
+ *
+ * XSAVE does not support supervisor states so
+ * kernel and user size is identical.
+ */
+ if (cpu_feature_enabled(X86_FEATURE_XSAVES))
+ kernel_size = get_xsaves_size_no_independent();
else
- possible_xstate_size = xsave_size;
+ kernel_size = user_size;
- /* Ensure we have the space to store all enabled: */
- if (!is_supported_xstate_size(possible_xstate_size))
+ /* Ensure we have the space to store all enabled features. */
+ if (!is_supported_xstate_size(kernel_size))
return -EINVAL;
- /*
- * The size is OK, we are definitely going to use xsave,
- * make it known to the world that we need more space.
- */
- fpu_kernel_xstate_size = possible_xstate_size;
- do_extra_xstate_size_checks();
+ if (!paranoid_xstate_size_valid(kernel_size))
+ return -EINVAL;
+
+ fpu_kernel_xstate_size = kernel_size;
+ fpu_user_xstate_size = user_size;
- /*
- * User space is always in standard format.
- */
- fpu_user_xstate_size = xsave_size;
return 0;
}
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