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Re: [Qemu-devel] Minor MMU fixes for PowerPC 40x emulation
From: |
Alexander Graf |
Subject: |
Re: [Qemu-devel] Minor MMU fixes for PowerPC 40x emulation |
Date: |
Sat, 2 Oct 2010 19:10:03 +0200 |
On 02.10.2010, at 19:06, Edgar E. Iglesias wrote:
> On Sat, Oct 02, 2010 at 06:55:36PM +0200, Alexander Graf wrote:
>>
>> On 02.10.2010, at 18:49, John Clark wrote:
>>
>>>>> /* Check from TLB entry */
>>>>> - /* XXX: there is a problem here or in the TLB fill code... */
>>>>> + /* There is no longer a need to force PAGE_EXEC permission
>>>>> here */
>>>>> + /* because of the tlb->attr fix in helper_4xx_tlbwe_lo() */
>>>>
>>>> I guess that comment is superfluous, as readers several years from now
>>>> don't care what was broken back in the day :).
>>>
>>> Yes, I suppose so :)
>>>
>>>>> @@ -3939,7 +3939,7 @@ target_ulong helper_4xx_tlbre_lo (target_ulong
>>>>> entry)
>>>>> tlb = &env->tlb[entry].tlbe;
>>>>> ret = tlb->EPN;
>>>>> if (tlb->prot & PAGE_VALID)
>>>>> - ret |= 0x400;
>>>>> + ret |= 0x40; /* V bit is 0x40, not 0x400 */
>>>>
>>>> Ouch. Mind to make it a define?
>>>
>>> Sure, I was surprised that there wasn't a define for that when I found it.
>>
>> The ppc emulation code lacks a lot of defines. In fact, the same goes for
>> x86 emulation too ;). But that doesn't mean we have to keep it that way!
>>
>>>
>>>>> size = booke_page_size_to_tlb(tlb->size);
>>>>> if (size < 0 || size > 0x7)
>>>>> size = 1;
>>>>> @@ -3948,7 +3948,7 @@ target_ulong helper_4xx_tlbre_lo (target_ulong
>>>>> entry)
>>>>> return ret;
>>>>> }
>>>>>
>>>>> -target_ulong helper_4xx_tlbre_hi (target_ulong entry)
>>>>> +target_ulong helper_4xx_tlbre_lo (target_ulong entry)
>>>>
>>>> Huh?
>>>
>>> To summarize, 'tlbre' has two forms: one to retrieve the high bits of
>>> a TLB entry (TLBHI), and one to retrieve the low bits (TLBLO) of a TLB
>>> entry. This code had the TLBLO form returning the bits corresponding
>>> to TLBHI and vice versa, hence the name change. You can verify this
>>> if you like with this IBM PowerPC 405 core user manual on page 362:
>>
>> Well the thing that strikes me as weird is mostly that you're changing a
>> function name, but no callers to it. So is this function never used? Or was
>> tlbre_lo defined before already and is now defined twice?
>
> Hi,
>
> Alex:
> I think you've missed the part of the patch that renames the _lo -> _hi.
> As John says, qemu had the hi/lo parts reversed when reading 4xx TLB regs.
Oh. THERE it is! Hah. Yeah, I really missed that line - exchanging both
functions makes sense.
Thanks,
Alex
- [Qemu-devel] Minor MMU fixes for PowerPC 40x emulation, John Clark, 2010/10/02
- Re: [Qemu-devel] Minor MMU fixes for PowerPC 40x emulation, Alexander Graf, 2010/10/02
- Message not available
- Re: [Qemu-devel] Minor MMU fixes for PowerPC 40x emulation, Alexander Graf, 2010/10/02
- Re: [Qemu-devel] Minor MMU fixes for PowerPC 40x emulation, John Clark, 2010/10/02
- Re: [Qemu-devel] Minor MMU fixes for PowerPC 40x emulation, Edgar E. Iglesias, 2010/10/02
- Re: [Qemu-devel] Minor MMU fixes for PowerPC 40x emulation,
Alexander Graf <=
- Re: [Qemu-devel] Minor MMU fixes for PowerPC 40x emulation, John Clark, 2010/10/02
- Re: [Qemu-devel] Minor MMU fixes for PowerPC 40x emulation, Alexander Graf, 2010/10/05
- Re: [Qemu-devel] Minor MMU fixes for PowerPC 40x emulation, Edgar E. Iglesias, 2010/10/05