Dear 项晨东

On Sat, Apr 23, 2022 at 3:57 PM 项晨东 <xcd19@mails.tsinghua.edu.cn> wrote:

> Dear qemu developers:
> hello~ I'm Xiang Chen dong, a student from Tsinghua University. recently I
> am trying to  accomplish new X86 feature named user-interrupts which can
> view here
> <https://www.intel.com/content/dam/develop/external/us/en/documents/architecture-instruction-set-extensions-programming-reference.pdf>
> .
> I worked for a couple of time, reaching status that new msrs added and
> access of msrs is work well, also add new CPUID infos to qemu64, also I
> could catch new instructions by modify `translate.c` file. my code could
> find here <https://github.com/Xiang-cd/qemu>, the correspond linux kernel
> version could find here <https://github.com/intel/uintr-linux-kernel>.
> but now I have some problems when trying to accomplish instructions named
> SENDUIPI and UIRET.
> for SENDUIPI, the main function of it is sending the user-interrupts. the
> detail way is, machine access memory(address saved in new msr), then read
> another address from memory, then write some content to this memory. I read
> the qemu source code, find a lot of functions like tcg_gen_qemu_ld,  but
> when i click into it from IDE(vscode), i could not find where the function
> body(maybe due to the macro). So I don't understand how the function works
> and how can I wirte a new function to access guest machine memory and write
> back in qemu.
>

    tcg_frontend: gen_op_ld_v-->tcg_gen_qemu_ld_tl-->tcg_gen_qemu_ld_i64
(tcg/tcg-op.c)-->gen_ldst_i64
    tcg_backend: case INDEX_op_qemu_ld_i64:-->tcg_out_qemu_ld
(tcg-target.c.inc tcg/i386)
    You only need to focus on the frontend and learn from how to translate
other instructions.

another problem is that I am not quite get the idea of accomplishment of
> Interrupt, i could find functions like raise_interrupt and raise_exception,
> but I don't understand how it interact with apic(how the control flow
> switched to other functions, i find cpu_loop_exit_restore, but can not find
> the function body), either how the interrupt handled.
>

    hardware interrupt produce
pc_i8259_create-->i8259_init-->x86_allocate_cpu_irq-->pic_irq_request
pic_irq_request-->cpu_interrupt(cs, CPU_INTERRUPT_HARD)
-->softmmu/cpus.c/cpu_interrupt-->tcg_handle_interrupt
  -->cpu_reset_interrupt-->hw/core/cpu-common.c/cpu_reset_interrupt

     hardware interrupt handle
cpu_exec-->cpu_handle_interrupt-->cc->tcg_ops->cpu_exec_interrupt-->x86_cpu_exec_interrupt
-->cpu_get_pic_interrupt-->pic_read_irq
-->do_interrupt_x86_hardirq-->do_interrupt_all-->do_interrupt_protected-->
use siglongjmp or sigsetjmp

    exception handle
cpu_handle_exception-->cc->tcg_ops->fake_user_interrupt-->x86_cpu_do_interrupt-->do_interrupt_all


>
>
the problem is difficult in some ways, I discussed with my classmates and
> friends, but there is no answer.
> so I'm hoping to get important information from you. Is my way of reading
> code right? Is there any tools for development(finding the function
> body)？How can I accomplish this quickly？
> thank you very very much！
> best wishes！
> Xiang Chen Dong
>

Everything here maybe have some mistakes.
Hope it is useful for you.
-- 
best wishes！

Wei Li