From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.loongson.cn (mail.loongson.cn [114.242.206.163]) by smtp.subspace.kernel.org (Postfix) with ESMTP id D484231716A; Mon, 12 Oct 2026 00:55:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=114.242.206.163 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791766555; cv=none; b=WJG59B/8WHxiRYfz9h+CGzEfnQzluThzrOOKgjRaK92q+h/MOgcLXinP12TLGSgwP5upeUPqAcideqxptBcWjTxawghEFMT2Wtucav1o+H1mR9U0b4MuFugLdkJflZwE2rk7dZSso7aSIJmm2U/4cX1Id5WGfYYw5RjrjKR6GY8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791766555; c=relaxed/simple; bh=0CNcZKjbQsiWhy99cjgvyC3eghbqlrLAmMYvxBlPEO0=; h=Subject:To:Cc:References:From:Message-ID:Date:MIME-Version: In-Reply-To:Content-Type; b=cW7sIt8iGcw+RLOYrGEfbbD+Jm2KNN7JH3bNbIXdbv2pS0CqoCTLmbwFvqJHkBJk1Vm3LaCd93SVrzHqs2yTZXZB/6pgMsO5oUWop7ng941mfKkZCY8PCgZmGAWohgLASviKE36pQ8rCRANAgM1RcUYwHnF5SCKnhCbUw+0ajCI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=loongson.cn; spf=pass smtp.mailfrom=loongson.cn; arc=none smtp.client-ip=114.242.206.163 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=loongson.cn Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=loongson.cn Received: from loongson.cn (unknown [10.20.42.62]) by gateway (Coremail) with SMTP id _____8DxztIVMMxqs8YUAA--.59952S3; Mon, 12 Oct 2026 08:55:49 +0800 (CST) Received: from [10.20.42.62] (unknown [10.20.42.62]) by front1 (Coremail) with SMTP id qMiowJAxmM0UMMxqDT8rAA--.24843S2; Mon, 12 Oct 2026 08:55:48 +0800 (CST) Subject: Re: [PATCH] LoongArch: KVM: Add hypercall crash support To: Huacai Chen Cc: WANG Xuerui , kvm@vger.kernel.org, loongarch@lists.linux.dev, linux-kernel@vger.kernel.org References: <20260909085350.2046788-1-maobibo@loongson.cn> <82f2c59a-59f5-8e49-f0c5-dc6feb4070df@loongson.cn> From: Bibo Mao Message-ID: Date: Mon, 12 Oct 2026 08:57:10 +0800 User-Agent: Mozilla/5.0 (X11; Linux loongarch64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-CM-TRANSID:qMiowJAxmM0UMMxqDT8rAA--.24843S2 X-CM-SenderInfo: xpdruxter6z05rqj20fqof0/ X-Coremail-Antispam: 1Uk129KBj93XoW3JF43XFWfCr13Wr1DAr17XFc_yoWxKw17pF yvyFs5GrWUGr1fCwsaq3sIgr9xKrsrGr1IgFy2grW8AFn0qFnxZr18tFyDCFn8X348Xa40 vF9Yg343ZFW3t3cCm3ZEXasCq-sJn29KB7ZKAUJUUUU8529EdanIXcx71UUUUU7KY7ZEXa sCq-sGcSsGvfJ3Ic02F40EFcxC0VAKzVAqx4xG6I80ebIjqfuFe4nvWSU5nxnvy29KBjDU 0xBIdaVrnRJUUUvjb4IE77IF4wAFF20E14v26r1j6r4UM7CY07I20VC2zVCF04k26cxKx2 IYs7xG6rWj6s0DM7CIcVAFz4kK6r1Y6r17M28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48v e4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Jr0_JF4l84ACjcxK6xIIjxv20xvEc7CjxVAFwI 0_Jr0_Gr1l84ACjcxK6I8E87Iv67AKxVWUJVW8JwA2z4x0Y4vEx4A2jsIEc7CjxVAFwI0_ Jr0_Gr1le2I262IYc4CY6c8Ij28IcVAaY2xG8wAqjxCEc2xF0cIa020Ex4CE44I27wAqx4 xG64xvF2IEw4CE5I8CrVC2j2WlYx0E2Ix0cI8IcVAFwI0_JrI_JrylYx0Ex4A2jsIE14v2 6r1j6r4UMcvjeVCFs4IE7xkEbVWUJVW8JwACjcxG0xvEwIxGrwCYjI0SjxkI62AI1cAE67 vIY487MxAIw28IcxkI7VAKI48JMxC20s026xCaFVCjc4AY6r1j6r4UMI8I3I0E5I8CrVAF wI0_Jr0_Jr4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE17CEb7AF67AKxVWUAVWUtwCIc4 0Y0x0EwIxGrwCI42IY6xIIjxv20xvE14v26r1j6r1xMIIF0xvE2Ix0cI8IcVCY1x0267AK xVWUJVW8JwCI42IY6xAIw20EY4v20xvaj40_Jr0_JF4lIxAIcVC2z280aVAFwI0_Jr0_Gr 1lIxAIcVC2z280aVCY1x0267AKxVWUJVW8JbIYCTnIWIevJa73UjIFyTuYvjxU70PfDUUU U On 2026/10/11 下午10:06, Huacai Chen wrote: > On Thu, Oct 8, 2026 at 9:50 