When starting multi-core loongarch virtualization on loongarch physical machine, loading livepatch on the physical machine will cause an error similar to the following: [ 411.686289] livepatch: klp_try_switch_task: CPU 31/KVM:3116 has an unreliable stack
The specific test steps are as follows: 1.Start a multi-core virtual machine on a physical machine
2.Enter the following command on the physical machine to turn on the debug switch: echo "file kernel/livepatch/transition.c +p" > /sys/kernel/debug/\ dynamic_debug/control
3.Load livepatch: modprobe livepatch-sample
Through the above steps, similar prints can be viewed in dmesg.
The reason for this issue is that the code of the kvm_exc_entry function was copied in the function kvm_loongarch_env_init. When the cpu needs to execute kvm_exc_entry, it will switch to the copied address for execution. The new address of the kvm_exc_entry function cannot be recognized in ORC, which eventually leads to the arch_stack_walk_reliable function returning an error and printing an exception message.
To solve the above problems, we directly compile the switch.S file into the kernel instead of the module. In this way, the function kvm_exc_entry will no longer need to be copied.
changlog: V3<-V2: 1.Replace the EXPORT_SYMBOL macro declaration symbol with the EXPORT_SYMBOL_FOR_KVM macro
2.Add some comments in kvm_enter_guest
3.Place the correct pc address in era
4.Move .p2align after .text
V2<-V1: 1.Rollback the modification of function parameter types such as kvm_save_fpu. In the asm-prototypes.h header file, only the parameter types it depends on are included
Cc: Huacai Chen chenhuacai@kernel.org Cc: WANG Xuerui kernel@xen0n.name Cc: Tianrui Zhao zhaotianrui@loongson.cn Cc: Bibo Mao maobibo@loongson.cn Cc: Charlie Jenkins charlie@rivosinc.com Cc: Xianglai Li lixianglai@loongson.cn Cc: Thomas Gleixner tglx@linutronix.de Cc: stable@vger.kernel.org Cc: Tiezhu Yang yangtiezhu@loongson.cn
Xianglai Li (2): LoongArch: KVM: Compile the switch.S file directly into the kernel LoongArch: KVM: fix "unreliable stack" issue
arch/loongarch/Kbuild | 2 +- arch/loongarch/include/asm/asm-prototypes.h | 21 +++++++++++++ arch/loongarch/include/asm/kvm_host.h | 3 -- arch/loongarch/kvm/Makefile | 2 +- arch/loongarch/kvm/main.c | 35 ++------------------- arch/loongarch/kvm/switch.S | 32 ++++++++++++++++--- 6 files changed, 53 insertions(+), 42 deletions(-)
base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8