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powerpc/ppc64: Gracefully handle early interrupts

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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>
This commit is contained in:
Benjamin Herrenschmidt 2014-03-28 13:36:29 +11:00
parent 7222f779ac
commit a944a9c40b
2 changed files with 17 additions and 1 deletions
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3
arch/powerpc/kernel/paca.c
View File

@ -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;

15
arch/powerpc/kernel/setup_64.c
View File

@ -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 */