Re: [Qemu-devel] [PATCH V8 2/7] nios2: Add architecture emulation support

[Alexander Graf]

> Am 17.01.2017 um 01:18 schrieb Marek Vasut <address@hidden>:
> 
>> On 01/16/2017 11:21 PM, Alexander Graf wrote:
>> 
>> 
>>> On 31/12/2016 14:22, Marek Vasut wrote:
>>> From: Chris Wulff <address@hidden>
>>> 
>>> Add support for emulating Altera NiosII R1 architecture into qemu.
>>> This patch is based on previous work by Chris Wulff from 2012 and
>>> updated to latest mainline QEMU.
>>> 
>>> Signed-off-by: Marek Vasut <address@hidden>
>>> Cc: Chris Wulff <address@hidden>
>>> Cc: Jeff Da Silva <address@hidden>
>>> Cc: Ley Foon Tan <address@hidden>
>>> Cc: Sandra Loosemore <address@hidden>
>>> Cc: Yves Vandervennet <address@hidden>
>>> ---
>>> V3: Thorough cleanup, deal with the review comments all over the place
>>> V4: - Use extract32()
>>>    - Fix gen_goto_tb() , suppress tcg_gen_goto_tb()
>>>    - Clean up gen_check_supervisor() helper
>>>    - Use TCGMemOp type for flags
>>>    - Drop jump labels from wrctl/rdctl
>>>    - More TCG cleanup
>>> V5: - Simplify load/store handling
>>>    - Handle loads into R_ZERO from protected page, add comment
>>> V6: - Fix division opcode handling
>>>    - Add missing disas handling
>>>    - V5 review comments cleanup
>>> V7: - Drop newline at the end of file
>>> V8: - Rebase on top of qemu/master
>>>    - Move the target-nios2 to target/nios2
>>> ---
>>> target/nios2/Makefile.objs |   4 +
>>> target/nios2/cpu.c         | 232 +++++++++++
>>> target/nios2/cpu.h         | 269 +++++++++++++
>>> target/nios2/helper.c      | 313 +++++++++++++++
>>> target/nios2/helper.h      |  27 ++
>>> target/nios2/mmu.c         | 292 ++++++++++++++
>>> target/nios2/mmu.h         |  54 +++
>>> target/nios2/monitor.c     |  35 ++
>>> target/nios2/op_helper.c   |  47 +++
>>> target/nios2/translate.c   | 953
>>> +++++++++++++++++++++++++++++++++++++++++++++
>>> 10 files changed, 2226 insertions(+)
>>> create mode 100644 target/nios2/Makefile.objs
>>> create mode 100644 target/nios2/cpu.c
>>> create mode 100644 target/nios2/cpu.h
>>> create mode 100644 target/nios2/helper.c
>>> create mode 100644 target/nios2/helper.h
>>> create mode 100644 target/nios2/mmu.c
>>> create mode 100644 target/nios2/mmu.h
>>> create mode 100644 target/nios2/monitor.c
>>> create mode 100644 target/nios2/op_helper.c
>>> create mode 100644 target/nios2/translate.c
>>> 
>>> diff --git a/target/nios2/Makefile.objs b/target/nios2/Makefile.objs
>>> new file mode 100644
>>> index 0000000..2a11c5c
>>> --- /dev/null
>>> +++ b/target/nios2/Makefile.objs
>>> @@ -0,0 +1,4 @@
>>> +obj-y += translate.o op_helper.o helper.o cpu.o mmu.o
>>> +obj-$(CONFIG_SOFTMMU) += monitor.o
>>> +
>>> +$(obj)/op_helper.o: QEMU_CFLAGS += $(HELPER_CFLAGS)
>>> diff --git a/target/nios2/cpu.c b/target/nios2/cpu.c
>>> new file mode 100644
>>> index 0000000..658d684
>>> --- /dev/null
>>> +++ b/target/nios2/cpu.c
>>> @@ -0,0 +1,232 @@
>>> +/*
>>> + * QEMU Nios II CPU
>>> + *
>>> + * Copyright (c) 2012 Chris Wulff <address@hidden>
>>> + *
>>> + * This library is free software; you can redistribute it and/or
>>> + * modify it under the terms of the GNU Lesser General Public
>>> + * License as published by the Free Software Foundation; either
>>> + * version 2.1 of the License, or (at your option) any later version.
>>> + *
>>> + * This library is distributed in the hope that it will be useful,
>>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>>> + * Lesser General Public License for more details.
>>> + *
>>> + * You should have received a copy of the GNU Lesser General Public
>>> + * License along with this library; if not, see
>>> + * <http://www.gnu.org/licenses/lgpl-2.1.html>
>>> + */
>>> +
>>> +#include "qemu/osdep.h"
>>> +#include "qemu-common.h"
>>> +#include "qapi/error.h"
>>> +#include "cpu.h"
>>> +#include "exec/log.h"
>>> +#include "exec/gdbstub.h"
>>> +#include "hw/qdev-properties.h"
>>> +
>>> +static void nios2_cpu_set_pc(CPUState *cs, vaddr value)
>>> +{
>>> +    Nios2CPU *cpu = NIOS2_CPU(cs);
>>> +    CPUNios2State *env = &cpu->env;
>>> +
>>> +    env->regs[R_PC] = value;
>>> +}
>>> +
>>> +static bool nios2_cpu_has_work(CPUState *cs)
>>> +{
>>> +    return cs->interrupt_request & (CPU_INTERRUPT_HARD |
>>> CPU_INTERRUPT_NMI);
>>> +}
>>> +
>>> +/* CPUClass::reset() */
>>> +static void nios2_cpu_reset(CPUState *cs)
>>> +{
>>> +    Nios2CPU *cpu = NIOS2_CPU(cs);
>>> +    Nios2CPUClass *ncc = NIOS2_CPU_GET_CLASS(cpu);
>>> +    CPUNios2State *env = &cpu->env;
>>> +
>>> +    if (qemu_loglevel_mask(CPU_LOG_RESET)) {
>>> +        qemu_log("CPU Reset (CPU %d)\n", cs->cpu_index);
>>> +        log_cpu_state(cs, 0);
>>> +    }
>>> +
>>> +    ncc->parent_reset(cs);
>>> +
>>> +    tlb_flush(cs, 1);
>>> +
>>> +    memset(env->regs, 0, sizeof(uint32_t) * NUM_CORE_REGS);
>>> +    env->regs[R_PC] = cpu->reset_addr;
>>> +
>>> +#if defined(CONFIG_USER_ONLY)
>>> +    /* Start in user mode with interrupts enabled. */
>>> +    env->regs[CR_STATUS] = CR_STATUS_U | CR_STATUS_PIE;
>> 
>> So what is the value of CR_STATUS after reset in softmmu land then?
>> Random value from before reset? Probably not what you want :).
> 
> Dropped, yeah.

Dropped? That wasn't my intention :).

I was just too tired to grasp the code. CR_STATUS is 0 for softmmu thanks to 
the memset, so irqs are disabled. For linux-user, applications expect irqs to 
work, so it needs to be explicitly set to on.

The code above is perfectly correct I think.


Alex