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>
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@ -152,7 +152,8 @@ void __init initialise_paca(struct paca_struct *new_paca, int cpu)
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new_paca->paca_index = cpu;
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new_paca->kernel_toc = kernel_toc;
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new_paca->kernelbase = (unsigned long) _stext;
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new_paca->kernel_msr = MSR_KERNEL;
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/* Only set MSR:IR/DR when MMU is initialized */
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new_paca->kernel_msr = MSR_KERNEL & ~(MSR_IR | MSR_DR);
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new_paca->hw_cpu_id = 0xffff;
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new_paca->kexec_state = KEXEC_STATE_NONE;
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new_paca->__current = &init_task;
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@ -261,6 +261,14 @@ void __init early_setup(unsigned long dt_ptr)
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/* Initialize the hash table or TLB handling */
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early_init_mmu();
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/*
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* At this point, we can let interrupts switch to virtual mode
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* (the MMU has been setup), so adjust the MSR in the PACA to
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* have IR and DR set.
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*/
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get_paca()->kernel_msr = MSR_KERNEL;
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/* Reserve large chunks of memory for use by CMA for KVM */
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kvm_cma_reserve();
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/*
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@ -293,6 +301,13 @@ void early_setup_secondary(void)
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/* Initialize the hash table or TLB handling */
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early_init_mmu_secondary();
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/*
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* At this point, we can let interrupts switch to virtual mode
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* (the MMU has been setup), so adjust the MSR in the PACA to
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* have IR and DR set.
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*/
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get_paca()->kernel_msr = MSR_KERNEL;
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}
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#endif /* CONFIG_SMP */
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