Re: [Qemu-devel] [PATCH 5/6] [RFC] Emulation of Leon3.

[Blue Swirl]

On Mon, Dec 13, 2010 at 3:51 PM, Fabien Chouteau <address@hidden> wrote:
> On 12/11/2010 10:56 AM, Blue Swirl wrote:
>>
>> On Tue, Dec 7, 2010 at 11:40 AM, Fabien Chouteau<address@hidden>
>>  wrote:
>>>
>>> On 12/06/2010 06:53 PM, Blue Swirl wrote:
>>>>
>>>> On Mon, Dec 6, 2010 at 9:26 AM, Fabien Chouteau<address@hidden>
>>>>  wrote:
>>>>>
>>>>> Signed-off-by: Fabien Chouteau<address@hidden>
>>>>> ---
>>>>>  Makefile.target          |    5 +-
>>>>>  hw/leon3.c               |  310
>>>>> ++++++++++++++++++++++++++++++++++++++++++++++
>>>>>  target-sparc/cpu.h       |   10 ++
>>>>>  target-sparc/helper.c    |    2 +-
>>>>>  target-sparc/op_helper.c |   30 ++++-
>>>>>  5 files changed, 353 insertions(+), 4 deletions(-)
>>>>>
>>>>> diff --git a/Makefile.target b/Makefile.target
>>>>> index 2800f47..f40e04f 100644
>>>>> --- a/Makefile.target
>>>>> +++ b/Makefile.target
>>>>> @@ -290,7 +290,10 @@ obj-sparc-y += cirrus_vga.o
>>>>>  else
>>>>>  obj-sparc-y = sun4m.o lance.o tcx.o sun4m_iommu.o slavio_intctl.o
>>>>>  obj-sparc-y += slavio_timer.o slavio_misc.o sparc32_dma.o
>>>>> -obj-sparc-y += cs4231.o eccmemctl.o sbi.o sun4c_intctl.o
>>>>> +obj-sparc-y += cs4231.o eccmemctl.o sbi.o sun4c_intctl.o leon3.o
>>>>> +
>>>>> +# GRLIB
>>>>> +obj-sparc-y += grlib_gptimer.o grlib_irqmp.o grlib_apbuart.o
>>>>>  endif
>>>>>
>>>>>  obj-arm-y = integratorcp.o versatilepb.o arm_pic.o arm_timer.o
>>>>> diff --git a/hw/leon3.c b/hw/leon3.c
>>>>> new file mode 100644
>>>>> index 0000000..ba61081
>>>>> --- /dev/null
>>>>> +++ b/hw/leon3.c
>>>>> @@ -0,0 +1,310 @@
>>>>> +/*
>>>>> + * QEMU Leon3 System Emulator
>>>>> + *
>>>>> + * Copyright (c) 2010 AdaCore
>>>>> + *
>>>>> + * Permission is hereby granted, free of charge, to any person
>>>>> obtaining
>>>>> a copy
>>>>> + * of this software and associated documentation files (the
>>>>> "Software"),
>>>>> to deal
>>>>> + * in the Software without restriction, including without limitation
>>>>> the
>>>>> rights
>>>>> + * to use, copy, modify, merge, publish, distribute, sublicense,
>>>>> and/or
>>>>> sell
>>>>> + * copies of the Software, and to permit persons to whom the Software
>>>>> is
>>>>> + * furnished to do so, subject to the following conditions:
>>>>> + *
>>>>> + * The above copyright notice and this permission notice shall be
>>>>> included in
>>>>> + * all copies or substantial portions of the Software.
>>>>> + *
>>>>> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
>>>>> EXPRESS OR
>>>>> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
>>>>> MERCHANTABILITY,
>>>>> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
>>>>> SHALL
>>>>> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES
>>>>> OR
>>>>> OTHER
>>>>> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
>>>>> ARISING FROM,
>>>>> + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
>>>>> DEALINGS IN
>>>>> + * THE SOFTWARE.
