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x86/boot: Synchronize trampoline_cr4_features and mmu_cr4_features directly

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The initialization process for trampoline_cr4_features and
mmu_cr4_features was confusing.  The intent is for mmu_cr4_features
and *trampoline_cr4_features to stay in sync, but
trampoline_cr4_features is NULL until setup_real_mode() runs.  The
old code synchronized *trampoline_cr4_features *twice*, once in
setup_real_mode() and once in setup_arch().  It also initialized
mmu_cr4_features in setup_real_mode(), which causes the actual value
of mmu_cr4_features to potentially depend on when setup_real_mode()
is called.

With this patch, mmu_cr4_features is initialized directly in
setup_arch(), and *trampoline_cr4_features is synchronized to
mmu_cr4_features when the trampoline is set up.

After this patch, it should be safe to defer setup_real_mode().

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mario Limonciello <mario_limonciello@dell.com>
Cc: Matt Fleming <mfleming@suse.de>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/d48a263f9912389b957dd495a7127b009259ffe0.1470821230.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2016-08-10 02:29:14 -07:00 committed by Ingo Molnar
parent 007b756053
commit 18bc7bd523
2 changed files with 12 additions and 8 deletions
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17
arch/x86/kernel/setup.c
View File

@ -1131,6 +1131,16 @@ void __init setup_arch(char **cmdline_p)
early_trap_pf_init();
/*
* Update mmu_cr4_features (and, indirectly, trampoline_cr4_features)
* with the current CR4 value. This may not be necessary, but
* auditing all the early-boot CR4 manipulation would be needed to
* rule it out.
*/
if (boot_cpu_data.cpuid_level >= 0)
/* A CPU has %cr4 if and only if it has CPUID. */
mmu_cr4_features = __read_cr4();
setup_real_mode();
memblock_set_current_limit(get_max_mapped());
@ -1180,13 +1190,6 @@ void __init setup_arch(char **cmdline_p)
kasan_init();
if (boot_cpu_data.cpuid_level >= 0) {
/* A CPU has %cr4 if and only if it has CPUID */
mmu_cr4_features = __read_cr4();
if (trampoline_cr4_features)
*trampoline_cr4_features = mmu_cr4_features;
}
#ifdef CONFIG_X86_32
/* sync back kernel address range */
clone_pgd_range(initial_page_table + KERNEL_PGD_BOUNDARY,

3
arch/x86/realmode/init.c
View File

@ -4,6 +4,7 @@
#include <asm/cacheflush.h>
#include <asm/pgtable.h>
#include <asm/realmode.h>
#include <asm/tlbflush.h>
struct real_mode_header *real_mode_header;
u32 *trampoline_cr4_features;
@ -84,7 +85,7 @@ void __init setup_real_mode(void)
trampoline_header->start = (u64) secondary_startup_64;
trampoline_cr4_features = &trampoline_header->cr4;
*trampoline_cr4_features = __read_cr4();
*trampoline_cr4_features = mmu_cr4_features;
trampoline_pgd = (u64 *) __va(real_mode_header->trampoline_pgd);
trampoline_pgd[0] = trampoline_pgd_entry.pgd;