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Date: Mon, 23 Jan 2012 18:33:51 +0100
From: Alexander Graf <agraf@suse.de>
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Subject: Re: [Qemu-devel] [PATCH 7/8] PPC: booke206: Check for min/max TLB
	entry size
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To: Scott Wood <scottwood@freescale.com>
Cc: qemu-ppc@nongnu.org, qemu-devel Developers <qemu-devel@nongnu.org>

On 01/23/2012 06:32 PM, Scott Wood wrote:
> On 01/20/2012 10:15 PM, Alexander Graf wrote:
>> @@ -4273,6 +4274,16 @@ void helper_booke206_tlbwe(void)
>>           tlb->mas1&= ~MAS1_IPROT;
>>       }
>>
>> +    /* check that we support the targeted size */
>> +    size_tlb = (tlb->mas1&  MAS1_TSIZE_MASK)>>  MAS1_TSIZE_SHIFT;
>> +    size_ps = booke206_tlbnps(env, tlbn);
>> +    if ((tlb->mas1&  MAS1_VALID)&&  (tlbncfg&  TLBnCFG_AVAIL)&&
>> +        !(size_ps&  (1<<  size_tlb))) {
>> +        helper_raise_exception_err(POWERPC_EXCP_PROGRAM,
>> +                                   POWERPC_EXCP_INVAL |
>> +                                   POWERPC_EXCP_INVAL_INVAL);
>> +    }
>> +
>>       if (booke206_tlb_to_page_size(env, tlb) == TARGET_PAGE_SIZE) {
>>           tlb_flush_page(env, tlb->mas2&  MAS2_EPN_MASK);
>>       } else {
> For tlb0 on e500 and derivatives, tsize is explicitly documented as
> ignored.  Software may rely on this.

Yup, that's why there's the check for TLBnCG_AVAIL, which indicates that 
a TLB has dynamic page size capabilities, which TLB0 does not have.


Alex