When using VHE, the host needs to clear HCR_EL2.TGE bit in order
to interract with guest TLBs, switching from EL2&0 translation regime
to EL1&0.

However, some non-maskable asynchronous event could happen while TGE is
cleared like SDEI. Because of this address translation operations
relying on EL2&0 translation regime could fail (tlb invalidation,
userspace access, ...).

Fix this by properly setting HCR_EL2.TGE when entering NMI context and
clear it if necessary when returning to the interrupted context.

Signed-off-by: Julien Thierry <redacted>
Suggested-by: Marc Zyngier <redacted>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <redacted>
Cc: Marc Zyngier <redacted>
Cc: James Morse <james.morse@arm.com>
Cc: linux-arch@vger.kernel.org
Cc: stable@vger.kernel.org
---
 arch/arm64/include/asm/hardirq.h | 28 ++++++++++++++++++++++++++++
 arch/arm64/kernel/irq.c          |  3 +++
 include/asm-generic/hardirq.h    |  3 +++
 include/linux/hardirq.h          |  2 ++
 4 files changed, 36 insertions(+)

diff --git a/include/asm-generic/hardirq.h b/include/asm-generic/hardirq.h
index d14214d..c33b53f20 100644
--- a/include/asm-generic/hardirq.h
+++ b/include/asm-generic/hardirq.h

@@ -12,6 +12,9 @@
 #include <linux/irq_cpustat.h>	/* Standard mappings for irq_cpustat_t above */
 #include <linux/irq.h>
 
+#define arch_nmi_enter()	do { } while (0)
+#define arch_nmi_exit()		do { } while (0)
+

 #ifndef ack_bad_irq
 static inline void ack_bad_irq(unsigned int irq)
 {

diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index 0fbbcdf..776a60f 100644
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h

@@ -62,6 +62,7 @@ static inline void rcu_nmi_exit(void)
 
 #define nmi_enter()						\
 	do {							\
+		arch_nmi_enter();				\
 		printk_nmi_enter();				\
 		lockdep_off();					\
 		ftrace_nmi_enter();				\

@@ -80,6 +81,7 @@ static inline void rcu_nmi_exit(void)
 		ftrace_nmi_exit();				\
 		lockdep_on();					\
 		printk_nmi_exit();				\
+		arch_nmi_exit();				\
 	} while (0)
 
 #endif /* LINUX_HARDIRQ_H */