[OE-core] [PATCH 2/6] qemu: Add patch to avoid qemuppc boot hangs

[Richard Purdie]

qemuppc boots are occasionally hanging on the autobuilder. This adds a
patch which fixes the issue in local testing. Its being discussed with
upstream qemu.

Signed-off-by: Richard Purdie <richard.purdie at linuxfoundation.org>
---
 meta/recipes-devtools/qemu/qemu/ppc_locking.patch | 105 ++++++++++++++++++++++
 meta/recipes-devtools/qemu/qemu_2.10.1.bb         |   1 +
 2 files changed, 106 insertions(+)
 create mode 100644 meta/recipes-devtools/qemu/qemu/ppc_locking.patch

diff --git a/meta/recipes-devtools/qemu/qemu/ppc_locking.patch b/meta/recipes-devtools/qemu/qemu/ppc_locking.patch
new file mode 100644
index 0000000..6f72243
--- /dev/null
+++ b/meta/recipes-devtools/qemu/qemu/ppc_locking.patch
@@ -0,0 +1,105 @@
+I've tracked down what I think is a problem causing qemu-system-ppc
+to hang whilst booting images.
+
+I believe the decrementer timer stops receiving interrupts so
+tasks in our images hang indefinitely as the timer stopped. 
+
+It can be summed up with this line of debug:
+
+ppc_set_irq: 0x55b4e0d562f0 n_IRQ 8 level 1 => pending 00000100req 00000004
+
+It should normally read:
+
+ppc_set_irq: 0x55b4e0d562f0 n_IRQ 8 level 1 => pending 00000100req 00000002
+
+The question is why CPU_INTERRUPT_EXITTB ends up being set when the
+lines above this log message clearly sets CPU_INTERRUPT_HARD (via 
+cpu_interrupt() ).
+
+I note in cpu.h:
+
+    /* updates protected by BQL */
+    uint32_t interrupt_request;
+
+(for struct CPUState)
+
+The ppc code does "cs->interrupt_request |= CPU_INTERRUPT_EXITTB" in 5
+places, 3 in excp_helper.c and 2 in helper_regs.h. In all cases,  
+g_assert(qemu_mutex_iothread_locked()); fails. If I do something like:
+
+if (!qemu_mutex_iothread_locked()) {
+    qemu_mutex_lock_iothread();
+    cpu_interrupt(cs, CPU_INTERRUPT_EXITTB);
+    qemu_mutex_unlock_iothread();
+} else {
+    cpu_interrupt(cs, CPU_INTERRUPT_EXITTB);
+}
+
+in these call sites then I can no longer lock qemu up with my test
+case.
+
+I suspect the _HARD setting gets overwritten which stops the 
+decrementer interrupts being delivered.
+
+Upstream-Status: Submitted [Issue discussed on qemu mailing list 2017/11/20]
+RP 2017/11/20
+
+Index: qemu-2.10.1/target/ppc/excp_helper.c
+===================================================================
+--- qemu-2.10.1.orig/target/ppc/excp_helper.c
++++ qemu-2.10.1/target/ppc/excp_helper.c
+@@ -207,7 +207,9 @@ static inline void powerpc_excp(PowerPCC
+                         "Entering checkstop state\n");
+             }
+             cs->halted = 1;
+-            cs->interrupt_request |= CPU_INTERRUPT_EXITTB;
++            qemu_mutex_lock_iothread();
++            cpu_interrupt(cs, CPU_INTERRUPT_EXITTB);
++            qemu_mutex_unlock_iothread();
+         }
+         if (env->msr_mask & MSR_HVB) {
+             /* ISA specifies HV, but can be delivered to guest with HV clear
+@@ -940,7 +942,9 @@ void helper_store_msr(CPUPPCState *env,
+ 
+     if (excp != 0) {
+         CPUState *cs = CPU(ppc_env_get_cpu(env));
+-        cs->interrupt_request |= CPU_INTERRUPT_EXITTB;
++        qemu_mutex_lock_iothread();
++        cpu_interrupt(cs, CPU_INTERRUPT_EXITTB);
++        qemu_mutex_unlock_iothread();
+         raise_exception(env, excp);
+     }
+ }
+@@ -995,7 +999,9 @@ static inline void do_rfi(CPUPPCState *e
+     /* No need to raise an exception here,
+      * as rfi is always the last insn of a TB
+      */
+-    cs->interrupt_request |= CPU_INTERRUPT_EXITTB;
++    qemu_mutex_lock_iothread();
++    cpu_interrupt(cs, CPU_INTERRUPT_EXITTB);
++    qemu_mutex_unlock_iothread();
+ 
+     /* Reset the reservation */
+     env->reserve_addr = -1;
+Index: qemu-2.10.1/target/ppc/helper_regs.h
+===================================================================
+--- qemu-2.10.1.orig/target/ppc/helper_regs.h
++++ qemu-2.10.1/target/ppc/helper_regs.h
+@@ -114,11 +114,15 @@ static inline int hreg_store_msr(CPUPPCS
+     }
+     if (((value >> MSR_IR) & 1) != msr_ir ||
+         ((value >> MSR_DR) & 1) != msr_dr) {
+-        cs->interrupt_request |= CPU_INTERRUPT_EXITTB;
++        qemu_mutex_lock_iothread();
++        cpu_interrupt(cs, CPU_INTERRUPT_EXITTB);
++        qemu_mutex_unlock_iothread();
+     }
+     if ((env->mmu_model & POWERPC_MMU_BOOKE) &&
+         ((value >> MSR_GS) & 1) != msr_gs) {
+-        cs->interrupt_request |= CPU_INTERRUPT_EXITTB;
++        qemu_mutex_lock_iothread();
++        cpu_interrupt(cs, CPU_INTERRUPT_EXITTB);
++        qemu_mutex_unlock_iothread();
+     }
+     if (unlikely((env->flags & POWERPC_FLAG_TGPR) &&
+                  ((value ^ env->msr) & (1 << MSR_TGPR)))) {
diff --git a/meta/recipes-devtools/qemu/qemu_2.10.1.bb b/meta/recipes-devtools/qemu/qemu_2.10.1.bb
index 6e9b68b..8e3ca3c 100644
--- a/meta/recipes-devtools/qemu/qemu_2.10.1.bb
+++ b/meta/recipes-devtools/qemu/qemu_2.10.1.bb
@@ -24,6 +24,7 @@ SRC_URI = "http://wiki.qemu-project.org/download/${BP}.tar.bz2 \
            file://0003-Introduce-condition-in-TPM-backend-for-notification.patch \
            file://0004-Add-support-for-VM-suspend-resume-for-TPM-TIS-v2.9.patch \
            file://apic-fixup-fallthrough-to-PIC.patch \
+           file://ppc_locking.patch \
            "
 UPSTREAM_CHECK_REGEX = "qemu-(?P<pver>\d+\..*)\.tar"
 
-- 
2.7.4