[PATCH v2 1/2] x86/boot/32: Delete cpuinfo_x86::wp_works_ok

From: Andy Lutomirski
Date: Wed Mar 29 2017 - 12:49:02 EST


Linux refuses to boot if WP doesn't work okay, so tracking whether
it works serves no purpose. The only use I can see at all for wp_works_ok
is that it lets Xen bypass test_wp_bit(). If this is truly needed,
it could be more cleanly handled using X86_FEATURE_XENPV, but it
looks like Xen can handle test_wp_bit() correctly without special
cases at all.

Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
---
arch/x86/include/asm/processor.h | 2 --
arch/x86/kernel/cpu/proc.c | 5 ++---
arch/x86/kernel/setup.c | 2 --
arch/x86/mm/init_32.c | 13 +++++--------
arch/x86/xen/enlighten.c | 1 -
5 files changed, 7 insertions(+), 16 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 05319c60b3db..1ac08e96411c 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -90,8 +90,6 @@ struct cpuinfo_x86 {
__u8 x86_model;
__u8 x86_mask;
#ifdef CONFIG_X86_32
- char wp_works_ok; /* It doesn't on 386's */
-
/* Problems on some 486Dx4's and old 386's: */
char rfu;
char pad0;
diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c
index 18ca99f2798b..6df621ae62a7 100644
--- a/arch/x86/kernel/cpu/proc.c
+++ b/arch/x86/kernel/cpu/proc.c
@@ -31,14 +31,13 @@ static void show_cpuinfo_misc(struct seq_file *m, struct cpuinfo_x86 *c)
"fpu\t\t: %s\n"
"fpu_exception\t: %s\n"
"cpuid level\t: %d\n"
- "wp\t\t: %s\n",
+ "wp\t\t: yes\n",
static_cpu_has_bug(X86_BUG_FDIV) ? "yes" : "no",
static_cpu_has_bug(X86_BUG_F00F) ? "yes" : "no",
static_cpu_has_bug(X86_BUG_COMA) ? "yes" : "no",
static_cpu_has(X86_FEATURE_FPU) ? "yes" : "no",
static_cpu_has(X86_FEATURE_FPU) ? "yes" : "no",
- c->cpuid_level,
- c->wp_works_ok ? "yes" : "no");
+ c->cpuid_level);
}
#else
static void show_cpuinfo_misc(struct seq_file *m, struct cpuinfo_x86 *c)
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 56b1177155db..462b7c69443d 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -175,11 +175,9 @@ static struct resource bss_resource = {
#ifdef CONFIG_X86_32
/* cpu data as detected by the assembly code in head.S */
struct cpuinfo_x86 new_cpu_data = {
- .wp_works_ok = -1,
};
/* common cpu data for all cpus */
struct cpuinfo_x86 boot_cpu_data __read_mostly = {
- .wp_works_ok = -1,
};
EXPORT_SYMBOL(boot_cpu_data);

diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
index 5ed3c141bbd5..b30f20951e9e 100644
--- a/arch/x86/mm/init_32.c
+++ b/arch/x86/mm/init_32.c
@@ -731,15 +731,13 @@ static void __init test_wp_bit(void)

/* Any page-aligned address will do, the test is non-destructive */
__set_fixmap(FIX_WP_TEST, __pa(&swapper_pg_dir), PAGE_KERNEL_RO);
- boot_cpu_data.wp_works_ok = do_test_wp_bit();
- clear_fixmap(FIX_WP_TEST);
-
- if (!boot_cpu_data.wp_works_ok) {
+ if (!do_test_wp_bit()) {
printk(KERN_CONT "No.\n");
panic("Linux doesn't support CPUs with broken WP.");
- } else {
- printk(KERN_CONT "Ok.\n");
}
+ clear_fixmap(FIX_WP_TEST);
+
+ printk(KERN_CONT "Ok.\n");
}

void __init mem_init(void)
@@ -821,8 +819,7 @@ void __init mem_init(void)
BUG_ON(VMALLOC_START >= VMALLOC_END);
BUG_ON((unsigned long)high_memory > VMALLOC_START);

- if (boot_cpu_data.wp_works_ok < 0)
- test_wp_bit();
+ test_wp_bit();
}

#ifdef CONFIG_MEMORY_HOTPLUG
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 4951fcf95143..6efa0cc425a2 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1595,7 +1595,6 @@ asmlinkage __visible void __init xen_start_kernel(void)
/* set up basic CPUID stuff */
cpu_detect(&new_cpu_data);
set_cpu_cap(&new_cpu_data, X86_FEATURE_FPU);
- new_cpu_data.wp_works_ok = 1;
new_cpu_data.x86_capability[CPUID_1_EDX] = cpuid_edx(1);
#endif

--
2.9.3