AM Bibo Mao wrote: >> >> >> >> On 2026/10/3 下午12:02, Huacai Chen wrote: >>> Hi, Bibo, >>> >>> On Wed, Sep 9, 2026 at 5:01 PM Bibo Mao wrote: >>>> >>>> Now generic pvpanic is supported in Linux kernel which will notify VMM >>>> with VM crash event. There is some limitations with pvpanic, such as it >>>> requires good kernel stack or CPU hardware context and panic() C function >>>> is in health state. >>>> >>>> Sometimes CPU hardware context or kernel/irq stack is corrupted. Hypercall >>>> code is more direct and low-level crash method, which is useful in >>>> exception entry with assmble language, here add one hypercall code to >>>> support VM crash function, so that VMM can capture CPU crash context >>>> in time. >>>> >>>> Signed-off-by: Bibo Mao >>>> --- >>>> arch/loongarch/include/asm/kvm_host.h | 1 + >>>> arch/loongarch/include/asm/kvm_para.h | 15 +++++++++++++++ >>>> arch/loongarch/include/uapi/asm/kvm.h | 1 + >>>> arch/loongarch/include/uapi/asm/kvm_para.h | 1 + >>>> arch/loongarch/kvm/exit.c | 11 +++++++++++ >>>> arch/loongarch/kvm/vm.c | 3 ++- >>>> 6 files changed, 31 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/arch/loongarch/include/asm/kvm_host.h b/arch/loongarch/include/asm/kvm_host.h >>>> index 65d91c3ce313..96f9f1317cad 100644 >>>> --- a/arch/loongarch/include/asm/kvm_host.h >>>> +++ b/arch/loongarch/include/asm/kvm_host.h >>>> @@ -168,6 +168,7 @@ enum emulation_result { >>>> #define LOONGARCH_PV_FEAT_MASK (BIT(KVM_FEATURE_IPI) | \ >>>> BIT(KVM_FEATURE_PREEMPT) | \ >>>> BIT(KVM_FEATURE_STEAL_TIME) | \ >>>> + BIT(KVM_FEATURE_CRASH) | \ >>>> BIT(KVM_FEATURE_USER_HCALL) | \ >>>> BIT(KVM_FEATURE_VIRT_EXTIOI)) >>>> >>>> diff --git a/arch/loongarch/include/asm/kvm_para.h b/arch/loongarch/include/asm/kvm_para.h >>>> index fb17ba0fa101..3b183bb1aaa8 100644 >>>> --- a/arch/loongarch/include/asm/kvm_para.h >>>> +++ b/arch/loongarch/include/asm/kvm_para.h >>>> @@ -14,6 +14,7 @@ >>>> #define KVM_HCALL_CODE_SERVICE 0 >>>> #define KVM_HCALL_CODE_SWDBG 1 >>>> #define KVM_HCALL_CODE_USER_SERVICE 2 >>>> +#define KVM_HCALL_CODE_CRASH 3 >>>> >>>> #define KVM_HCALL_SERVICE HYPERCALL_ENCODE(HYPERVISOR_KVM, KVM_HCALL_CODE_SERVICE) >>>> #define KVM_HCALL_FUNC_IPI 1 >>>> @@ -22,6 +23,7 @@ >>>> #define KVM_HCALL_SWDBG HYPERCALL_ENCODE(HYPERVISOR_KVM, KVM_HCALL_CODE_SWDBG) >>>> >>>> #define KVM_HCALL_USER_SERVICE HYPERCALL_ENCODE(HYPERVISOR_KVM, KVM_HCALL_CODE_USER_SERVICE) >>>> +#define KVM_HCALL_CRASH HYPERCALL_ENCODE(HYPERVISOR_KVM, KVM_HCALL_CODE_CRASH) >>>> >>>> /* >>>> * LoongArch hypercall return code >>>> @@ -161,6 +163,19 @@ static __always_inline long kvm_hypercall5(u64 fid, >>>> return ret; >>>> } >>>> >>>> +static __always_inline long kvm_hypercall_crash(void) >>>> +{ >>>> + register long ret asm("a0"); >>>> + >>>> + __asm__ __volatile__( >>>> + "hvcl "__stringify(KVM_HCALL_CRASH) >>>> + : "=r" (ret) >>>> + : : "memory" >>>> + ); >>>> + >>>> + return ret; >>>> +} >>> Why this function has no caller? >> Currently we directly modify guest kernel and hard-code the hypercall >> instruction to debug. This inline function is only example for howto >> usage, the normal usage such as checking KVM_FEATURE_USER_HCALL feature >> + kvm_hypercall_crash() is too complicated in exception entry assemble >> language. > There are no examples for KVM_HCALL_SWDBG