Re: [PATCH v3 10/18] target/s390: Return exception from mmu_translate

[David Hildenbrand]

On 26.09.19 18:26, Richard Henderson wrote:
> Do not raise the exception directly within mmu_translate,
> but pass it back so that caller may do so.
> 
> Signed-off-by: Richard Henderson <address@hidden>
> ---
>  target/s390x/internal.h    |  2 +-
>  target/s390x/excp_helper.c |  4 ++--
>  target/s390x/mem_helper.c  | 13 ++++++++++---
>  target/s390x/mmu_helper.c  | 36 ++++++++++++++----------------------
>  4 files changed, 27 insertions(+), 28 deletions(-)
> 
> diff --git a/target/s390x/internal.h b/target/s390x/internal.h
> index c4388aaf23..c993c3ef40 100644
> --- a/target/s390x/internal.h
> +++ b/target/s390x/internal.h
> @@ -360,7 +360,7 @@ void probe_write_access(CPUS390XState *env, uint64_t 
> addr, uint64_t len,
>  
>  /* mmu_helper.c */
>  int mmu_translate(CPUS390XState *env, target_ulong vaddr, int rw, uint64_t 
> asc,
> -                  target_ulong *raddr, int *flags, bool exc);
> +                  target_ulong *raddr, int *flags, uint64_t *tec);
>  int mmu_translate_real(CPUS390XState *env, target_ulong raddr, int rw,
>                         target_ulong *addr, int *flags, uint64_t *tec);
>  
> diff --git a/target/s390x/excp_helper.c b/target/s390x/excp_helper.c
> index 906b87c071..6a0728b65f 100644
> --- a/target/s390x/excp_helper.c
> +++ b/target/s390x/excp_helper.c
> @@ -140,8 +140,8 @@ bool s390_cpu_tlb_fill(CPUState *cs, vaddr address, int 
> size,
>          if (!(env->psw.mask & PSW_MASK_64)) {
>              vaddr &= 0x7fffffff;
>          }
> -        fail = mmu_translate(env, vaddr, access_type, asc, &raddr, &prot, 
> true);
> -        excp = 0; /* exception already raised */
> +        excp = mmu_translate(env, vaddr, access_type, asc, &raddr, &prot, 
> &tec);
> +        fail = excp;

... so what about instruction fetches? I assume this works as designed
as we set  env->int_pgm_ilen = 2 in s390_cpu_tlb_fill() in case of
MMU_INST_FETCH. But the comment indicates that "we may remove this
entirely".

Can you paint me the big picture? :)


>      } else if (mmu_idx == MMU_REAL_IDX) {
>          /* 31-Bit mode */
>          if (!(env->psw.mask & PSW_MASK_64)) {
> diff --git a/target/s390x/mem_helper.c b/target/s390x/mem_helper.c
> index 7d2a652823..e15aa296dd 100644
> --- a/target/s390x/mem_helper.c
> +++ b/target/s390x/mem_helper.c
> @@ -2364,8 +2364,8 @@ uint64_t HELPER(lra)(CPUS390XState *env, uint64_t addr)
>      CPUState *cs = env_cpu(env);
>      uint32_t cc = 0;
>      uint64_t asc = env->psw.mask & PSW_MASK_ASC;
> -    uint64_t ret;
> -    int old_exc, flags;
> +    uint64_t ret, tec;
> +    int old_exc, flags, exc;
>  
>      /* XXX incomplete - has more corner cases */
>      if (!(env->psw.mask & PSW_MASK_64) && (addr >> 32)) {
> @@ -2373,7 +2373,14 @@ uint64_t HELPER(lra)(CPUS390XState *env, uint64_t addr)
>      }
>  
>      old_exc = cs->exception_index;
> -    if (mmu_translate(env, addr, 0, asc, &ret, &flags, true)) {
> +    exc = mmu_translate(env, addr, 0, asc, &ret, &flags, &tec);
> +    if (exc) {
> +        /*
> +         * We don't care about ILEN or TEC, as we're not going to
> +         * deliver the exception -- thus resetting exception_index below.
> +         * TODO: clean this up.
> +         */
> +        trigger_pgm_exception(env, exc, ILEN_UNWIND);

Yeah, this needs a cleanup.

