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Re: [Qemu-devel] qemu hw/ppc_oldworld.c target-ppc/cpu.h target-...
From: |
Fabrice Bellard |
Subject: |
Re: [Qemu-devel] qemu hw/ppc_oldworld.c target-ppc/cpu.h target-... |
Date: |
Sat, 24 Nov 2007 20:39:06 +0100 |
User-agent: |
Thunderbird 1.5.0.9 (X11/20070212) |
Thiemo Seufer wrote:
> Paul Brook wrote:
>>>> I think what you mean is that they work the way that ppc64 is defined, to
>>>> remain compatible with ppc32. IMHO this is entirely irrelevant as we're
>>>> emulating a ppc32. You could replace the high bits with garbage and
>>>> nothing would ever be able to tell the difference.
>>> PowerPC is a 64 bits architecture. PowerPC 32 on 32 bits host is
>>> optimized not to compute the 32 highest bits, the same way it's allowed
>>> to cut down the GPR when implementing a CPU that would not support the
>>> 64 bits mode (but this is a tolerance, this is not the architecture is
>>> defined).
>> No. PowerPC is defined as a 64-bit archirecure. However there is a subset of
>> this architecture (aka ppc32) that is a complete 32-bit architecture in its
>> own right. By your own admission, we can get away with not calculating the
>> high 32 bit of the register. If follows that the high bits are completely
>> meaningless.
>
> This btw. also means that the ppc32 emulation on 32-bit hosts is needlessly
> inefficient if the high bits are carried around.
>
>> The qemu ppc32 emulation is implemented in such a way that on 64-bit hosts
>> it
>> looks a lot like a ppc64 implementation. However this need not, and should
>> not be exposed to the user.
>>
>>> OK. Those are real bugs to be fixed. I'll take a look.... But I'll try
>>> not to break the GPR dump. In fact, GPR should always dumped as 64 bits,
>>> even when runnig on 32 bits hosts. This would be more consistent with
>>> the specification.
>> I disagree. qemu is implementing ppc32. Showing more than 32 bits of
>> register
>> is completely bogus. Any differences between a 32-bit host and a 64-bit host
>> are a qemu bug. If you display 64 bits, then those 64 bits had better be the
>> same when run on 32-bit hosts.
>
> I strongly agree with Paul.
I strongly agree too and I suggest to remove the type ppc_gpr_t and to
replace it with target_ulong (and uint32_t for the high part of the SPE
extensions).
Regards,
Fabrice.
- Re: [Qemu-devel] qemu hw/ppc_oldworld.c target-ppc/cpu.h target-..., (continued)
- Re: [Qemu-devel] qemu hw/ppc_oldworld.c target-ppc/cpu.h target-..., Paul Brook, 2007/11/23
- Re: [Qemu-devel] qemu hw/ppc_oldworld.c target-ppc/cpu.h target-..., Jocelyn Mayer, 2007/11/23
- Re: [Qemu-devel] qemu hw/ppc_oldworld.c target-ppc/cpu.h target-..., Jocelyn Mayer, 2007/11/23
- Re: [Qemu-devel] qemu hw/ppc_oldworld.c target-ppc/cpu.h target-..., Paul Brook, 2007/11/23
- Re: [Qemu-devel] qemu hw/ppc_oldworld.c target-ppc/cpu.h target-..., Jocelyn Mayer, 2007/11/23
- Re: [Qemu-devel] qemu hw/ppc_oldworld.c target-ppc/cpu.h target-..., Jocelyn Mayer, 2007/11/23
- Re: [Qemu-devel] qemu hw/ppc_oldworld.c target-ppc/cpu.h target-..., Paul Brook, 2007/11/23
- Re: [Qemu-devel] qemu hw/ppc_oldworld.c target-ppc/cpu.h target-..., J. Mayer, 2007/11/23
- Re: [Qemu-devel] qemu hw/ppc_oldworld.c target-ppc/cpu.h target-..., Paul Brook, 2007/11/23
- Re: [Qemu-devel] qemu hw/ppc_oldworld.c target-ppc/cpu.h target-..., Thiemo Seufer, 2007/11/23
- Re: [Qemu-devel] qemu hw/ppc_oldworld.c target-ppc/cpu.h target-...,
Fabrice Bellard <=
- Re: [Qemu-devel] qemu hw/ppc_oldworld.c target-ppc/cpu.h target-..., J. Mayer, 2007/11/23
- Re: [Qemu-devel] qemu hw/ppc_oldworld.c target-ppc/cpu.h target-..., Thiemo Seufer, 2007/11/23
- Re: [Qemu-devel] qemu hw/ppc_oldworld.c target-ppc/cpu.h target-..., Paul Brook, 2007/11/23
- Re: [Qemu-devel] qemu hw/ppc_oldworld.c target-ppc/cpu.h target-..., Julian Seward, 2007/11/23
- Re: [Qemu-devel] qemu hw/ppc_oldworld.c target-ppc/cpu.h target-..., J. Mayer, 2007/11/23
- Re: [Qemu-devel] qemu hw/ppc_oldworld.c target-ppc/cpu.h target-..., J. Mayer, 2007/11/23
[Qemu-devel] qemu hw/ppc_oldworld.c target-ppc/cpu.h target-..., Jocelyn Mayer, 2007/11/23