>>>>> + */
>>>>> +#include "hw.h"
>>>>> +#include "qemu-timer.h"
>>>>> +#include "qemu-char.h"
>>>>> +#include "sysemu.h"
>>>>> +#include "boards.h"
>>>>> +#include "loader.h"
>>>>> +#include "elf.h"
>>>>> +
>>>>> +#include "grlib.h"
>>>>> +
>>>>> +/* #define DEBUG_LEON3 */
>>>>> +
>>>>> +#ifdef DEBUG_LEON3
>>>>> +#define DPRINTF(fmt, ...)                                       \
>>>>> +    do { printf("Leon3: " fmt , ## __VA_ARGS__); } while (0)
>>>>> +#else
>>>>> +#define DPRINTF(fmt, ...)
>>>>> +#endif
>>>>> +
>>>>> +/* Default system clock.  */
>>>>> +#define CPU_CLK (40 * 1000 * 1000)
>>>>> +
>>>>> +#define PROM_FILENAME        "u-boot.bin"
>>>>> +
>>>>> +#define MAX_PILS 16
>>>>> +
>>>>> +typedef struct Leon3State
>>>>> +{
>>>>> +    uint32_t cache_control;
>>>>> +    uint32_t inst_cache_conf;
>>>>> +    uint32_t data_cache_conf;
>>>>> +
>>>>> +    uint64_t entry;             /* save kernel entry in case of reset
>>>>> */
>>>>> +} Leon3State;
>>>>> +
>>>>> +Leon3State leon3_state;
>>>>
>>>> Again global state, please refactor. Perhaps most of the cache
>>>> handling code belong to target-sparc/op_helper.c and this structure to
>>>> CPUSPARCState.
>>>
>>> I will try to find a solution for that.
>>> Is it OK to add some Leon3 specific stuff in the CPUSPARCState?
>>
>> Yes, no problem. You can also drop the intermediate Leon3State
>> structure if there is no benefit.
>>
>>>>> +
>>>>> +/* Cache control: emulate the behavior of cache control registers but
>>>>> without
>>>>> +   any effect on the emulated CPU */
>>>>> +
>>>>> +#define CACHE_DISABLED 0x0
>>>>> +#define CACHE_FROZEN   0x1
>>>>> +#define CACHE_ENABLED  0x3
>>>>> +
>>>>> +/* Cache Control register fields */
>>>>> +
>>>>> +#define CACHE_CTRL_IF (1<<      4)  /* Instruction Cache Freeze on
>>>>> Interrupt */
>>>>> +#define CACHE_CTRL_DF (1<<      5)  /* Data Cache Freeze on Interrupt
>>>>> */
>>>>> +#define CACHE_CTRL_DP (1<<    14)  /* Data cache flush pending */
>>>>> +#define CACHE_CTRL_IP (1<<    15)  /* Instruction cache flush pending
>>>>> */
>>>>> +#define CACHE_CTRL_IB (1<<    16)  /* Instruction burst fetch */
>>>>> +#define CACHE_CTRL_FI (1<<    21)  /* Flush Instruction cache (Write
>>>>> only)
>>>>> */
>>>>> +#define CACHE_CTRL_FD (1<<    22)  /* Flush Data cache (Write only) */
>>>>> +#define CACHE_CTRL_DS (1<<    23)  /* Data cache snoop enable */
>>>>> +
>>>>> +void leon3_cache_control_int(void)
>>>>> +{
>>>>> +    uint32_t state = 0;
>>>>> +
>>>>> +    if (leon3_state.cache_control&    CACHE_CTRL_IF) {
>>>>> +        /* Instruction cache state */
>>>>> +        state = leon3_state.cache_control&    0x3;
>>>>
>>>> Please add a new define CACHE_CTRL_xxx to replace 0x3.
>>>>
>>>
>>> Done.
