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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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75370ad440
Commit4255b07f2c("ARCv2: STAR 9000793984: Handle return from intr to Delay Slot") involved a complex 2 staged trampoline. Apparently this can be greatly simplified by returning from pure kernel mode (iso interrupt) so drop to pure kernel mdoe and execute the normal exception return path. Testing this was a bit of challenge as return from interrupt is rarely executed now after commit4de0e52867("ARCv2: STAR 9000814690: Really Re-enable interrupts to avoid deadlocks"). That fix is necessary evil and pct interrupts etc do exercise intr return path. Anyhow after a revert of above in my local test setup I was able to hit this case and verify the patch works. Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
264 lines
7.1 KiB
ArmAsm
264 lines
7.1 KiB
ArmAsm
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* ARCv2 ISA based core Low Level Intr/Traps/Exceptions(non-TLB) Handling
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*
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* Copyright (C) 2013 Synopsys, Inc. (www.synopsys.com)
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*/
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#include <linux/linkage.h> /* ARC_{EXTRY,EXIT} */
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#include <asm/entry.h> /* SAVE_ALL_{INT1,INT2,TRAP...} */
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#include <asm/errno.h>
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#include <asm/arcregs.h>
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#include <asm/irqflags.h>
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; A maximum number of supported interrupts in the core interrupt controller.
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; This number is not equal to the maximum interrupt number (256) because
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; first 16 lines are reserved for exceptions and are not configurable.
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#define NR_CPU_IRQS 240
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.cpu HS
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#define VECTOR .word
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;############################ Vector Table #################################
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.section .vector,"a",@progbits
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.align 4
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# Initial 16 slots are Exception Vectors
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VECTOR res_service ; Reset Vector
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VECTOR mem_service ; Mem exception
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VECTOR instr_service ; Instrn Error
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VECTOR EV_MachineCheck ; Fatal Machine check
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VECTOR EV_TLBMissI ; Intruction TLB miss
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VECTOR EV_TLBMissD ; Data TLB miss
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VECTOR EV_TLBProtV ; Protection Violation
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VECTOR EV_PrivilegeV ; Privilege Violation
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VECTOR EV_SWI ; Software Breakpoint
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VECTOR EV_Trap ; Trap exception
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VECTOR EV_Extension ; Extn Instruction Exception
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VECTOR EV_DivZero ; Divide by Zero
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VECTOR EV_DCError ; Data Cache Error
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VECTOR EV_Misaligned ; Misaligned Data Access
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VECTOR reserved ; Reserved slots
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VECTOR reserved ; Reserved slots
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# Begin Interrupt Vectors
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VECTOR handle_interrupt ; (16) Timer0
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VECTOR handle_interrupt ; unused (Timer1)
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VECTOR handle_interrupt ; unused (WDT)
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VECTOR handle_interrupt ; (19) Inter core Interrupt (IPI)
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VECTOR handle_interrupt ; (20) perf Interrupt
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VECTOR handle_interrupt ; (21) Software Triggered Intr (Self IPI)
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VECTOR handle_interrupt ; unused
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VECTOR handle_interrupt ; (23) unused
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# End of fixed IRQs
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.rept NR_CPU_IRQS - 8
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VECTOR handle_interrupt
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.endr
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.section .text, "ax",@progbits
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reserved:
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flag 1 ; Unexpected event, halt
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;##################### Interrupt Handling ##############################
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ENTRY(handle_interrupt)
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INTERRUPT_PROLOGUE
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# irq control APIs local_irq_save/restore/disable/enable fiddle with
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# global interrupt enable bits in STATUS32 (.IE for 1 prio, .E[] for 2 prio)
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# However a taken interrupt doesn't clear these bits. Thus irqs_disabled()
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# query in hard ISR path would return false (since .IE is set) which would
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# trips genirq interrupt handling asserts.
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#
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# So do a "soft" disable of interrutps here.
