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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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1e9b4507ed
Move machine check entry point into Linux. So far we were dependent on firmware to decode MCE error details and handover the high level info to OS. This patch introduces early machine check routine that saves the MCE information (srr1, srr0, dar and dsisr) to the emergency stack. We allocate stack frame on emergency stack and set the r1 accordingly. This allows us to be prepared to take another exception without loosing context. One thing to note here that, if we get another machine check while ME bit is off then we risk a checkstop. Hence we restrict ourselves to save only MCE information and register saved on PACA_EXMC save are before we turn the ME bit on. We use paca->in_mce flag to differentiate between first entry and nested machine check entry which helps proper use of emergency stack. We increment paca->in_mce every time we enter in early machine check handler and decrement it while leaving. When we enter machine check early handler first time (paca->in_mce == 0), we are sure nobody is using MC emergency stack and allocate a stack frame at the start of the emergency stack. During subsequent entry (paca->in_mce > 0), we know that r1 points inside emergency stack and we allocate separate stack frame accordingly. This prevents us from clobbering MCE information during nested machine checks. The early machine check handler changes are placed under CPU_FTR_HVMODE section. This makes sure that the early machine check handler will get executed only in hypervisor kernel. This is the code flow: Machine Check Interrupt | V 0x200 vector ME=0, IR=0, DR=0 | V +-----------------------------------------------+ |machine_check_pSeries_early: | ME=0, IR=0, DR=0 | Alloc frame on emergency stack | | Save srr1, srr0, dar and dsisr on stack | +-----------------------------------------------+ | (ME=1, IR=0, DR=0, RFID) | V machine_check_handle_early ME=1, IR=0, DR=0 | V +-----------------------------------------------+ | machine_check_early (r3=pt_regs) | ME=1, IR=0, DR=0 | Things to do: (in next patches) | | Flush SLB for SLB errors | | Flush TLB for TLB errors | | Decode and save MCE info | +-----------------------------------------------+ | (Fall through existing exception handler routine.) | V machine_check_pSerie ME=1, IR=0, DR=0 | (ME=1, IR=1, DR=1, RFID) | V machine_check_common ME=1, IR=1, DR=1 . . . Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> |
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