[<0>] kvm_emu_idle+0xd4/0xf0 [kvm]
     [<0>] kvm_handle_gspr+0x7c/0x700 [kvm]
     [<0>] kvm_handle_exit+0x160/0x270 [kvm]
     [<0>] kvm_exc_entry+0x104/0x1e4


In "part 1", after executing kvm_enter_guest, the cpu switches from 
root-mode to guest-mode.
In this case, stack backtracking is indeed very rare.

In "part 2", the cpu switches from the guest-mode to the root-mode,
and most of the stack backtracking occurs during this phase.

To obtain the longest call chain, we save pc in kvm_enter_guest to 
pt_regs.csr_era,
and after restoring the sp of the root-mode cpu in kvm_exc_entry,
The ORC entry was re-established using "UNWIND_HINT_REGS",
  and then we obtained the following stack backtrace as we wanted:

     [<0>] kvm_vcpu_block+0x88/0x120 [kvm]
     [<0>] kvm_vcpu_halt+0x68/0x580 [kvm]
     [<0>] kvm_emu_idle+0xd4/0xf0 [kvm]
     [<0>] kvm_handle_gspr+0x7c/0x700 [kvm]
     [<0>] kvm_handle_exit+0x160/0x270 [kvm]
     [<0>] kvm_exc_entry+0x104/0x1e4
     [<0>] kvm_enter_guest+0x38/0x11c
     [<0>] kvm_arch_vcpu_ioctl_run+0x26c/0x498 [kvm]
     [<0>] kvm_vcpu_ioctl+0x200/0xcf8 [kvm]
     [<0>] sys_ioctl+0x498/0xf00
     [<0>] do_syscall+0x98/0x1d0
     [<0>] handle_syscall+0xb8/0x158

Doing so is equivalent to ignoring the details of the cpu root-mode and 
guest-mode switching.
About what you said in the IE enable phase is dangerous,
interrupts are always off during the cpu root-mode and guest-mode 
switching in kvm_enter_guest and kvm_exc_entry.

Thanks!
Xianglai.[PATCH V3 2/2] LoongArch: KVM: fix "unreliable stack" issuelixianglai <lixianglai@loongson.cn> undefinedJinyang He <hejinyang@loongson.cn>, loongarch@lists.linux.dev, linux-kernel@vger.kernel.org, kvm@vger.kernel.org undefined undefined undefined undefined undefined undefined undefined undefined undefined undefined undefined undefinedÊ.„Þ1