[v4][PATCH 3/7] book3e/kgdb: update thread's dbcr0

[Tiejun Chen <tiejun.chen@windriver.com>]

gdb always need to generate a single step properly to invoke
a kgdb state. But with lazy interrupt, book3e can't always
trigger a debug exception with a single step since the current
is blocked for handling those pending exception, then we miss
that expected dbcr configuration at last to generate a debug
exception.

So here we also update thread's dbcr0 to make sure the current
can go back with that missed dbcr0 configuration.

Signed-off-by: Tiejun Chen <tiejun.chen@windriver.com>
---
 arch/powerpc/kernel/kgdb.c |   13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/kgdb.c b/arch/powerpc/kernel/kgdb.c
index 5ca82cd..1a57307 100644
--- a/arch/powerpc/kernel/kgdb.c
+++ b/arch/powerpc/kernel/kgdb.c
@@ -410,7 +410,7 @@ int kgdb_arch_handle_exception(int vector, int signo, int err_code,
 			       struct pt_regs *linux_regs)
 {
 	char *ptr = &remcom_in_buffer[1];
-	unsigned long addr;
+	unsigned long addr, dbcr0;
 
 	switch (remcom_in_buffer[0]) {
 		/*
@@ -427,8 +427,15 @@ int kgdb_arch_handle_exception(int vector, int signo, int err_code,
 		/* set the trace bit if we're stepping */
 		if (remcom_in_buffer[0] == 's') {
 #ifdef CONFIG_PPC_ADV_DEBUG_REGS
-			mtspr(SPRN_DBCR0,
-			      mfspr(SPRN_DBCR0) | DBCR0_IC | DBCR0_IDM);
+			dbcr0 = mfspr(SPRN_DBCR0) | DBCR0_IC | DBCR0_IDM;
+			mtspr(SPRN_DBCR0, dbcr0);
+#ifdef CONFIG_PPC_BOOK3E_64
+			/* With lazy interrut we have to update thread dbcr0 here
+			 * to make sure we can set debug properly at last to invoke
+			 * kgdb again to work well.
+			 */
+			current->thread.dbcr0 = dbcr0;
+#endif
 			linux_regs->msr |= MSR_DE;
 #else
 			linux_regs->msr |= MSR_SE;
-- 
1.7.9.5