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Commit a944a9c4 authored by Benjamin Herrenschmidt's avatar Benjamin Herrenschmidt
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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: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent 7222f779

arch/powerpc/kernel/paca.c

+2 −1
Original line number Diff line number Diff line
@@ -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;

arch/powerpc/kernel/setup_64.c

+15 −0
Original line number Diff line number Diff line
@@ -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 */