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From:   "Ofer Levi(SW)" <oferle@mellanox.com>
To:     "vgupta@synopsys.com" <vgupta@synopsys.com>
CC:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "Meir Lichtinger" <meirl@mellanox.com>
Subject: RE: ARC compact700 NPS platform - EZ_MachineCheck exception handler
Thread-Topic: ARC compact700 NPS platform - EZ_MachineCheck exception handler
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Date:   Mon, 21 May 2018 14:14:38 +0000
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 Hi Vineet,
=20
 The EV_MachineCheck exception handler is halting the core for exceptions
 which are not tlb_overlap_fault.
 Since for the NPS platform each core is running a single thread in ZOL (Ze=
ro
 Overhead Linux) isolation mode, we feel that most of the time it is safe t=
o
 resume execution instead of halting the core.
 I would appreciate it if you could review the change  below and let me kno=
w
 what you think, if this change is valid or if we missed or overlooked
 something.
 We are not looking to push this change upstream, but will be used on some
 systems.
=20
 Please see below our implementation after label 1.
=20
 Thanks
 Ofer
=20
 ENTRY(EV_MachineCheck)
=20
 	EXCEPTION_PROLOGUE
=20
 #ifdef CONFIG_CONTEXT_TRACKING
 	bl context_tracking_user_exit
 #endif
=20
 	lr  r2, [ecr]
 	lr  r0, [efa]
 	mov r1, sp
=20
 	; hardware auto-disables MMU, re-enable it to allow kernel vaddr
 	; access for say stack unwinding of modules for crash dumps
 	lr r3, [ARC_REG_PID]
 	or r3, r3, MMU_ENABLE
 	sr r3, [ARC_REG_PID]
=20
 	lsr  	r3, r2, 8
 	bmsk 	r3, r3, 7
 	brne    r3, ECR_C_MCHK_DUP_TLB, 1f
=20
 	bl      do_tlb_overlap_fault
 	b       ret_from_exception
=20
 1:
 	FAKE_RET_FROM_EXCPN
 	bl		do_machine_check  ; using DO_ERROR_INFO macro
 	b       ret_from_exception
=20
 END(EV_MachineCheck)