Re: [Qemu-devel] [PATCH-for-4.2 v1 1/9] s390x/mmu: Better ASC selection in s390_cpu_get_phys_page_debug()

[Thomas Huth <thuth@redhat.com>]

On 8/5/19 5:29 PM, David Hildenbrand wrote:
> Let's select the ASC before calling the function and use MMU_DATA_LOAD.
> This is a preparation to:
> - Remove the ASC magic depending on the access mode from mmu_translate
> - Implement IEP support, where we could run into access exceptions
>   trying to fetch instructions
> 
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  target/s390x/helper.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/target/s390x/helper.c b/target/s390x/helper.c
> index 13ae9909ad..08166558a0 100644
> --- a/target/s390x/helper.c
> +++ b/target/s390x/helper.c
> @@ -58,7 +58,15 @@ hwaddr s390_cpu_get_phys_page_debug(CPUState *cs, vaddr vaddr)
>          vaddr &= 0x7fffffff;
>      }
>  
> -    if (mmu_translate(env, vaddr, MMU_INST_FETCH, asc, &raddr, &prot, false)) {
> +    /*
> +     * We want to read the code, however, not run into access exceptions

Is this really a safe assumption here that we always use this to
translate code addresses and not data addresses? ... I don't think so.
For example with the "gva2gpa" HMP command, I'd rather expect that it
also works with the secondary space mode...?

So maybe we need a proper MemTxAttrs bit or something similar for
distinguishing instruction accesses from data accesses here?

 Thomas