Re: [PATCH v2 3/6] hppa: Add support for an emulated TOC/NMI button.

[Richard Henderson <richard.henderson@linaro.org>]

On 2/1/22 08:35, Helge Deller wrote:
> Almost all PA-RISC machines have either a button that is labeled with 'TOC' or
> a BMC/GSP function to trigger a TOC.  TOC is a non-maskable interrupt that is
> sent to the processor.  This can be used for diagnostic purposes like obtaining
> a stack trace/register dump or to enter KDB/KGDB in Linux.
> 
> This patch adds support for such an emulated TOC button.
> 
> It wires up the qemu monitor "nmi" command to trigger a TOC.  For that it
> provides the hppa_nmi function which is assigned to the nmi_monitor_handler
> function pointer.  When called it raises the EXCP_TOC hardware interrupt in the
> hppa_cpu_do_interrupt() function.  The interrupt function then calls the
> architecturally defined TOC function in SeaBIOS-hppa firmware (at fixed address
> 0xf0000000).
> 
> According to the PA-RISC PDC specification, the SeaBIOS firmware then writes
> the CPU registers into PIM (processor internal memmory) for later analysis.  In
> order to write all registers it needs to know the contents of the CPU "shadow
> registers" and the IASQ- and IAOQ-back values. The IAOQ/IASQ values are
> provided by qemu in shadow registers when entering the SeaBIOS TOC function.
> This patch adds a new aritificial opcode "getshadowregs" (0xfffdead2) which
> restores the original values of the shadow registers. With this opcode SeaBIOS
> can store those registers as well into PIM before calling an OS-provided TOC
> handler.
> 
> To trigger a TOC, switch to the qemu monitor with Ctrl-A C, and type in the
> command "nmi".  After the TOC started the OS-debugger, exit the qemu monitor
> with Ctrl-A C.
> 
> Signed-off-by: Helge Deller<deller@gmx.de>
> ---
>   hw/hppa/machine.c        | 35 ++++++++++++++++++++++++++++++++++-
>   target/hppa/cpu.c        |  2 +-
>   target/hppa/cpu.h        |  5 +++++
>   target/hppa/helper.h     |  1 +
>   target/hppa/insns.decode |  1 +
>   target/hppa/int_helper.c | 19 ++++++++++++++++++-
>   target/hppa/op_helper.c  |  7 ++++++-
>   target/hppa/translate.c  | 10 ++++++++++
>   8 files changed, 76 insertions(+), 4 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~