Re: [Xen-devel] xen/arm: Crash when allocating memory for ACPI table (Was Re: Design doc of adding ACPI support for arm64 on Xen - version 2)

[Shannon Zhao <shannon.zhao@xxxxxxxxxx>]

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

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