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#
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# Note this disable is only for consistent book-keeping as further interrupts
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# will be disabled anyways even w/o this. Hardware tracks active interrupts
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# seperately in AUX_IRQ_ACT.active and will not take new interrupts
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# unless this one returns (or higher prio becomes pending in 2-prio scheme)
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IRQ_DISABLE
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; icause is banked: one per priority level
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; so a higher prio interrupt taken here won't clobber prev prio icause
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lr r0, [ICAUSE]
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mov blink, ret_from_exception
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b.d arch_do_IRQ
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mov r1, sp
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END(handle_interrupt)
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;################### Non TLB Exception Handling #############################
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ENTRY(EV_SWI)
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; TODO: implement this
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EXCEPTION_PROLOGUE
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b ret_from_exception
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END(EV_SWI)
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ENTRY(EV_DivZero)
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; TODO: implement this
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EXCEPTION_PROLOGUE
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b ret_from_exception
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END(EV_DivZero)
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ENTRY(EV_DCError)
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; TODO: implement this
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EXCEPTION_PROLOGUE
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b ret_from_exception
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END(EV_DCError)
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; ---------------------------------------------
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; Memory Error Exception Handler
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; - Unlike ARCompact, handles Bus errors for both User/Kernel mode,
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; Instruction fetch or Data access, under a single Exception Vector
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; ---------------------------------------------
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ENTRY(mem_service)
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EXCEPTION_PROLOGUE
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lr r0, [efa]
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mov r1, sp
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FAKE_RET_FROM_EXCPN
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bl do_memory_error
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b ret_from_exception
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END(mem_service)
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ENTRY(EV_Misaligned)
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EXCEPTION_PROLOGUE
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lr r0, [efa] ; Faulting Data address
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mov r1, sp
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FAKE_RET_FROM_EXCPN
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SAVE_CALLEE_SAVED_USER
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mov r2, sp ; callee_regs
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bl do_misaligned_access
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; TBD: optimize - do this only if a callee reg was involved
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; either a dst of emulated LD/ST or src with address-writeback
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RESTORE_CALLEE_SAVED_USER
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b ret_from_exception
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END(EV_Misaligned)
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; ---------------------------------------------
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; Protection Violation Exception Handler
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; ---------------------------------------------
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ENTRY(EV_TLBProtV)
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EXCEPTION_PROLOGUE
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lr r0, [efa] ; Faulting Data address
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mov r1, sp ; pt_regs
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FAKE_RET_FROM_EXCPN
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mov blink, ret_from_exception
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b do_page_fault
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END(EV_TLBProtV)
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; From Linux standpoint Slow Path I/D TLB Miss is same a ProtV as they
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; need to call do_page_fault().
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; ECR in pt_regs provides whether access was R/W/X
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.global call_do_page_fault
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.set call_do_page_fault, EV_TLBProtV
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;############# Common Handlers for ARCompact and ARCv2 ##############
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#include "entry.S"
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;############# Return from Intr/Excp/Trap (ARCv2 ISA Specifics) ##############
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;
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; Restore the saved sys context (common exit-path for EXCPN/IRQ/Trap)
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; IRQ shd definitely not happen between now and rtie
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; All 2 entry points to here already disable interrupts
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.Lrestore_regs:
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restore_regs:
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# Interrpts are actually disabled from this point on, but will get
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# reenabled after we return from interrupt/exception.
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# But irq tracer needs to be told now...
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TRACE_ASM_IRQ_ENABLE
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ld r0, [sp, PT_status32] ; U/K mode at time of entry
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lr r10, [AUX_IRQ_ACT]
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bmsk r11, r10, 15 ; extract AUX_IRQ_ACT.active
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breq r11, 0, .Lexcept_ret ; No intr active, ret from Exception
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;####### Return from Intr #######
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.Lisr_ret:
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debug_marker_l1:
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; bbit1.nt r0, STATUS_DE_BIT, .Lintr_ret_to_delay_slot
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btst r0, STATUS_DE_BIT ; Z flag set if bit clear
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bnz .Lintr_ret_to_delay_slot ; branch if STATUS_DE_BIT set
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; Handle special case #1: (Entry via Exception, Return via IRQ)
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;
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; Exception in U mode, preempted in kernel, Intr taken (K mode), orig
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; task now returning to U mode (riding the Intr)
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; AUX_IRQ_ACTIVE won't have U bit set (since intr in K mode), hence SP
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; won't be switched to correct U mode value (from AUX_SP)
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; So force AUX_IRQ_ACT.U for such a case
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btst r0, STATUS_U_BIT ; Z flag set if K (Z clear for U)
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bset.nz r11, r11, AUX_IRQ_ACT_BIT_U ; NZ means U
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sr r11, [AUX_IRQ_ACT]
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INTERRUPT_EPILOGUE
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rtie
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;####### Return from Exception / pure kernel mode #######
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.Lexcept_ret: ; Expects r0 has PT_status32
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debug_marker_syscall:
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EXCEPTION_EPILOGUE
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rtie
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;####### Return from Intr to insn in delay slot #######
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; Handle special case #2: (Entry via Exception in Delay Slot, Return via IRQ)
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;
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; Intr returning to a Delay Slot (DS) insn
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; (since IRQ NOT allowed in DS in ARCv2, this can only happen if orig
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; entry was via Exception in DS which got preempted in kernel).
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;
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; IRQ RTIE won't reliably restore DE bit and/or BTA, needs workaround
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;
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; Solution is to drop out of interrupt context into pure kernel mode
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; and return from pure kernel mode which does right things for delay slot
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.Lintr_ret_to_delay_slot:
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debug_marker_ds:
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ld r2, [@intr_to_DE_cnt]
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add r2, r2, 1
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st r2, [@intr_to_DE_cnt]
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; drop out of interrupt context (clear AUX_IRQ_ACT.active)
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bmskn r11, r10, 15
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sr r11, [AUX_IRQ_ACT]
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b .Lexcept_ret
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END(ret_from_exception)
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