>>>
>>>>> +        if (state == CACHE_ENABLED) {
>>>>> +            state = CACHE_FROZEN;
>>>>> +            DPRINTF("Instruction cache: freeze\n");
>>>>> +        }
>>>>> +
>>>>> +        leon3_state.cache_control&= ~0x3;
>>>>> +        leon3_state.cache_control |= state;
>>>>> +    }
>>>>> +
>>>>> +    if (leon3_state.cache_control&    CACHE_CTRL_DF) {
>>>>> +        /* Data cache state */
>>>>> +        state = (leon3_state.cache_control>>    2)&    0x3;
>>>>> +        if (state == CACHE_ENABLED) {
>>>>> +            state = CACHE_FROZEN;
>>>>> +            DPRINTF("Data cache: freeze\n");
>>>>> +        }
>>>>> +
>>>>> +        leon3_state.cache_control&= ~(0x3<<    2);
>>>>> +        leon3_state.cache_control |= (state<<    2);
>>>>> +    }
>>>>> +}
>>>>> +
>>>>> +void leon3_cache_control_st(target_ulong addr, uint64_t val, int size)
>>>>> +{
>>>>> +    DPRINTF("cc st addr:%lu, val:0x%x, size:%d\n", (long unsigned
>>>>> int)addr,
>>>>> +            (unsigned int)val, size);
>>>>
>>>> There's PRIx64 to print uint64_t portably, then the casts can be
>>>> removed.
>>>>
>>>
>>> Fixed.
>>>
>>>>> +
>>>>> +    if (size != 4) {
>>>>> +        DPRINTF(" CC 32bits only\n");
>>>>> +        return;
>>>>> +    }
>>>>> +
>>>>> +    switch (addr) {
>>>>> +        case 0x00:              /* Cache control */
>>>>> +
>>>>> +            /* These values must always be read as zeros */
>>>>> +            val&= ~CACHE_CTRL_FD;
>>>>> +            val&= ~CACHE_CTRL_FI;
>>>>> +            val&= ~CACHE_CTRL_IB;
>>>>> +            val&= ~CACHE_CTRL_IP;
>>>>> +            val&= ~CACHE_CTRL_DP;
>>>>> +
>>>>> +            leon3_state.cache_control = val;
>>>>> +            break;
>>>>> +        case 0x04:              /* Instruction cache configuration */
>>>>> +        case 0x08:              /* Data cache configuration */
>>>>> +            /* Read Only */
>>>>> +            break;
>>>>> +        default:
>>>>> +            DPRINTF(" CC write unknown register 0x%04x\n", (int)addr);
>>>>> +            break;
>>>>> +    };
>>>>> +}
>>>>> +
>>>>> +uint64_t leon3_cache_control_ld(target_ulong addr, int size)
>>>>> +{
>>>>> +    uint64_t ret = 0;
>>>>> +
>>>>> +    if (size != 4) {
>>>>> +        DPRINTF(" CC 32bits only\n");
>>>>> +        return 0;
>>>>> +    }
>>>>> +
>>>>> +    switch (addr) {
>>>>> +        case 0x00:              /* Cache control */
>>>>> +            ret = leon3_state.cache_control;
>>>>> +            break;
>>>>> +        case 0x04:              /* Instruction cache configuration */
>>>>> +            ret = leon3_state.inst_cache_conf;
>>>>> +            break;
>>>>> +        case 0x08:              /* Data cache configuration */
>>>>> +            ret = leon3_state.data_cache_conf;
>>>>> +            break;
>>>>> +        default:
>>>>> +            DPRINTF(" CC read unknown register 0x%04x\n", (int)addr);
>>>>> +            break;
>>>>> +    };
>>>>> +    DPRINTF("cc ld addr:%lu, size:%d, ret:%lu\n", (long unsigned
>>>>> int)addr,
>>>>> +            size, (long unsigned int)ret );
>>>>> +    return ret;
>>>>> +}
>>>>> +
>>>>> +void leon3_shutdown(void)
>>>>> +{
>>>>> +    qemu_system_shutdown_request();
>>>>> +}
>>>>> +
>>>>> +static void main_cpu_reset(void *opaque)
>>>>> +{
>>>>> +    CPUState *env = opaque;
>>>>
>>>> Here you can introduce a helper structure to pass PC and NPC, like
>>>> sun4u.c ResetData. Then the global state should not be needed anymore.
>>>>
>>>
>>> OK, I've used the sun4u.c reset scheme.
