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Subject[tip: x86/mm] x86/tlb: Uninline __get_current_cr3_fast()
The following commit has been merged into the x86/mm branch of tip:

Commit-ID: 8c5cc19e94703182647dfccc164e4437a04539c8
Gitweb: https://git.kernel.org/tip/8c5cc19e94703182647dfccc164e4437a04539c8
Author: Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Tue, 21 Apr 2020 11:20:28 +02:00
Committer: Borislav Petkov <bp@suse.de>
CommitterDate: Fri, 24 Apr 2020 15:55:50 +02:00

x86/tlb: Uninline __get_current_cr3_fast()

cpu_tlbstate is exported because various TLB-related functions need
access to it, but cpu_tlbstate is sensitive information which should
only be accessed by well-contained kernel functions and not be directly
exposed to modules.

In preparation for unexporting cpu_tlbstate move __get_current_cr3_fast()
into the x86 TLB management code.

No functional change.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200421092558.848064318@linutronix.de
---
arch/x86/include/asm/mmu_context.h | 19 +------------------
arch/x86/mm/tlb.c | 20 ++++++++++++++++++++
2 files changed, 21 insertions(+), 18 deletions(-)

diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index 4e55370..9608536 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -225,24 +225,7 @@ static inline bool arch_vma_access_permitted(struct vm_area_struct *vma,
return __pkru_allows_pkey(vma_pkey(vma), write);
}

-/*
- * This can be used from process context to figure out what the value of
- * CR3 is without needing to do a (slow) __read_cr3().
- *
- * It's intended to be used for code like KVM that sneakily changes CR3
- * and needs to restore it. It needs to be used very carefully.
- */
-static inline unsigned long __get_current_cr3_fast(void)
-{
- unsigned long cr3 = build_cr3(this_cpu_read(cpu_tlbstate.loaded_mm)->pgd,
- this_cpu_read(cpu_tlbstate.loaded_mm_asid));
-
- /* For now, be very restrictive about when this can be called. */
- VM_WARN_ON(in_nmi() || preemptible());
-
- VM_BUG_ON(cr3 != __read_cr3());
- return cr3;
-}
+unsigned long __get_current_cr3_fast(void);

typedef struct {
struct mm_struct *mm;
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 66f96f2..ea6f98a 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -844,6 +844,26 @@ void flush_tlb_kernel_range(unsigned long start, unsigned long end)
}

/*
+ * This can be used from process context to figure out what the value of
+ * CR3 is without needing to do a (slow) __read_cr3().
+ *
+ * It's intended to be used for code like KVM that sneakily changes CR3
+ * and needs to restore it. It needs to be used very carefully.
+ */
+unsigned long __get_current_cr3_fast(void)
+{
+ unsigned long cr3 = build_cr3(this_cpu_read(cpu_tlbstate.loaded_mm)->pgd,
+ this_cpu_read(cpu_tlbstate.loaded_mm_asid));
+
+ /* For now, be very restrictive about when this can be called. */
+ VM_WARN_ON(in_nmi() || preemptible());
+
+ VM_BUG_ON(cr3 != __read_cr3());
+ return cr3;
+}
+EXPORT_SYMBOL_GPL(__get_current_cr3_fast);
+
+/*
* arch_tlbbatch_flush() performs a full TLB flush regardless of the active mm.
* This means that the 'struct flush_tlb_info' that describes which mappings to
* flush is actually fixed. We therefore set a single fixed struct and use it in
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