Hi Martin,
On 2/18/19 9:01 AM, Martin Schwidefsky wrote:
On Mon, 18 Feb 2019 07:46:40 -0800
Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
Hi,
On Thu, Feb 14, 2019 at 03:40:56PM +0100, Martin Schwidefsky wrote:
The setup_lowcore() function creates a new prefix page for the boot CPU.
The PSW mask for the system_call, external interrupt, i/o interrupt and
the program check handler have the DAT bit set in this new prefix page.
At the time setup_lowcore is called the system still runs without virtual
address translation, the paging_init() function creates the kernel page
table and loads the CR13 with the kernel ASCE.
Any code between setup_lowcore() and the end of paging_init() that has
a BUG or WARN statement will create a program check that can not be
handled correctly as there is no kernel page table yet.
To allow early WARN statements initially setup the lowcore with DAT off
and set the DAT bit only after paging_init() has completed.
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
This patch causes s390 qemu emulations to crash with a kernel stack overflow.
Reverting the patch fixes the problem. Crash log and bisect results below.
Urgs, yes. That is EDAT-1 again that makes it work with 1MB pages but breaks
with 4K mapping where the prefix page is mapped to absolute zero.
Is there some non-default configuration besides defconfig that I could run to
catch both working and non-working images ? I don't immediately see an option
to select the page size.
Thanks,
Guenter
Just using S390_lowcore instead of lowcore_ptr[0] does not work either
because low-address protection is already active. I'll think of something.
Thanks for bug report!