>>>
>>>>> +
>>>>> +    cpu_reset(env);
>>>>> +
>>>>> +    env->halted = 0;
>>>>> +    env->pc     = leon3_state.entry;
>>>>> +    env->npc    = leon3_state.entry + 4;
>>>>> +
>>>>> +    /* Initialize cache control */
>>>>> +    leon3_state.cache_control   = 0x0;
>>>>> +
>>>>> +    /* Configuration registers are read and only always keep those
>>>>> predefined
>>>>> +       values */
>>>>> +    leon3_state.inst_cache_conf = 0x10220000;
>>>>> +    leon3_state.data_cache_conf = 0x18220000;
>>>>> +}
>>>>> +
>>>>> +static void leon3_generic_hw_init(ram_addr_t  ram_size,
>>>>> +                                  const char *boot_device,
>>>>> +                                  const char *kernel_filename,
>>>>> +                                  const char *kernel_cmdline,
>>>>> +                                  const char *initrd_filename,
>>>>> +                                  const char *cpu_model)
>>>>> +{
>>>>> +    CPUState   *env;
>>>>> +    ram_addr_t  ram_offset, prom_offset;
>>>>> +    int         ret;
>>>>> +    char       *filename;
>>>>> +    qemu_irq   *cpu_irqs = NULL;
>>>>> +    int         bios_size;
>>>>> +    int         prom_size;
>>>>> +    int         aligned_bios_size;
>>>>> +
>>>>> +    /* Init CPU */
>>>>> +    if (!cpu_model)
>>>>> +        cpu_model = "LEON3";
>>>>
>>>> Missing braces.
>>>
>>> Fixed.
>>>
>>>>
>>>>> +
>>>>> +    env = cpu_init(cpu_model);
>>>>> +    if (!env) {
>>>>> +        fprintf(stderr, "qemu: Unable to find Sparc CPU
>>>>> definition\n");
>>>>> +        exit(1);
>>>>> +    }
>>>>> +
>>>>> +    cpu_sparc_set_id(env, 0);
>>>>> +
>>>>> +    qemu_register_reset(main_cpu_reset, env);
>>>>> +
>>>>> +    /* Allocate IRQ manager */
>>>>> +    grlib_irqmp_create(0x80000200, env,&cpu_irqs, MAX_PILS);
>>>>> +
>>>>> +    /* Allocate RAM */
>>>>> +    if ((uint64_t)ram_size>    (1UL<<    30)) {
>>>>> +        fprintf(stderr,
>>>>> +                "qemu: Too much memory for this machine: %d, maximum
>>>>> 1G\n",
>>>>> +                (unsigned int)(ram_size / (1024 * 1024)));
>>>>> +        exit(1);
>>>>> +    }
>>>>> +
>>>>> +    ram_offset = qemu_ram_alloc(NULL, "leon3.ram", ram_size);
>>>>> +    cpu_register_physical_memory(0x40000000, ram_size, ram_offset |
>>>>> IO_MEM_RAM);
>>>>> +
>>>>> +    /* Allocate BIOS */
>>>>> +    prom_size = 8 * 1024 * 1024; /* 8Mb */
>>>>> +    prom_offset = qemu_ram_alloc(NULL, "Leon3.bios", prom_size);
>>>>> +    cpu_register_physical_memory(0x00000000, prom_size,
>>>>> +                                 prom_offset | IO_MEM_ROM);
>>>>> +
>>>>> +    /* Load boot prom */
>>>>> +    if (bios_name == NULL)
>>>>> +        bios_name = PROM_FILENAME;
>>>>> +    filename = qemu_find_file(QEMU_FILE_TYPE_BIOS, bios_name);
>>>>> +
>>>>> +    bios_size = get_image_size(filename);
>>>>> +
>>>>> +    if (bios_size>    prom_size) {
>>>>> +        fprintf(stderr, "qemu: could not load prom '%s': file too big
>>>>> \n",
>>>>> +                filename);
>>>>> +        exit(1);
>>>>> +    }
>>>>> +
>>>>> +    if (bios_size>    0) {
>>>>> +        aligned_bios_size =
>>>>> +            (bios_size + TARGET_PAGE_SIZE - 1)&    TARGET_PAGE_MASK;
>>>>> +
>>>>> +        ret = load_image_targphys(filename, 0x00000000, bios_size);
>>>>> +        if (ret<    0 || ret>    prom_size) {
