linux-kernel - Re: [PATCH V2 2/2] LoongArch: KVM: fix "unreliable stack" issue

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <48cfef68-533f-b275-764c-2c00b1631e42@loongson.cn>
Date: Tue, 23 Dec 2025 10:37:34 +0800
From: lixianglai <lixianglai@...ngson.cn>
To: Bibo Mao <maobibo@...ngson.cn>, loongarch@...ts.linux.dev,
 linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc: stable@...r.kernel.org, Huacai Chen <chenhuacai@...nel.org>,
 WANG Xuerui <kernel@...0n.name>, Tianrui Zhao <zhaotianrui@...ngson.cn>,
 Charlie Jenkins <charlie@...osinc.com>, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH V2 2/2] LoongArch: KVM: fix "unreliable stack" issue

Hi Bibo Mao:
>
>
> On 2025/12/22 下午7:34, Xianglai Li wrote:
>> Insert the appropriate UNWIND macro definition into the kvm_exc_entry in
>> the assembly function to guide the generation of correct ORC table 
>> entries,
>> thereby solving the timeout problem of loading the livepatch-sample 
>> module
>> on a physical machine running multiple vcpus virtual machines.
>>
>> While solving the above problems, we have gained an additional benefit,
>> that is, we can obtain more call stack information
>>
>> Stack information that can be obtained before the problem is fixed:
>> [<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+0x100/0x1e0
>>
>> Stack information that can be obtained after the problem is fixed:
>> [<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+0x100/0x1e0
>> [<0>] kvm_arch_vcpu_ioctl_run+0x260/0x488 [kvm]
>> [<0>] kvm_vcpu_ioctl+0x200/0xcd8 [kvm]
>> [<0>] sys_ioctl+0x498/0xf00
>> [<0>] do_syscall+0x94/0x190
>> [<0>] handle_syscall+0xb8/0x158
>>
>> Cc: stable@...r.kernel.org
>> Signed-off-by: Xianglai Li <lixianglai@...ngson.cn>
>> ---
>> Cc: Huacai Chen <chenhuacai@...nel.org>
>> Cc: WANG Xuerui <kernel@...0n.name>
>> Cc: Tianrui Zhao <zhaotianrui@...ngson.cn>
>> Cc: Bibo Mao <maobibo@...ngson.cn>
>> Cc: Charlie Jenkins <charlie@...osinc.com>
>> Cc: Xianglai Li <lixianglai@...ngson.cn>
>> Cc: Thomas Gleixner <tglx@...utronix.de>
>>
>>   arch/loongarch/kvm/switch.S | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/arch/loongarch/kvm/switch.S b/arch/loongarch/kvm/switch.S
>> index 93845ce53651..e3ecb24a3bc5 100644
>> --- a/arch/loongarch/kvm/switch.S
>> +++ b/arch/loongarch/kvm/switch.S
>> @@ -170,6 +170,7 @@ SYM_CODE_START(kvm_exc_entry)
>>       /* restore per cpu register */
>>       ld.d    u0, a2, KVM_ARCH_HPERCPU
>>       addi.d    sp, sp, -PT_SIZE
>> +    UNWIND_HINT_REGS
>>         /* Prepare handle exception */
>>       or    a0, s0, zero
>> @@ -214,6 +215,7 @@ SYM_FUNC_START(kvm_enter_guest)
>>       addi.d    a2, sp, -PT_SIZE
>>       /* Save host GPRs */
>>       kvm_save_host_gpr a2
>> +    st.d    ra, a2, PT_ERA
> Had better add some comments here to show that it is special for 
> unwind usage since there is "st.d ra, a2, PT_R1" already in macro 
> kvm_save_host_gpr().
>
Ok, I will add some comments to explain it in the next version.
Thanks!
Xianglai.
> Regards
> Bibo Mao
>>         addi.d    a2, a1, KVM_VCPU_ARCH
>>       st.d    sp, a2, KVM_ARCH_HSP
>>