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From: "Chang S. Bae" <chang.seok.bae@intel.com>
To: bp@suse.de, luto@kernel.org, tglx@linutronix.de,
	mingo@kernel.org, x86@kernel.org
Cc: len.brown@intel.com, dave.hansen@intel.com, jing2.liu@intel.com,
	ravi.v.shankar@intel.com, linux-kernel@vger.kernel.org,
	chang.seok.bae@intel.com
Subject: [PATCH v6-fix 06/26] x86/fpu/xstate: Calculate and remember dynamic XSTATE buffer sizes
Date: Fri,  2 Jul 2021 08:17:26 -0700	[thread overview]
Message-ID: <20210702151726.27293-1-chang.seok.bae@intel.com> (raw)
In-Reply-To: <7B6BF36A-E1C5-4D7C-96EC-2036AE27414B@intel.com>

The XSTATE per-task buffer is currently embedded into struct fpu with
static size. To accommodate dynamic user XSTATEs, record the maximum and
minimum buffer sizes.

Rename the size calculation function. It calculates the maximum XSTATE size
and sanity checks it with CPUID. It also calculates the static embedded
buffer size by excluding the dynamic user states from the maximum size.

Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Reviewed-by: Len Brown <len.brown@intel.com>
Cc: x86@kernel.org
Cc: linux-kernel@vger.kernel.org
---
Changes from v6:
* Fixed the v6 changes.

Changes from v5:
* Re-adjusted some local variable names.

Changes from v4:
* Massaged the function description, in preparation for the change
  with a return value.

Changes from v3:
* Updated the changelog. (Borislav Petkov)
* Updated the code comment. (Borislav Petkov)
* Adjusted the calculation function naming.
* Moved out the new variable addition into a new patch.

Changes from v2:
* Updated the changelog with task->fpu removed. (Borislav Petkov)
* Renamed the in-line size variable.
* Updated some code comments.
---
 arch/x86/kernel/fpu/xstate.c | 59 ++++++++++++++++++++++++------------
 1 file changed, 40 insertions(+), 19 deletions(-)

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index e03853bb2603..75969f1ef4b3 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -590,24 +590,36 @@ static void check_xstate_against_struct(int nr)
 	}
 }
 
-/*
- * This essentially double-checks what the cpu told us about
- * how large the XSAVE buffer needs to be.  We are recalculating
- * it to be safe.
+/**
+ * calculate_xstate_sizes() - Calculate the xstate per-task buffer sizes.
+ *
+ * Record the minimum and double-check the maximum against what the CPU
+ * told.
  *
  * Independent XSAVE features allocate their own buffers and are not
  * covered by these checks. Only the size of the buffer for task->fpu
  * is checked here.
+ *
+ * Dynamic user states are stored in this per-task buffer. They account
+ * for the delta between the maximum and the minimum.
+ *
+ * Return: nothing.
  */
-static void do_extra_xstate_size_checks(void)
+static void calculate_xstate_sizes(void)
 {
-	int paranoid_xstate_size = FXSAVE_SIZE + XSAVE_HDR_SIZE;
-	int i;
+	int xstate_size = FXSAVE_SIZE + XSAVE_HDR_SIZE;
+	int xstate_size_no_dynamic, i;
+
+	xstate_size_no_dynamic = xstate_size;
 
 	for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
+		bool user_dynamic;
+
 		if (!xfeature_enabled(i))
 			continue;
 
+		user_dynamic = (xfeatures_mask_user_dynamic & BIT_ULL(i)) ? true : false;
+
 		check_xstate_against_struct(i);
 		/*
 		 * Supervisor state components can be managed only by
@@ -617,27 +629,39 @@ static void do_extra_xstate_size_checks(void)
 			XSTATE_WARN_ON(xfeature_is_supervisor(i));
 
 		/* Align from the end of the previous feature */
-		if (xfeature_is_aligned(i))
-			paranoid_xstate_size = ALIGN(paranoid_xstate_size, 64);
+		if (xfeature_is_aligned(i)) {
+			xstate_size = ALIGN(xstate_size, 64);
+			if (!user_dynamic)
+				xstate_size_no_dynamic = ALIGN(xstate_size_no_dynamic, 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.
 		 */
-		if (!cpu_feature_enabled(X86_FEATURE_XSAVES))
-			paranoid_xstate_size = xfeature_uncompacted_offset(i);
+		if (!cpu_feature_enabled(X86_FEATURE_XSAVES)) {
+			xstate_size = xfeature_uncompacted_offset(i);
+			if (!user_dynamic)
+				xstate_size_no_dynamic = xfeature_uncompacted_offset(i);
+		}
 		/*
 		 * The compacted-format offset always depends on where
 		 * the previous state ended.
 		 */
-		paranoid_xstate_size += xfeature_size(i);
+		xstate_size += xfeature_size(i);
+		if (!user_dynamic)
+			xstate_size_no_dynamic += xfeature_size(i);
 	}
+
 	/*
 	 * The size accounts for all the possible states reserved in the
 	 * per-task buffer.  Check against the maximum size.
 	 */
-	XSTATE_WARN_ON(paranoid_xstate_size != get_xstate_config(XSTATE_MAX_SIZE));
+	XSTATE_WARN_ON(xstate_size != get_xstate_config(XSTATE_MAX_SIZE));
+
+	/* Record the one without dynamic states as the minimum. */
+	set_xstate_config(XSTATE_MIN_SIZE, xstate_size_no_dynamic);
 }
 
