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Re: [Qemu-devel] Memory read/write issues
From: |
Andreas Färber |
Subject: |
Re: [Qemu-devel] Memory read/write issues |
Date: |
Sun, 27 Nov 2011 23:16:01 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:8.0) Gecko/20111105 Thunderbird/8.0 |
Am 27.11.2011 15:17, schrieb Avi Kivity:
> On 11/27/2011 04:07 PM, Andreas Färber wrote:
>> Thanks a lot! You were right, setting TARGET_PAGE_BITS to 8 solves this
>> issue.
>>
>> I'd still like to fix this subpage case for others' benefit. Do you have
>> any pointer where I should set breakpoints / review code?
>
> The subpage code (scheduled for demolition in 1.1) lives in exec.c. See
> subpage_init() and subpage_register(). I'd start with enabling
> DEBUG_SUBPAGE, fixing all the build errors, and looking at the output of
> subpage_readlen() and subpage_writelen().
With these hints I've figured out what's actually happening here:
subpage_writelen() is reading a wrong index 2 == IO_MEM_UNASSIGNED from
subpage_t and performing an unassigned memory write, confirmed by
DEBUG_UNASSIGNED.
In subpage_register(), we're taking the (memory & ~TARGET_PAGE_MASK) ==
IO_MEM_RAM path and setting IO_MEM_UNASSIGNED in subpage_t.
Will investigate further tomorrow.
Andreas