>>>>> +            fprintf(stderr, "qemu: could not load prom '%s'\n",
>>>>> filename);
>>>>> +            exit(1);
>>>>> +        }
>>>>> +    }
>>>>> +    else if (kernel_filename == NULL) {
>>>>> +        fprintf(stderr,"Can't read bios image %s\n", filename);
>>>>> +        exit(1);
>>>>> +    }
>>>>> +
>>>>> +    /* Can directly load an application. */
>>>>> +    if (kernel_filename != NULL) {
>>>>> +        long     kernel_size;
>>>>> +        uint64_t entry;
>>>>> +
>>>>> +        kernel_size = load_elf(kernel_filename, NULL, NULL,&entry,
>>>>> NULL,
>>>>> NULL,
>>>>> +                               1 /* big endian */, ELF_MACHINE, 0);
>>>>> +        if (kernel_size<    0) {
>>>>> +            fprintf(stderr, "qemu: could not load kernel '%s'\n",
>>>>> +                    kernel_filename);
>>>>> +            exit(1);
>>>>> +        }
>>>>> +        if (bios_size<= 0) {
>>>>> +            /* If there is no bios/monitor, start the application.  */
>>>>> +            env->pc = entry;
>>>>> +            env->npc = entry + 4;
>>>>> +            leon3_state.entry = entry;
>>>>> +        }
>>>>> +    }
>>>>> +
>>>>> +    /* Allocate timers */
>>>>> +    grlib_gptimer_create(0x80000300, 2, CPU_CLK, cpu_irqs, 6);
>>>>> +
>>>>> +    /* Allocate uart */
>>>>> +    if (serial_hds[0])
>>>>> +        grlib_apbuart_create(0x80000100, serial_hds[0], cpu_irqs[3]);
>>>>> +}
>>>>> +
>>>>> +QEMUMachine leon3_generic_machine = {
>>>>> +    .name     = "leon3_generic",
>>>>> +    .desc     = "Leon-3 generic",
>>>>> +    .init     = leon3_generic_hw_init,
>>>>> +    .use_scsi = 0,
>>>>> +};
>>>>> +
>>>>> +static void leon3_machine_init(void)
>>>>> +{
>>>>> +    qemu_register_machine(&leon3_generic_machine);
>>>>> +}
>>>>> +
>>>>> +machine_init(leon3_machine_init);
>>>>> diff --git a/target-sparc/cpu.h b/target-sparc/cpu.h
>>>>> index 7e0d17c..6020ffd 100644
>>>>> --- a/target-sparc/cpu.h
>>>>> +++ b/target-sparc/cpu.h
>>>>> @@ -474,6 +474,16 @@ void cpu_set_cwp(CPUState *env1, int new_cwp);
>>>>>  /* sun4m.c, sun4u.c */
>>>>>  void cpu_check_irqs(CPUSPARCState *env);
>>>>>
>>>>> +/* grlib_irqmp.c */
>>>>> +void grlib_irqmp_ack(CPUSPARCState *env, int intno);
>>>>> +
>>>>> +/* leon3.c */
>>>>> +void     leon3_shutdown(void);
>>>>> +void     leon3_cache_control_st(target_ulong addr, uint64_t val, int
>>>>> size);
>>>>> +uint64_t leon3_cache_control_ld(target_ulong addr, int size);
>>>>> +void     leon3_cache_control_int(void);
>>>>> +
>>>>> +
>>>>>  #if defined (TARGET_SPARC64)
>>>>>
>>>>>  static inline int compare_masked(uint64_t x, uint64_t y, uint64_t
>>>>> mask)
>>>>> diff --git a/target-sparc/helper.c b/target-sparc/helper.c
>>>>> index e84c312..3bf990f 100644
>>>>> --- a/target-sparc/helper.c
>>>>> +++ b/target-sparc/helper.c
>>>>> @@ -1295,7 +1295,7 @@ static const sparc_def_t sparc_defs[] = {
>>>>>         .iu_version = 0xf3000000,
>>>>>         .fpu_version = 4<<    17, /* FPU version 4 (Meiko) */
>>>>>         .mmu_version = 0xf3000000,
>>>>> -        .mmu_bm = 0x00004000,
>>>>> +        .mmu_bm = 0x00000000,
>>>>>         .mmu_ctpr_mask = 0x007ffff0,
>>>>>         .mmu_cxr_mask = 0x0000003f,
>>>>>         .mmu_sfsr_mask = 0xffffffff,
>>>>> diff --git a/target-sparc/op_helper.c b/target-sparc/op_helper.c
>>>>> index be3c1e0..85df077 100644
