Re: [Qemu-devel] [PATCH for-2.0?] target-i386: fix gdb debugging with large memory guests

[Paolo Bonzini <pbonzini@redhat.com>]

Il 18/03/2014 17:23, Luiz Capitulino ha scritto:
> On Tue, 18 Mar 2014 15:36:45 +0100
> Jan Kiszka <jan.kiszka@siemens.com> wrote:
>
>>>> Right, this belongs in the "if (env->hflags & HF_LMA_MASK)" block.
>>>>
>>>> And the subject or description should mention that
>>>> x86_cpu_get_phys_page_debug was lacking support for 1G hugepages.
>>>
>>> To be honest, although the PS bit is set and that indicates a 1GB page,
>>> I didn't know Linux does that. I thought Linux would use 4KB pages for
>>> everything unless it's explicitly asked to use bigger pages. Also, note that
>>> I was using gdb to debug really early kernel boot code (start_kernel()).
>>
>> I could imagine that Linux initially creates a giant identity mapping
>> page table for the startup process and only later on switches to
>> fine-grained tables of 4K and 2M pages. Giant pages still require
>> hughtlbfs, IIRC.
>>
>>>
>>> I'd feel more confident to have such a changelog after I find out where
>>> exactly Linux sets that bit, but I won't have time in the next days. On the
>>> other hand, the patch does fix the problem to me.
>>
>> Don't worry about Linux (the code should work with any OS anyway), just
>> believe your reviewers. ;) Alternatively, check Intel IA32 SDM on page
>> table structures.
>
> OK, so you want me to change the subject? Anything else for v2?

You only need to move the new code into the "if (env->hflags & 
HF_LMA_MASK)", I think.  The subject is ok.

Paolo