Re: [Qemu-devel] [PATCH] s390x/tcg: fixup TEST PROTECTION

[Cornelia Huck <cohuck@redhat.com>]

On Wed, 17 Jan 2018 16:37:37 +0100
David Hildenbrand <david@redhat.com> wrote:

> On 12.01.2018 13:54, David Hildenbrand wrote:
> > CC == 2 can only happen due to a protection exception, not if memory is
> > not available (PGM_ADDRESSING). So all PGM_ADDRESSING exceptions have to
> > be forwarded to the guest.
> > 
> > Since the initial definition of TEST PROTECTION, we now read globals
> > (e.g. PSW mask), so we have to correctly mark the instruction
> > (otherwise, e.g. booting fedora 27 fails).
> > 
> > Also, the architecture explicitly specifies which exceptions are
> > forwarded to the guest, this makes the code a little nicer.
> > 
> > Signed-off-by: David Hildenbrand <david@redhat.com>
> > ---
> >  target/s390x/cpu.h        |  2 ++
> >  target/s390x/helper.h     |  2 +-
> >  target/s390x/EM_helper.c | 41 +++++++++++++++++++----------------------
> >  3 files changed, 22 insertions(+), 23 deletions(-)
> > 
> > diff --git a/target/s390x/cpu.h b/target/s390x/cpu.h
> > index 1a8b6b9ae9..915bccbc75 100644
> > --- a/target/s390x/cpu.h
> > +++ b/target/s390x/cpu.h
> > @@ -759,6 +759,8 @@ int s390_cpu_virt_mem_rw(S390CPU *cpu, vaddr laddr, uint8_t ar, void *hostbuf,
> >          s390_cpu_virt_mem_rw(cpu, laddr, ar, dest, len, false)
> >  #define s390_cpu_virt_mem_write(cpu, laddr, ar, dest, len)       \
> >          s390_cpu_virt_mem_rw(cpu, laddr, ar, dest, len, true)
> > +#define s390_cpu_virt_mem_check_read(cpu, laddr, ar, len)   \
> > +        s390_cpu_virt_mem_rw(cpu, laddr, ar, NULL, len, false)
> >  #define s390_cpu_virt_mem_check_write(cpu, laddr, ar, len)   \
> >          s390_cpu_virt_mem_rw(cpu, laddr, ar, NULL, len, true)
> >  void s390_cpu_virt_mem_handle_exc(S390CPU *cpu, uintptr_t ra);
> > diff --git a/target/s390x/helper.h b/target/s390x/helper.h
> > index 26c1b07b44..59a1d9869b 100644
> > --- a/target/s390x/helper.h
> > +++ b/target/s390x/helper.h
> > @@ -137,7 +137,7 @@ DEF_HELPER_FLAGS_4(lctlg, TCG_CALL_NO_WG, void, env, i32, i64, i32)
> >  DEF_HELPER_FLAGS_4(stctl, TCG_CALL_NO_WG, void, env, i32, i64, i32)
> >  DEF_HELPER_FLAGS_4(stctg, TCG_CALL_NO_WG, void, env, i32, i64, i32)
> >  DEF_HELPER_FLAGS_2(testblock, TCG_CALL_NO_WG, i32, env, i64)
> > -DEF_HELPER_FLAGS_3(tprot, TCG_CALL_NO_RWG, i32, env, i64, i64)
> > +DEF_HELPER_FLAGS_3(tprot, TCG_CALL_NO_WG, i32, env, i64, i64)
> >  DEF_HELPER_FLAGS_2(iske, TCG_CALL_NO_RWG_SE, i64, env, i64)
> >  DEF_HELPER_FLAGS_3(sske, TCG_CALL_NO_RWG, void, env, i64, i64)
> >  DEF_HELPER_FLAGS_2(rrbe, TCG_CALL_NO_RWG, i32, env, i64)
> > diff --git a/target/s390x/mem_helper.c b/target/s390x/mem_helper.c
> > index 359e446c6f..c957febc6d 100644
> > --- a/target/s390x/mem_helper.c
> > +++ b/target/s390x/mem_helper.c
> > @@ -1730,34 +1730,31 @@ uint32_t HELPER(tprot)(CPUS390XState *env, uint64_t a1, uint64_t a2)
> >          /* Fetching permitted; storing permitted */
> >          return 0;
> >      }
> > +
> > +    if (env->int_pgm_code == PGM_PROTECTION) {
> > +        /* retry if reading is possible */
> > +        cs->exception_index = 0;
> > +        if (!s390_cpu_virt_mem_check_read(cpu, a1, 0, 1)) {
> > +            /* Fetching permitted; storing not permitted */
> > +            return 1;
> > +        }
> > +    }
> > +
> >      switch (env->int_pgm_code) {
> >      case PGM_PROTECTION:
> > -        /* Fetching permitted; storing not permitted */
> > -        cs->exception_index = 0;
> > -        return 1;
> > -    case PGM_ADDRESSING:
> >          /* Fetching not permitted; storing not permitted */
> >          cs->exception_index = 0;
> >          return 2;
> > -    case PGM_ASCE_TYPE:
> > -    case PGM_REG_FIRST_TRANS:
> > -    case PGM_REG_SEC_TRANS:
> > -    case PGM_REG_THIRD_TRANS:
> > -    case PGM_SEGMENT_TRANS:
> > -    case PGM_PAGE_TRANS:
> > -    case PGM_ALET_SPEC:
> > -    case PGM_ALEN_SPEC:
> > -    case PGM_ALE_SEQ:
> > -    case PGM_ASTE_VALID:
> > -    case PGM_ASTE_SEQ:
> > -    case PGM_EXT_AUTH:
> > -        /* Translation not available */
> > -        cs->exception_index = 0;
> > -        return 3;
> > +    case PGM_ADDRESSING:
> > +    case PGM_TRANS_SPEC:
> > +        /* exceptions forwarded to the guest */
> > +        s390_cpu_virt_mem_handle_exc(cpu, GETPC());
> > +        return 0;
> >      }
> > -    /* any other exception is forwarded to the guest */
> > -    s390_cpu_virt_mem_handle_exc(cpu, GETPC());
> > -    return 0;
> > +
> > +    /* Translation not available */
> > +    cs->exception_index = 0;
> > +    return 3;
> >  }
> >  
> >  /* insert storage key extended */
> >   
> 
> Ping, this is certainly better than the current (queued) state. Would
> love to see some review. But if nobody volunteers to read the PoP, I
> think my current use case (Linux and kvm-unit-tests) have to be
> sufficient for now.

I'm a bit low on review cycles, unfortunately.

I guess I will just queue this for the next batch if nobody speaks up
to the contrary.