From mboxrd@z Thu Jan  1 00:00:00 1970
From: Shannon Zhao <shannon.zhao@linaro.org>
Subject: Re: xen/arm: Crash when allocating memory for ACPI
 table (Was Re: Design doc of adding ACPI support for arm64 on Xen - version
 2)
Date: Fri, 14 Aug 2015 22:35:41 +0800
Message-ID: <55CDFCBD.608@linaro.org>
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To: Julien Grall <julien.grall@citrix.com>, Shannon Zhao <zhaoshenglong@huawei.com>, xen-devel <xen-devel@lists.xen.org>, Jan Beulich <jbeulich@suse.com>, Stefano Stabellini <stefano.stabellini@citrix.com>, Ian Campbell <ian.campbell@citrix.com>, Parth Dixit <parth.dixit@linaro.org>, Christoffer Dall <christoffer.dall@linaro.org>
Cc: Hangaohuai <hangaohuai@huawei.com>, "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
List-Id: xen-devel@lists.xenproject.org

Hi Julien,

On 2015/8/14 22:17, Julien Grall wrote:
> (Renaming the subject)
>
> Hi Shannon,
>
> On 14/08/15 15:05, Shannon Zhao wrote:
>>
>>
>> On 2015/8/12 17:11, Julien Grall wrote:
>>> On 12/08/2015 08:22, Shannon Zhao wrote:
>>>> Hi,
>>>
>>> Hi Shannon,
>>>
>>> It's not part of the design discussion and we are avoiding to mix
>>> discussion. Can you please create another thread (or at least renaming
>>> the subject)?
>>>
>>>> I'm working on re-spinning this patchset while encountering a werid
>>>> problem about xzalloc_bytes.
>>>>
>>>> Since I need to copy some ACPI tables, I need to allocate some memory
>>>> for it. So there are a few places calling xzalloc_bytes. And it fails at
>>>> the fifth one. The log is shown as following:
>>>
>>> Do you copy data in the newly allocated memory between 2 xzalloc_bytes?
>>>
>>
>> No, I just use xzalloc_bytes to allocate some place and copy ACPI to the
>> allocated place, modify the content, then call
>> raw_copy_to_guest_flush_dcache to copy the modified tables to guest memory.
>
> Can you provide the code and show which call is crashing?
>
Oh, sorry. The code is not on hand as it stays at my working computer.
 From previous debug, it fails at the xzalloc_bytes. Because I add two 
printk before and after the xzalloc_bytes, only the before one shows.

The code calling route is like below:

acpi_create_fadt();
acpi_create_gtdt();
acpi_create_madt();
acpi_create_stao();
acpi_create_xsdt();
acpi_map_rsdp();
acpi_map_rest_table();
acpi_create_est();
acpi_create_mmap();
...

Within everyone of these functions, it will call xzalloc_bytes to 
allocate memory and call raw_copy_to_guest_flush_dcache to copy the 
modified tables to guest memory. And this failure happened at 
acpi_create_xsdt().

If I add xzalloc_bytes(1000) before acpi_create_xsdt() like below:

acpi_create_fadt();
acpi_create_gtdt();
acpi_create_madt();
acpi_create_stao();

xzalloc_bytes(1000);

acpi_create_xsdt();
acpi_map_rsdp();
acpi_map_rest_table();
acpi_create_est();
acpi_create_mmap();
...

The failure will not happen at acpi_create_xsdt() but at acpi_create_mmap().

-- 
Shannon