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From:   Mike Hommey <mh@glandium.org>
To:     Borislav Petkov <bp@alien8.de>
Cc:     x86@kernel.org, linux-kernel@vger.kernel.org,
        Mike Hommey <mh@glandium.org>
Subject: [PATCH v3] x86/boot: Handle fpu-related and clearcpuid command line arguments earlier
Date:   Tue, 22 Sep 2020 06:56:38 +0900
Message-Id: <20200921215638.37980-1-mh@glandium.org>
In-Reply-To: <20200921131005.GF5901@zn.tnic>
References: <20200921131005.GF5901@zn.tnic>
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FPU initialization handles them currently. However, in the case of
clearcpuid, some other early initialization code may check for features
before the FPU initialization code is called. Handling the argument
earlier allows the command line to influence those early
initializations.

Signed-off-by: Mike Hommey <mh@glandium.org>
---
 arch/x86/kernel/cpu/common.c | 55 ++++++++++++++++++++++++++++++++++++
 arch/x86/kernel/fpu/init.c   | 55 ------------------------------------
 2 files changed, 55 insertions(+), 55 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 8d4715e84268..6220fae87263 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -23,6 +23,7 @@
 #include <linux/syscore_ops.h>
 #include <linux/pgtable.h>
 
+#include <asm/cmdline.h>
 #include <asm/stackprotector.h>
 #include <asm/perf_event.h>
 #include <asm/mmu_context.h>
@@ -1220,6 +1221,59 @@ static void detect_nopl(void)
 #endif
 }
 
+/*
+ * We parse cpu parameters early because fpu__init_system() is executed
+ * before parse_early_param().
+ */
+static void __init cpu_parse_early_param(void)
+{
+	char arg[128];
+	char *argptr = arg;
+	int arglen, res, bit;
+
+#ifdef CONFIG_X86_32
+	if (cmdline_find_option_bool(boot_command_line, "no387"))
+#ifdef CONFIG_MATH_EMULATION
+		setup_clear_cpu_cap(X86_FEATURE_FPU);
+#else
+		pr_err("Option 'no387' required CONFIG_MATH_EMULATION enabled.\n");
+#endif
+
+	if (cmdline_find_option_bool(boot_command_line, "nofxsr"))
+		setup_clear_cpu_cap(X86_FEATURE_FXSR);
+#endif
+
+	if (cmdline_find_option_bool(boot_command_line, "noxsave"))
+		setup_clear_cpu_cap(X86_FEATURE_XSAVE);
+
+	if (cmdline_find_option_bool(boot_command_line, "noxsaveopt"))
+		setup_clear_cpu_cap(X86_FEATURE_XSAVEOPT);
+
+	if (cmdline_find_option_bool(boot_command_line, "noxsaves"))
+		setup_clear_cpu_cap(X86_FEATURE_XSAVES);
+
+	arglen = cmdline_find_option(boot_command_line, "clearcpuid", arg, sizeof(arg));
+	if (arglen <= 0)
+		return;
+
+	pr_info("Clearing CPUID bits:");
+	do {
+		res = get_option(&argptr, &bit);
+		if (res == 0 || res == 3)
+			break;
+
+		/* If the argument was too long, the last bit may be cut off */
+		if (res == 1 && arglen >= sizeof(arg))
+			break;
+
+		if (bit >= 0 && bit < NCAPINTS * 32) {
+			pr_cont(" " X86_CAP_FMT, x86_cap_flag(bit));
+			setup_clear_cpu_cap(bit);
+		}
+	} while (res == 2);
+	pr_cont("\n");
+}
+
 /*
  * Do minimum CPU detection early.
  * Fields really needed: vendor, cpuid_level, family, model, mask,
@@ -1255,6 +1309,7 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
 		get_cpu_cap(c);
 		get_cpu_address_sizes(c);
 		setup_force_cpu_cap(X86_FEATURE_CPUID);
+		cpu_parse_early_param();
 
 		if (this_cpu->c_early_init)
 			this_cpu->c_early_init(c);
diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index f8ff895aaf7e..701f196d7c68 100644
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -5,7 +5,6 @@
 #include <asm/fpu/internal.h>
 #include <asm/tlbflush.h>
 #include <asm/setup.h>
-#include <asm/cmdline.h>
 
 #include <linux/sched.h>
 #include <linux/sched/task.h>
@@ -237,66 +236,12 @@ static void __init fpu__init_system_ctx_switch(void)
 	on_boot_cpu = 0;
 }
 
-/*
- * We parse fpu parameters early because fpu__init_system() is executed
- * before parse_early_param().
- */
-static void __init fpu__init_parse_early_param(void)
-{
-	char arg[128];
-	char *argptr = arg;
-	int arglen, res, bit;
-
-#ifdef CONFIG_X86_32
-	if (cmdline_find_option_bool(boot_command_line, "no387"))
-#ifdef CONFIG_MATH_EMULATION
-		setup_clear_cpu_cap(X86_FEATURE_FPU);
-#else
-		pr_err("Option 'no387' required CONFIG_MATH_EMULATION enabled.\n");
-#endif
-
-	if (cmdline_find_option_bool(boot_command_line, "nofxsr"))
-		setup_clear_cpu_cap(X86_FEATURE_FXSR);
-#endif
-
-	if (cmdline_find_option_bool(boot_command_line, "noxsave"))
-		setup_clear_cpu_cap(X86_FEATURE_XSAVE);
-
-	if (cmdline_find_option_bool(boot_command_line, "noxsaveopt"))
-		setup_clear_cpu_cap(X86_FEATURE_XSAVEOPT);
-
-	if (cmdline_find_option_bool(boot_command_line, "noxsaves"))
-		setup_clear_cpu_cap(X86_FEATURE_XSAVES);
-
-	arglen = cmdline_find_option(boot_command_line, "clearcpuid", arg, sizeof(arg));
-	if (arglen <= 0)
-		return;
-
-	pr_info("Clearing CPUID bits:");
-	do {
-		res = get_option(&argptr, &bit);
-		if (res == 0 || res == 3)
-			break;
-
-		/* If the argument was too long, the last bit may be cut off */
-		if (res == 1 && arglen >= sizeof(arg))
-			break;
-
-		if (bit >= 0 && bit < NCAPINTS * 32) {
-			pr_cont(" " X86_CAP_FMT, x86_cap_flag(bit));
-			setup_clear_cpu_cap(bit);
-		}
-	} while (res == 2);
-	pr_cont("\n");
-}
-
 /*
  * Called on the boot CPU once per system bootup, to set up the initial
  * FPU state that is later cloned into all processes:
  */
 void __init fpu__init_system(struct cpuinfo_x86 *c)
 {
-	fpu__init_parse_early_param();
 	fpu__init_system_early_generic(c);
 
 	/*
-- 
2.28.0