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Subject[tip:x86/urgent] x86/mm/32: Load a sane CR3 before cpu_init() on secondary CPUs
Commit-ID:  4ba55e65f471d011d3ba2ac2022180ea0877d68e
Gitweb: http://git.kernel.org/tip/4ba55e65f471d011d3ba2ac2022180ea0877d68e
Author: Andy Lutomirski <luto@kernel.org>
AuthorDate: Sun, 17 Sep 2017 09:03:51 -0700
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Sun, 17 Sep 2017 18:59:09 +0200

x86/mm/32: Load a sane CR3 before cpu_init() on secondary CPUs

For unknown historical reasons (i.e. Borislav doesn't recall),
32-bit kernels invoke cpu_init() on secondary CPUs with
initial_page_table loaded into CR3. Then they set
current->active_mm to &init_mm and call enter_lazy_tlb() before
fixing CR3. This means that the x86 TLB code gets invoked while CR3
is inconsistent, and, with the improved PCID sanity checks I added,
we warn.

Fix it by loading swapper_pg_dir (i.e. init_mm.pgd) earlier.

Reported-by: Paul Menzel <pmenzel@molgen.mpg.de>
Reported-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 72c0098d92ce ("x86/mm: Reinitialize TLB state on hotplug and resume")
Link: http://lkml.kernel.org/r/30cdfea504682ba3b9012e77717800a91c22097f.1505663533.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/kernel/smpboot.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 0854ff1..ad59edd 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -232,12 +232,6 @@ static void notrace start_secondary(void *unused)
*/
if (boot_cpu_has(X86_FEATURE_PCID))
__write_cr4(__read_cr4() | X86_CR4_PCIDE);
- cpu_init();
- x86_cpuinit.early_percpu_clock_init();
- preempt_disable();
- smp_callin();
-
- enable_start_cpu0 = 0;

#ifdef CONFIG_X86_32
/* switch away from the initial page table */
@@ -245,6 +239,13 @@ static void notrace start_secondary(void *unused)
__flush_tlb_all();
#endif

+ cpu_init();
+ x86_cpuinit.early_percpu_clock_init();
+ preempt_disable();
+ smp_callin();
+
+ enable_start_cpu0 = 0;
+
/* otherwise gcc will move up smp_processor_id before the cpu_init */
barrier();
/*
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