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x86/cpu: Drop wp_works_ok member of struct cpuinfo_x86

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Remove the wp_works_ok member of struct cpuinfo_x86. It's an
optimization back from Linux v0.99 times where we had no fixup support
yet and did the CR0.WP test via special code in the page fault handler.
The < 0 test was an optimization to not do the special casing for each
NULL ptr access violation but just for the first one doing the WP test.
Today it serves no real purpose as the test no longer needs special code
in the page fault handler and the only call side -- mem_init() -- calls
it just once, anyway. However, Xen pre-initializes it to 1, to skip the
test.

Doing the test again for Xen should be no issue at all, as even the
commit introducing skipping the test (commit d560bc6157 ("x86, xen:
Suppress WP test on Xen")) mentioned it being ban aid only. And, in
fact, testing the patch on Xen showed nothing breaks.

The pre-fixup times are long gone and with the removal of the fallback
handling code in commit a5c2a893db ("x86, 386 removal: Remove
CONFIG_X86_WP_WORKS_OK") the kernel requires a working CR0.WP anyway.
So just get rid of the "optimization" and do the test unconditionally.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Jesper Nilsson <jesper.nilsson@axis.com>
Cc: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Arnd Hannemann <hannemann@nets.rwth-aachen.de>
Cc: Mikael Starvik <starvik@axis.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: "David S. Miller" <davem@davemloft.net>
Link: http://lkml.kernel.org/r/1486933932-585-3-git-send-email-minipli@googlemail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Mathias Krause 2017-02-12 22:12:08 +01:00 committed by Thomas Gleixner
parent 0440211684
commit 6415813bae
5 changed files with 12 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
arch/x86/include/asm/processor.h
View File

@ -89,9 +89,7 @@ struct cpuinfo_x86 {
__u8 x86_vendor; /* CPU vendor */
__u8 x86_model;
__u8 x86_mask;
#ifdef CONFIG_X86_32
char wp_works_ok; /* It doesn't on 386's */
#else
#ifdef CONFIG_X86_64
/* Number of 4K pages in DTLB/ITLB combined(in pages): */
int x86_tlbsize;
#endif

5
arch/x86/kernel/cpu/proc.c
View File

@ -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)

11
arch/x86/kernel/setup.c
View File

@ -173,14 +173,11 @@ 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,
};
/* cpu data as detected by the assembly code in head_32.S */
struct cpuinfo_x86 new_cpu_data;
/* common cpu data for all cpus */
struct cpuinfo_x86 boot_cpu_data __read_mostly = {
.wp_works_ok = -1,
};
struct cpuinfo_x86 boot_cpu_data __read_mostly;
EXPORT_SYMBOL(boot_cpu_data);
unsigned int def_to_bigsmp;

9
arch/x86/mm/init_32.c
View File

@ -716,15 +716,17 @@ void __init paging_init(void)
*/
static void __init test_wp_bit(void)
{
int wp_works_ok;
printk(KERN_INFO
"Checking if this processor honours the WP bit even in supervisor mode...");
/* 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();
wp_works_ok = do_test_wp_bit();
clear_fixmap(FIX_WP_TEST);
if (!boot_cpu_data.wp_works_ok) {
if (!wp_works_ok) {
printk(KERN_CONT "No.\n");
panic("Linux doesn't support CPUs with broken WP.");
} else {
@ -811,8 +813,7 @@ 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

1
arch/x86/xen/enlighten.c
View File

@ -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