and KVM_HCALL_USER_SERVICE, > I think KVM_HCALL_CRASH is no special. > > So if you agree, I will remove this example when applying. Removinge the example usage with KVM_HCALL_CRASH is fine to me. Regards Bibo Mao > > > Huacai > >> >> Regards >> Bibo Mao >>> >>> >>> Huacai >>> >>>> + >>>> #ifdef CONFIG_PARAVIRT >>>> bool kvm_para_available(void); >>>> unsigned int kvm_arch_para_features(void); >>>> diff --git a/arch/loongarch/include/uapi/asm/kvm.h b/arch/loongarch/include/uapi/asm/kvm.h >>>> index cd0b5c11ca9c..b222bfc48042 100644 >>>> --- a/arch/loongarch/include/uapi/asm/kvm.h >>>> +++ b/arch/loongarch/include/uapi/asm/kvm.h >>>> @@ -106,6 +106,7 @@ struct kvm_fpu { >>>> #define KVM_LOONGARCH_VM_FEAT_PTW 8 >>>> #define KVM_LOONGARCH_VM_FEAT_MSGINT 9 >>>> #define KVM_LOONGARCH_VM_FEAT_PV_PREEMPT 10 >>>> +#define KVM_LOONGARCH_VM_FEAT_CRASH 11 >>>> >>>> /* Device Control API on vcpu fd */ >>>> #define KVM_LOONGARCH_VCPU_CPUCFG 0 >>>> diff --git a/arch/loongarch/include/uapi/asm/kvm_para.h b/arch/loongarch/include/uapi/asm/kvm_para.h >>>> index d28cbcadd276..bf1a0c826ca6 100644 >>>> --- a/arch/loongarch/include/uapi/asm/kvm_para.h >>>> +++ b/arch/loongarch/include/uapi/asm/kvm_para.h >>>> @@ -16,6 +16,7 @@ >>>> #define KVM_FEATURE_IPI 1 >>>> #define KVM_FEATURE_STEAL_TIME 2 >>>> #define KVM_FEATURE_PREEMPT 3 >>>> +#define KVM_FEATURE_CRASH 4 >>>> /* BIT 24 - 31 are features configurable by user space vmm */ >>>> #define KVM_FEATURE_VIRT_EXTIOI 24 >>>> #define KVM_FEATURE_USER_HCALL 25 >>>> diff --git a/arch/loongarch/kvm/exit.c b/arch/loongarch/kvm/exit.c >>>> index 4f58e6e2cf86..3b6daa946c76 100644 >>>> --- a/arch/loongarch/kvm/exit.c >>>> +++ b/arch/loongarch/kvm/exit.c >>>> @@ -911,6 +911,17 @@ static int kvm_handle_hypercall(struct kvm_vcpu *vcpu, int ecode) >>>> vcpu->run->hypercall.ret = KVM_HCALL_INVALID_CODE; >>>> ret = RESUME_HOST; >>>> break; >>>> + case KVM_HCALL_CRASH: >>>> + if (!kvm_guest_has_pv_feature(vcpu, KVM_FEATURE_CRASH)) { >>>> + kvm_write_reg(vcpu, LOONGARCH_GPR_A0, KVM_HCALL_INVALID_CODE); >>>> + break; >>>> + } >>>> + >>>> + vcpu->run->exit_reason = KVM_EXIT_SYSTEM_EVENT; >>>> + vcpu->run->system_event.type = KVM_SYSTEM_EVENT_CRASH; >>>> + vcpu->run->system_event.ndata = 0; >>>> + ret = RESUME_HOST; >>>> + break; >>>> case KVM_HCALL_SWDBG: >>>> /* KVM_HCALL_SWDBG only in effective when SW_BP is enabled */ >>>> if (vcpu->guest_debug & KVM_GUESTDBG_SW_BP_MASK) { >>>> diff --git a/arch/loongarch/kvm/vm.c b/arch/loongarch/kvm/vm.c >>>> index 6dabb227a732..e5d10ceb5e67 100644 >>>> --- a/arch/loongarch/kvm/vm.c >>>> +++ b/arch/loongarch/kvm/vm.c >>>> @@ -49,8 +49,9 @@ static void kvm_vm_init_features(struct kvm *kvm) >>>> kvm->arch.kvm_features |= BIT(KVM_LOONGARCH_VM_FEAT_PMU); >>>> >>>> /* Enable all PV features by default */ >>>> - kvm->arch.pv_features |= BIT(KVM_FEATURE_IPI); >>>> + kvm->arch.pv_features |= BIT(KVM_FEATURE_IPI) | BIT(KVM_FEATURE_CRASH); >>>> kvm->arch.kvm_features |= BIT(KVM_LOONGARCH_VM_FEAT_PV_IPI); >>>> + kvm->arch.kvm_features |= BIT(KVM_LOONGARCH_VM_FEAT_CRASH); >>>> if (kvm_pvtime_supported()) { >>>> kvm->arch.pv_features |= BIT(KVM_FEATURE_PREEMPT); >>>> kvm->arch.pv_features |= BIT(KVM_FEATURE_STEAL_TIME); >>>> >>>> base-commit: df2908090cda368b01ff43709f51890076c56157 >>>> -- >>>> 2.39.3 >>>> >>>> >>