[tip:x86/mm] x86/gdt: Fix setup_fixmap_gdt() to use the correct PA

[tip-bot for Andy Lutomirski <tipbot@zytor.com>]

Commit-ID:  aa4ea675528f3fa11e9663e5a32f55a81c34dcac
Gitweb:     http://git.kernel.org/tip/aa4ea675528f3fa11e9663e5a32f55a81c34dcac
Author:     Andy Lutomirski <luto@kernel.org>
AuthorDate: Wed, 22 Mar 2017 14:32:30 -0700
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 23 Mar 2017 08:25:07 +0100

x86/gdt: Fix setup_fixmap_gdt() to use the correct PA

__pa() cannot be used on percpu pointers because they may be
virtually mapped.  Use per_cpu_ptr_to_phys() instead.

This fixes a boot crash on a some 32-bit configurations.  I assume
this is related to which allocation strategy is chosen by the percpu
core.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
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: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Garnier <thgarnie@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 69218e47994d x86: ("Remap GDT tables in the fixmap section")
Link: http://lkml.kernel.org/r/22e0069c29fba31998f193201e359eebfdac4960.1490218061.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/include/asm/desc.h  | 6 ++++++
 arch/x86/kernel/cpu/common.c | 4 ++--
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/desc.h b/arch/x86/include/asm/desc.h
index ec05f9c..bde1169 100644
--- a/arch/x86/include/asm/desc.h
+++ b/arch/x86/include/asm/desc.h
@@ -98,6 +98,12 @@ static inline unsigned long get_current_gdt_ro_vaddr(void)
 	return (unsigned long)get_current_gdt_ro();
 }
 
+/* Provide the physical address of the GDT page. */
+static inline phys_addr_t get_cpu_gdt_paddr(unsigned int cpu)
+{
+	return per_cpu_ptr_to_phys(get_cpu_gdt_rw(cpu));
+}
+
 #ifdef CONFIG_X86_64
 
 static inline void pack_gate(gate_desc *gate, unsigned type, unsigned long func,
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index f8e22db..f6e20e2 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -461,8 +461,8 @@ pgprot_t pg_fixmap_gdt_flags = PAGE_KERNEL;
 /* Setup the fixmap mapping only once per-processor */
 static inline void setup_fixmap_gdt(int cpu)
 {
-	__set_fixmap(get_cpu_gdt_ro_index(cpu),
-		     __pa(get_cpu_gdt_rw(cpu)), pg_fixmap_gdt_flags);
+	__set_fixmap(get_cpu_gdt_ro_index(cpu), get_cpu_gdt_paddr(cpu),
+		     pg_fixmap_gdt_flags);
 }
 
 /* Load the original GDT from the per-cpu structure */