If we take an interrupt such as a trap caused by a BUG_ON before the
MMU has been setup, the interrupt handlers try to enable virutal mode
and cause a recursive crash, making the original problem very hard
to debug.
This fixes it by adjusting the "kernel_msr" value in the PACA so that
it only has MSR_IR and MSR_DR (translation for instruction and data)
set after the MMU has been initialized for the processor.
We may still not have a console yet but at least we don't get into
a recursive fault (and early debug console or memory dump via JTAG
of the kernel buffer *will* give us the proper error).
Signed-off-by: Benjamin Herrenschmidt <b...@kernel.crashing.org>
---
arch/powerpc/kernel/paca.c | 3 ++-
arch/powerpc/kernel/setup_64.c | 15 +++++++++++++++
2 files changed, 17 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/kernel/paca.c b/arch/powerpc/kernel/paca.c
index bf0aada..ad302f8 100644
--- a/arch/powerpc/kernel/paca.c
+++ b/arch/powerpc/kernel/paca.c
@@ -152,7 +152,8 @@ void __init initialise_paca(struct paca_struct *new_paca,
int cpu)
new_paca->paca_index = cpu;
new_paca->kernel_toc = kernel_toc;
new_paca->kernelbase = (unsigned long) _stext;
- new_paca->kernel_msr = MSR_KERNEL;
+ /* Only set MSR:IR/DR when MMU is initialized */
+ new_paca->kernel_msr = MSR_KERNEL & ~(MSR_IR | MSR_DR);
new_paca->hw_cpu_id = 0xffff;
new_paca->kexec_state = KEXEC_STATE_NONE;
new_paca->__current = &init_task;
diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index d8aabbd..1d33e81 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -261,6 +261,14 @@ void __init early_setup(unsigned long dt_ptr)
/* Initialize the hash table or TLB handling */
early_init_mmu();
+ /*
+ * At this point, we can let interrupts switch to virtual mode
+ * (the MMU has been setup), so adjust the MSR in the PACA to
+ * have IR and DR set.
+ */
+ get_paca()->kernel_msr = MSR_KERNEL;
+
+ /* Reserve large chunks of memory for use by CMA for KVM */
kvm_cma_reserve();
/*
@@ -293,6 +301,13 @@ void early_setup_secondary(void)
/* Initialize the hash table or TLB handling */
early_init_mmu_secondary();
+
+ /*
+ * At this point, we can let interrupts switch to virtual mode
+ * (the MMU has been setup), so adjust the MSR in the PACA to
+ * have IR and DR set.
+ */
+ get_paca()->kernel_msr = MSR_KERNEL;
}
#endif /* CONFIG_SMP */
--
1.8.3.2
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