linux-kernel - [tip: x86/urgent] x86/fpu/xstate: Consolidate size calculations

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Message-ID: <164871725283.389.1793591339458620875.tip-bot2@tip-bot2>
Date:   Thu, 31 Mar 2022 09:00:52 -0000
From:   "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     kernel test robot <oliver.sang@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...e.de>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: x86/urgent] x86/fpu/xstate: Consolidate size calculations

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

Commit-ID:     d6d6d50f1e801a790a242c80eeda261e36c43b7b
Gitweb:        https://git.kernel.org/tip/d6d6d50f1e801a790a242c80eeda261e36c43b7b
Author:        Thomas Gleixner <tglx@...utronix.de>
AuthorDate:    Mon, 28 Mar 2022 20:43:21 +02:00
Committer:     Borislav Petkov <bp@...e.de>
CommitterDate: Wed, 30 Mar 2022 12:04:09 +02:00

x86/fpu/xstate: Consolidate size calculations

Use the offset calculation to do the size calculation which avoids yet
another series of CPUID instructions for each invocation.

  [ Fix the FP/SSE only case which missed to take the xstate
    header into account, as
    Reported-by: kernel test robot <oliver.sang@...el.com> ]

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Borislav Petkov <bp@...e.de>
Link: https://lore.kernel.org/r/87o81pgbp2.ffs@tglx
---
 arch/x86/kernel/fpu/xstate.c | 49 +++++------------------------------
 1 file changed, 8 insertions(+), 41 deletions(-)

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 5ac934b..39e1c86 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -385,25 +385,6 @@ static void __init setup_init_fpu_buf(void)
 	fxsave(&init_fpstate.regs.fxsave);
 }
 
-static int xfeature_uncompacted_offset(int xfeature_nr)
-{
-	u32 eax, ebx, ecx, edx;
-
-	/*
-	 * Only XSAVES supports supervisor states and it uses compacted
-	 * format. Checking a supervisor state's uncompacted offset is
-	 * an error.
-	 */
-	if (XFEATURE_MASK_SUPERVISOR_ALL & BIT_ULL(xfeature_nr)) {
-		WARN_ONCE(1, "No fixed offset for xstate %d\n", xfeature_nr);
-		return -1;
-	}
-
-	CHECK_XFEATURE(xfeature_nr);
-	cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
-	return ebx;
-}
-
 int xfeature_size(int xfeature_nr)
 {
 	u32 eax, ebx, ecx, edx;
@@ -581,29 +562,15 @@ static bool __init check_xstate_against_struct(int nr)
 
 static unsigned int xstate_calculate_size(u64 xfeatures, bool compacted)
 {
-	unsigned int size = FXSAVE_SIZE + XSAVE_HDR_SIZE;
-	int i;
+	unsigned int topmost = fls64(xfeatures) -  1;
+	unsigned int offset = xstate_offsets[topmost];
 
-	for_each_extended_xfeature(i, xfeatures) {
-		/* Align from the end of the previous feature */
-		if (xfeature_is_aligned64(i))
-			size = ALIGN(size, 64);
-		/*
-		 * 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 (!compacted)
-			size = xfeature_uncompacted_offset(i);
-		/*
-		 * Add the feature size even for non-compacted format
-		 * to make the end result correct
-		 */
-		size += xfeature_size(i);
-	}
-	return size;
+	if (topmost <= XFEATURE_SSE)
+		return sizeof(struct xregs_state);
+
+	if (compacted)
+		offset = xfeature_get_offset(xfeatures, topmost);
+	return offset + xstate_sizes[topmost];
 }
 
 /*