Re: [PATCH] hvf: Handle EC_INSNABORT

[Peter Maydell]

On Thu, 1 Jun 2023 at 15:33, Antonio Caggiano <quic_acaggian@quicinc.com> wrote:
>
> Instead of aborting immediately, try reading the physical address where
> the instruction should be fetched by calling address_space_read. This
> would give any memory regions ops callback a chance to allocate and/or
> register an RAM/Alias memory region needed for resolving that physical
> address. Then, if the memory transaction is OK, retry HVF execution at
> the same PC.

What are the circumstances where this happens?
Do we try to support this on KVM ?


> Signed-off-by: Antonio Caggiano <quic_acaggian@quicinc.com>
> Co-authored-by: Mark Burton <quic_mburton@quicinc.com>
> ---
>  target/arm/hvf/hvf.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/target/arm/hvf/hvf.c b/target/arm/hvf/hvf.c
> index ad65603445..6e527254b1 100644
> --- a/target/arm/hvf/hvf.c
> +++ b/target/arm/hvf/hvf.c
> @@ -1446,6 +1446,18 @@ int hvf_vcpu_exec(CPUState *cpu)
>              hvf_raise_exception(cpu, EXCP_UDEF, syn_uncategorized());
>          }
>          break;
> +    case EC_INSNABORT: {
> +        uint32_t sas = (syndrome >> 22) & 3;
> +        uint32_t len = 1 << sas;
> +        uint64_t val = 0;
> +
> +        MemTxResult res = address_space_read(
> +            &address_space_memory, hvf_exit->exception.physical_address,
> +            MEMTXATTRS_UNSPECIFIED, &val, len);
> +        assert(res == MEMTX_OK);

You can't assert() this, it might not be true, especially if
we're here because hvf couldn't read from this address.

> +        flush_cpu_state(cpu);
> +        break;
> +    }
>      default:
>          cpu_synchronize_state(cpu);
>          trace_hvf_exit(syndrome, ec, env->pc);

thanks
-- PMM