 
@@ -738,14 +762,11 @@ static int __init init_xstate_size(void)
 	 */
 	set_xstate_config(XSTATE_MAX_SIZE, possible_xstate_size);
 
-	/* Perform an extra check for the maximum size. */
-	do_extra_xstate_size_checks();
-
 	/*
-	 * Set the minimum to be the same as the maximum. The dynamic
-	 * user states are not supported yet.
+	 * Calculate and double-check the maximum size. Calculate and record
+	 * the minimum size.
 	 */
-	set_xstate_config(XSTATE_MIN_SIZE, possible_xstate_size);
+	calculate_xstate_sizes();
 
 	/* Ensure the minimum size fits in the statically-allocated buffer: */
 	if (!is_supported_xstate_size(get_xstate_config(XSTATE_MIN_SIZE)))
-- 
2.17.1


  reply	other threads:[~2021-07-02 15:23 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-30  6:02 [PATCH v6 00/26] x86: Support Intel Advanced Matrix Extensions Chang S. Bae
2021-06-30  6:02 ` [PATCH v6 01/26] x86/fpu/xstate: Modify the initialization helper to handle both static and dynamic buffers Chang S. Bae
2021-06-30  6:02 ` [PATCH v6 02/26] x86/fpu/xstate: Modify state copy helpers " Chang S. Bae
2021-06-30  6:02 ` [PATCH v6 03/26] x86/fpu/xstate: Modify address finders " Chang S. Bae
2021-06-30  6:02 ` [PATCH v6 04/26] x86/fpu/xstate: Add a new variable to indicate dynamic user states Chang S. Bae
2021-06-30  6:02 ` [PATCH v6 05/26] x86/fpu/xstate: Add new variables to indicate dynamic XSTATE buffer size Chang S. Bae
2021-06-30  6:02 ` [PATCH v6 06/26] x86/fpu/xstate: Calculate and remember dynamic XSTATE buffer sizes Chang S. Bae
2021-07-02 15:19   ` Bae, Chang Seok
2021-07-02 15:17     ` Chang S. Bae [this message]
2021-07-02 17:46       ` [PATCH v6-fix " Dave Hansen
2021-06-30  6:02 ` [PATCH v6 07/26] x86/fpu/xstate: Convert the struct fpu 'state' field to a pointer Chang S. Bae
2021-06-30  6:02 ` [PATCH v6 08/26] x86/fpu/xstate: Introduce helpers to manage the XSTATE buffer dynamically Chang S. Bae
2021-06-30  6:02 ` [PATCH v6 09/26] x86/fpu/xstate: Update the XSTATE save function to support dynamic states Chang S. Bae
2021-06-30  6:02 ` [PATCH v6 10/26] x86/fpu/xstate: Update the XSTATE buffer address finder " Chang S. Bae
2021-06-30  6:02 ` [PATCH v6 11/26] x86/fpu/xstate: Update the XSTATE context copy function " Chang S. Bae
2021-06-30  6:02 ` [PATCH v6 12/26] x86/fpu/xstate: Use feature disable (XFD) to protect dynamic user state Chang S. Bae
2021-06-30  6:02 ` [PATCH v6 13/26] x86/fpu/xstate: Support ptracer-induced XSTATE buffer expansion Chang S. Bae
2021-06-30  6:02 ` [PATCH v6 14/26] x86/arch_prctl: Create ARCH_ENABLE_XSTATE Chang S. Bae
2021-06-30  6:02 ` [PATCH v6 15/26] x86/fpu/xstate: Support both legacy and expanded signal XSTATE size Chang S. Bae
2021-06-30  6:02 ` [PATCH v6 16/26] x86/fpu/xstate: Adjust the XSAVE feature table to address gaps in state component numbers Chang S. Bae
2021-06-30  6:02 ` [PATCH v6 17/26] x86/fpu/xstate: Disable XSTATE support if an inconsistent state is detected Chang S. Bae
2021-06-30  6:02 ` [PATCH v6 18/26] x86/cpufeatures/amx: Enumerate Advanced Matrix Extension (AMX) feature bits Chang S. Bae
2021-06-30  6:02 ` [PATCH v6 19/26] x86/fpu/amx: Define AMX state components and have it used for boot-time checks Chang S. Bae
2021-06-30  6:02 ` [PATCH v6 20/26] x86/fpu/amx: Initialize child's AMX state Chang S. Bae
2021-06-30  6:02 ` [PATCH v6 21/26] x86/fpu/amx: Enable the AMX feature in 64-bit mode Chang S. Bae
2021-06-30  6:02 ` [PATCH v6 22/26] x86/fpu/xstate: Skip writing zeros to signal frame for dynamic user states if in INIT-state Chang S. Bae
2021-06-30  6:02 ` [PATCH v6 23/26] selftest/x86/amx: Test cases for the AMX state management Chang S. Bae
2021-06-30  6:02 ` [PATCH v6 24/26] x86/insn/amx: Add TILERELEASE instruction to the opcode map Chang S. Bae
2021-06-30  6:02 ` [PATCH v6 25/26] intel_idle/amx: Clear the AMX state before entering idle Chang S. Bae
2021-06-30 13:11   ` Rafael J. Wysocki
2021-06-30  6:02 ` [PATCH v6 26/26] x86/fpu/xstate: Add a sanity check for XFD state when saving XSTATE Chang S. Bae

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