powerpc/ppc64: Gracefully handle early interrupts
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 <benh@kernel.crashing.org>
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 @@
/* 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 @@
/* 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 */