>          cc = 3;
>      }
>      if (cs->exception_index == EXCP_PGM) {
> diff --git a/target/s390x/mmu_helper.c b/target/s390x/mmu_helper.c
> index ed6570db62..a9219942b1 100644
> --- a/target/s390x/mmu_helper.c
> +++ b/target/s390x/mmu_helper.c
> @@ -349,17 +349,15 @@ static void mmu_handle_skey(target_ulong addr, int rw, 
> int *flags)
>   * @return       0 if the translation was successful, -1 if a fault occurred
>   */
>  int mmu_translate(CPUS390XState *env, target_ulong vaddr, int rw, uint64_t 
> asc,
> -                  target_ulong *raddr, int *flags, bool exc)
> +                  target_ulong *raddr, int *flags, uint64_t *tec)
>  {
> -    /* Code accesses have an undefined ilc, let's use 2 bytes. */
> -    const int ilen = (rw == MMU_INST_FETCH) ? 2 : ILEN_AUTO;

Now I realize that this ilen currently gets overwritten in
s390_cpu_tlb_fill().

> -    uint64_t tec = (vaddr & TARGET_PAGE_MASK) | (asc >> 46) |
> -                   (rw == MMU_DATA_STORE ? FS_WRITE : FS_READ);
>      uint64_t asce;
>      int r;
>  
> -
> +    *tec = (vaddr & TARGET_PAGE_MASK) | (asc >> 46) |
> +            (rw == MMU_DATA_STORE ? FS_WRITE : FS_READ);
>      *flags = PAGE_READ | PAGE_WRITE | PAGE_EXEC;
> +
>      if (is_low_address(vaddr & TARGET_PAGE_MASK) && lowprot_enabled(env, 
> asc)) {
>          /*
>           * If any part of this page is currently protected, make sure the
> @@ -371,10 +369,7 @@ int mmu_translate(CPUS390XState *env, target_ulong 
> vaddr, int rw, uint64_t asc,
>           */
>          *flags |= PAGE_WRITE_INV;
>          if (is_low_address(vaddr) && rw == MMU_DATA_STORE) {
> -            if (exc) {
> -                trigger_access_exception(env, PGM_PROTECTION, ILEN_AUTO, 0);
> -            }
> -            return -EACCES;
> +            return PGM_PROTECTION;
>          }
>      }
>  
> @@ -404,20 +399,14 @@ int mmu_translate(CPUS390XState *env, target_ulong 
> vaddr, int rw, uint64_t asc,
>      /* perform the DAT translation */
>      r = mmu_translate_asce(env, vaddr, asc, asce, raddr, flags, rw);
>      if (unlikely(r)) {
> -        if (exc) {
> -            trigger_access_exception(env, r, ilen, tec);
> -        }
> -        return -1;
> +        return r;
>      }
>  
>      /* check for DAT protection */
>      if (unlikely(rw == MMU_DATA_STORE && !(*flags & PAGE_WRITE))) {
> -        if (exc) {
> -            /* DAT sets bit 61 only */
> -            tec |= 0x4;
> -            trigger_access_exception(env, PGM_PROTECTION, ilen, tec);
> -        }
> -        return -1;
> +        /* DAT sets bit 61 only */
> +        *tec |= 0x4;
> +        return PGM_PROTECTION;
>      }
>  
>  nodat:
> @@ -441,9 +430,12 @@ static int translate_pages(S390CPU *cpu, vaddr addr, int 
> nr_pages,
>      int ret, i, pflags;
>  
>      for (i = 0; i < nr_pages; i++) {
> -        ret = mmu_translate(env, addr, is_write, asc, &pages[i], &pflags, 
> true);
> +        uint64_t tec;
> +
> +        ret = mmu_translate(env, addr, is_write, asc, &pages[i], &pflags, 
> &tec);
>          if (ret) {
> -            return ret;
> +            trigger_access_exception(env, ret, ILEN_AUTO, tec);
> +            return -EFAULT;
>          }
>          if (!address_space_access_valid(&address_space_memory, pages[i],
>                                          TARGET_PAGE_SIZE, is_write,
> 


-- 

Thanks,

David / dhildenb