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Date: Mon, 12 Jan 2009 23:03:48 +0100
From: Jakub Jermar <jakub@jermar.eu>
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Subject: [Qemu-devel] Re: sparc64's get_physical_address_code should not
 fault on TTE's with V=0
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To: Blue Swirl <blauwirbel@gmail.com>
Cc: openbios@openbios.org, qemu-devel@nongnu.org

Blue Swirl wrote:
> On 1/12/09, Jakub Jermar <jakub@jermar.eu> wrote:
>> Hi,
>>
>>  when I make the following change to helper.c, get_physical_address_code:
>>
>>  -        // ctx match, vaddr match?
>>  +        // ctx match, vaddr match, valid?
>>          if (env->dmmuregs[1] == (env->itlb_tag[i] & 0x1fff) &&
>>  -            (address & mask) == (env->itlb_tag[i] & ~0x1fffULL)) {
>>  -            // valid, access ok?
>>  -            if ((env->itlb_tte[i] & 0x8000000000000000ULL) == 0 ||
>>  -                ((env->itlb_tte[i] & 0x4) && is_user)) {
>>  +            (address & mask) == (env->itlb_tag[i] & ~0x1fffULL) &&
>>  +            env->itlb_tte[i] & 0x8000000000000000ULL) {
>>  +            // access ok?
>>  +            if ((env->itlb_tte[i] & 0x4) && is_user) {
>>
>>  HelenOS gets a little bit further than without this change and seems
>>  to panic more or less gracefully later.
>>
>>  In short, non-valid entries should be skipped by the loop in
>>  get_physical_address_code instead of causing TFAULT, because
>>  the ITLB can contain a valid entry for the same address. The
>>  same is true for DTLB.
>>
>>  Can you confirm this?
> 
> Yes, this looks correct. I'll apply a fix.

Thanks!

With this fix in place, HelenOS most of the time panics on:

Kernel panic: Cannot find property 'screen'.

I.e. it searches property 'screen' in /aliases and doesn't
find any. If it is not there already, could you please add
it (together with keyboard) to openbios?

Thanks,
Jakub