>>>>> --- a/target-sparc/op_helper.c
>>>>> +++ b/target-sparc/op_helper.c
>>>>> @@ -1609,8 +1609,13 @@ uint64_t helper_ld_asi(target_ulong addr, int
>>>>> asi,
>>>>> int size, int sign)
>>>>>
>>>>>     helper_check_align(addr, size - 1);
>>>>>     switch (asi) {
>>>>> -    case 2: /* SuperSparc MXCC registers */
>>>>> +    case 2: /* SuperSparc MXCC registers and Leon3 cache control */
>>>>>         switch (addr) {
>>>>> +        case 0x00:          /* Leon3 Cache Control */
>>>>> +        case 0x08:          /* Leon3 Instruction Cache config */
>>>>> +        case 0x0C:          /* Leon3 Date Cache config */
>>>>> +            ret = leon3_cache_control_ld(addr, size);
>>>>> +            break;
>>>>>         case 0x01c00a00: /* MXCC control register */
>>>>>             if (size == 8)
>>>>>                 ret = env->mxccregs[3];
>>>>> @@ -1838,8 +1843,14 @@ void helper_st_asi(target_ulong addr, uint64_t
>>>>> val, int asi, int size)
>>>>>  {
>>>>>     helper_check_align(addr, size - 1);
>>>>>     switch(asi) {
>>>>> -    case 2: /* SuperSparc MXCC registers */
>>>>> +    case 2: /* SuperSparc MXCC registers and Leon3 cache control */
>>>>>         switch (addr) {
>>>>> +        case 0x00:          /* Leon3 Cache Control */
>>>>> +        case 0x08:          /* Leon3 Instruction Cache config */
>>>>> +        case 0x0C:          /* Leon3 Date Cache config */
>>>>> +            leon3_cache_control_st(addr, val, size);
>>>>> +            break;
>>>>> +
>>>>>         case 0x01c00000: /* MXCC stream data register 0 */
>>>>>             if (size == 8)
>>>>>                 env->mxccdata[0] = val;
>>>>> @@ -4081,6 +4092,13 @@ void do_interrupt(CPUState *env)
>>>>>  {
>>>>>     int cwp, intno = env->exception_index;
>>>>>
>>>>> +#if !defined(CONFIG_USER_ONLY)
>>>>> +    /* Leon3 shutdown */
>>>>> +    if (intno == 0x80&&    env->version == 0xf3000000) {
>>>>> +        leon3_shutdown();
>>>>> +    }
>>>>
>>>> This looks like a hack. Should a trap instruction initiate a shutdown?
>>>
>>> Yes, on Leon3 "ta 0x0" initiates a shutdown.
>>
>> Then this should be handled during translation. A Leon3 specific CPU
>> feature should be added and used much like CHECK_IU_FEATURE (in
>> translate.c). Then execution speed would not be affected for non-Leon3
>> CPUs.
>>
>
> OK, but I don't see how to request a shutdown during translation.

Just create a helper which calls shutdown, translator should insert a
call to that.

>>>>> +#endif
>>>>> +
>>>>>  #ifdef DEBUG_PCALL
>>>>>     if (qemu_loglevel_mask(CPU_LOG_INT)) {
>>>>>         static int count;
>>>>> @@ -4135,6 +4153,14 @@ void do_interrupt(CPUState *env)
>>>>>     env->pc = env->tbr;
>>>>>     env->npc = env->pc + 4;
>>>>>     env->exception_index = -1;
>>>>> +
>>>>> +#if !defined(CONFIG_USER_ONLY)
>>>>> +    /* IRQ acknowledgment for Leon3 */
>>>>> +    if (env->version == 0xf3000000&&    (intno&    ~15) == TT_EXTINT)
>>>>> {
>>>>> +        grlib_irqmp_ack (env, intno);
>>>>> +        leon3_cache_control_int();
>>>>> +    }
>>>>
>>>> Like this. I don't think a CPU should immediately ack any incoming
>>>> interrupts.
>>>
>>> Leon3 does...
>>
>> Strange. Then this should be handled at board level (leon3.c).
>
> Well, it's a CPU feature not a board feature.

Maybe, but we don't want to clutter interrupt handling with this.