Re: [Qemu-devel] [PATCH 06/11] Add support for S390x system emulation

[Aurelien Jarno]

On Wed, Dec 02, 2009 at 09:27:21AM +0100, Alexander Graf wrote:
> 
> On 02.12.2009, at 09:09, Aurelien Jarno wrote:
> 
> > On Mon, Nov 30, 2009 at 11:19:06PM +0100, Alexander Graf wrote:
> >> 
> >> On 30.11.2009, at 19:18, Aurelien Jarno wrote:
> >> 
> >>> On Thu, Nov 26, 2009 at 02:23:15PM +0100, Alexander Graf wrote:
> >>>> Let's enable the basics for system emulation so we can run virtual 
> >>>> machines
> >>>> with KVM!
> >>> 
> >>> I don't really understand while this whole patch is not merged in patch
> >>> number 1. Otherwise, please find the comments below.
> >> 
> >> Historical reasons. To keep Uli's stripped down version separate from my 
> >> code.
> >> 
> >>> 
> >>>> Signed-off-by: Alexander Graf <address@hidden>
> >>>> ---
> >>>> target-s390x/cpu.h                |  153 
> >>>> ++++++++++++++++++++++++++++++++++++-
> >>>> target-s390x/exec.h               |    5 +
> >>>> target-s390x/helper.c             |   22 +++++
> >>>> target-s390x/machine.c            |   30 +++++++
> >>>> 4 files changed, 208 insertions(+), 2 deletions(-)
> >>>> create mode 100644 default-configs/s390x-softmmu.mak
> >>>> create mode 100644 target-s390x/machine.c
> >>>> 
> >>>> diff --git a/default-configs/s390x-softmmu.mak 
> >>>> b/default-configs/s390x-softmmu.mak
> >>>> new file mode 100644
> >>>> index 0000000..e69de29
> >>>> diff --git a/target-s390x/cpu.h b/target-s390x/cpu.h
> >>>> index f45b00c..a74745c 100644
> >>>> --- a/target-s390x/cpu.h
> >>>> +++ b/target-s390x/cpu.h
> >>>> @@ -30,8 +30,7 @@
> >>>> 
> >>>> #include "softfloat.h"
> >>>> 
> >>>> -#define NB_MMU_MODES 2 // guess
> >>>> -#define MMU_USER_IDX 0 // guess
> >>>> +#define NB_MMU_MODES 2
> >>>> 
> >>>> typedef union FPReg {
> >>>>    struct {
> >>>> @@ -77,6 +76,15 @@ static inline void cpu_clone_regs(CPUState *env, 
> >>>> target_ulong newsp)
> >>>> }
> >>>> #endif
> >>>> 
> >>>> +#define MMU_MODE0_SUFFIX _kernel
> >>>> +#define MMU_MODE1_SUFFIX _user
> >>>> +#define MMU_USER_IDX 1
> >>>> +static inline int cpu_mmu_index (CPUState *env)
> >>>> +{
> >>>> +    /* XXX: Currently we don't implement virtual memory */
> >>>> +    return 0;
> >>> 
> >>> Is it correct? It means that memory access will aways be kernel memory
> >>> accesses. IIRC, even with KVM enabled, softmmu accesses are possible in
> >>> some cases (devices ?).
> >> 
> >> I can't imagine any hardware using the CPU's MMU to write to RAM. That's 
> >> what IOMMUs are for.
> >> 
> >> The only 2 consumers are:
> >> 
> >> 1) tcg
> >> 2) gdb / monitor
> >> 
> >> With 2) being broken, because we can't resolve virtual addresses to 
> >> physical addresses. But that won't change until someone implements the 
> >> softmmu emulation target for real.
> > 
> > If it is sure it is never used, I would prefer to see an abort().
> > Otherwise it's fine.
> 
> I don't think I understand where you want to put the abort().
> 

In inline cpu_mmu_index(), just before the return, to make sure this
function is never called, as it is clearly wrong.

-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
address@hidden                 http://www.aurel32.net