linux-kernel - [RFC 09/13] x86/mm: Disable interrupts when flushing the TLB using CR3

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Date:	Fri,  8 Jan 2016 15:15:27 -0800
From:	Andy Lutomirski <luto@...nel.org>
To:	x86@...nel.org, linux-kernel@...r.kernel.org
Cc:	Borislav Petkov <bp@...en8.de>, Brian Gerst <brgerst@...il.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Andy Lutomirski <luto@...nel.org>
Subject: [RFC 09/13] x86/mm: Disable interrupts when flushing the TLB using CR3

Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
 arch/x86/include/asm/tlbflush.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
index 3d905f12cda9..32e3d8769a22 100644
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -135,7 +135,17 @@ static inline void cr4_set_bits_and_update_boot(unsigned long mask)
 
 static inline void __native_flush_tlb(void)
 {
+	unsigned long flags;
+
+	/*
+	 * We mustn't be preempted or handle an IPI while reading and
+	 * writing CR3.  Preemption could switch mms and switch back, and
+	 * an IPI could call leave_mm.  Either of those could cause our
+	 * PCID to change asynchronously.
+	 */
+	raw_local_irq_save(flags);
 	native_write_cr3(native_read_cr3());
+	raw_local_irq_restore(flags);
 }
 
 static inline void __native_flush_tlb_global_irq_disabled(void)
-- 
2.5.0