Re: [Qemu-arm] [PATCH] hw/intc/armv7m: Support byte and halfword accesses to CFSR

[Philippe Mathieu-Daudé]

Hi Peter,

On 12/08/2017 11:12 AM, Peter Maydell wrote:
> The Configurable Fault Status Register for ARMv7M and v8M is
> supposed to be byte and halfword accessible, but we were only

"aligned halfword"

> implementing word accesses. Add support for the other access
> sizes, which are used by the Zephyr RTOS.
> 
> Signed-off-by: Peter Maydell <address@hidden>
> Reported-by: Andy Gross <address@hidden>
> ---
>  hw/intc/armv7m_nvic.c | 38 ++++++++++++++++++++++----------------
>  1 file changed, 22 insertions(+), 16 deletions(-)
> 
> diff --git a/hw/intc/armv7m_nvic.c b/hw/intc/armv7m_nvic.c
> index 5d9c883..dc8e2f1 100644
> --- a/hw/intc/armv7m_nvic.c
> +++ b/hw/intc/armv7m_nvic.c
> @@ -896,13 +896,6 @@ static uint32_t nvic_readl(NVICState *s, uint32_t 
> offset, MemTxAttrs attrs)
>              val |= (1 << 8);
>          }
>          return val;
> -    case 0xd28: /* Configurable Fault Status.  */
> -        /* The BFSR bits [15:8] are shared between security states
> -         * and we store them in the NS copy
> -         */
> -        val = cpu->env.v7m.cfsr[attrs.secure];
> -        val |= cpu->env.v7m.cfsr[M_REG_NS] & R_V7M_CFSR_BFSR_MASK;
> -        return val;
>      case 0xd2c: /* Hard Fault Status.  */
>          return cpu->env.v7m.hfsr;
>      case 0xd30: /* Debug Fault Status.  */
> @@ -1280,15 +1273,6 @@ static void nvic_writel(NVICState *s, uint32_t offset, 
> uint32_t value,
>          s->vectors[ARMV7M_EXCP_DEBUG].active = (value & (1 << 8)) != 0;
>          nvic_irq_update(s);
>          break;
> -    case 0xd28: /* Configurable Fault Status.  */
> -        cpu->env.v7m.cfsr[attrs.secure] &= ~value; /* W1C */
> -        if (attrs.secure) {
> -            /* The BFSR bits [15:8] are shared between security states
> -             * and we store them in the NS copy.
> -             */
> -            cpu->env.v7m.cfsr[M_REG_NS] &= ~(value & R_V7M_CFSR_BFSR_MASK);
> -        }
> -        break;
>      case 0xd2c: /* Hard Fault Status.  */
>          cpu->env.v7m.hfsr &= ~value; /* W1C */
>          break;
> @@ -1667,6 +1651,14 @@ static MemTxResult nvic_sysreg_read(void *opaque, 
> hwaddr addr,
>              val = deposit32(val, i * 8, 8, get_prio(s, hdlidx, sbank));
>          }
>          break;
> +    case 0xd28 ... 0xd2b: /* Configurable Fault Status (CFSR) */
> +        /* The BFSR bits [15:8] are shared between security states
> +         * and we store them in the NS copy
> +         */
> +        val = s->cpu->env.v7m.cfsr[attrs.secure];
> +        val |= s->cpu->env.v7m.cfsr[M_REG_NS] & R_V7M_CFSR_BFSR_MASK;
> +        val = extract32(val, (offset - 0xd28) * 8, size * 8);
> +        break;

we have:

static const MemoryRegionOps nvic_sysreg_ops = {
    .read_with_attrs = nvic_sysreg_read,
    .write_with_attrs = nvic_sysreg_write,
    .endianness = DEVICE_NATIVE_ENDIAN,
};

with:
    /* If true, unaligned accesses are supported.  Otherwise unaligned
     * accesses throw machine checks.
     */
    bool unaligned;

So unaligned halfword should throw excp.

We could add an explicit ".unaligned = false,"

>      case 0xfe0 ... 0xfff: /* ID.  */
>          if (offset & 3) {
>              val = 0;
> @@ -1765,6 +1757,20 @@ static MemTxResult nvic_sysreg_write(void *opaque, 
> hwaddr addr,
>          }
>          nvic_irq_update(s);
>          return MEMTX_OK;
> +    case 0xd28 ... 0xd2b: /* Configurable Fault Status (CFSR) */
> +        /* All bits are W1C, so construct 32 bit value with 0s in
> +         * the parts not written by the access size
> +         */

This comment is welcomed :)

> +        value <<= ((offset - 0xd28) * 8);
> +
> +        s->cpu->env.v7m.cfsr[attrs.secure] &= ~value;
> +        if (attrs.secure) {
> +            /* The BFSR bits [15:8] are shared between security states
> +             * and we store them in the NS copy.
> +             */
> +            s->cpu->env.v7m.cfsr[M_REG_NS] &= ~(value & 
> R_V7M_CFSR_BFSR_MASK);
> +        }
> +        return MEMTX_OK;
>      }
>      if (size == 4) {
>          nvic_writel(s, offset, value, attrs);

Reviewed-by: Philippe Mathieu-Daudé <address@hidden>

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