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Message-ID: <d186408c-f083-2404-de60-2ec3c8b528cf@loongson.cn>
Date: Mon, 23 Dec 2024 16:53:57 +0800
From: bibo mao <maobibo@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>
Cc: Tianrui Zhao <zhaotianrui@...ngson.cn>, WANG Xuerui <kernel@...0n.name>,
kvm@...r.kernel.org, loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] LoongArch: KVM: Add hypercall service support for
usermode VMM
On 2024/12/23 下午4:50, Huacai Chen wrote:
> Hi, Bibo,
>
> Is this patch trying to do the same thing as "LoongArch: add hypcall
> to emulate syscall in kvm" in 4.19?
yes, it is to do so -:)
Regards
Bibo Mao
>
> Huacai
>
> On Mon, Dec 23, 2024 at 4:42 PM Bibo Mao <maobibo@...ngson.cn> wrote:
>>
>> Some VMMs provides special hypercall service in usermode, KVM need
>> not handle the usermode hypercall service and pass it to VMM and
>> let VMM handle it.
>>
>> Here new code KVM_HCALL_CODE_USER is added for user-mode hypercall
>> service, KVM loads all six registers to VMM.
>>
>> Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
>> ---
>> arch/loongarch/include/asm/kvm_host.h | 1 +
>> arch/loongarch/include/asm/kvm_para.h | 2 ++
>> arch/loongarch/include/uapi/asm/kvm_para.h | 1 +
>> arch/loongarch/kvm/exit.c | 22 ++++++++++++++++++++++
>> arch/loongarch/kvm/vcpu.c | 3 +++
>> 5 files changed, 29 insertions(+)
>>
>> diff --git a/arch/loongarch/include/asm/kvm_host.h b/arch/loongarch/include/asm/kvm_host.h
>> index 7b8367c39da8..590982cd986e 100644
>> --- a/arch/loongarch/include/asm/kvm_host.h
>> +++ b/arch/loongarch/include/asm/kvm_host.h
>> @@ -162,6 +162,7 @@ enum emulation_result {
>> #define LOONGARCH_PV_FEAT_UPDATED BIT_ULL(63)
>> #define LOONGARCH_PV_FEAT_MASK (BIT(KVM_FEATURE_IPI) | \
>> BIT(KVM_FEATURE_STEAL_TIME) | \
>> + BIT(KVM_FEATURE_USER_HCALL) | \
>> BIT(KVM_FEATURE_VIRT_EXTIOI))
>>
>> struct kvm_vcpu_arch {
>> diff --git a/arch/loongarch/include/asm/kvm_para.h b/arch/loongarch/include/asm/kvm_para.h
>> index c4e84227280d..d3c00de484f6 100644
>> --- a/arch/loongarch/include/asm/kvm_para.h
>> +++ b/arch/loongarch/include/asm/kvm_para.h
>> @@ -13,12 +13,14 @@
>>
>> #define KVM_HCALL_CODE_SERVICE 0
>> #define KVM_HCALL_CODE_SWDBG 1
>> +#define KVM_HCALL_CODE_USER 2
>>
>> #define KVM_HCALL_SERVICE HYPERCALL_ENCODE(HYPERVISOR_KVM, KVM_HCALL_CODE_SERVICE)
>> #define KVM_HCALL_FUNC_IPI 1
>> #define KVM_HCALL_FUNC_NOTIFY 2
>>
>> #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)
>>
>> /*
>> * LoongArch hypercall return code
>> diff --git a/arch/loongarch/include/uapi/asm/kvm_para.h b/arch/loongarch/include/uapi/asm/kvm_para.h
>> index b0604aa9b4bb..76d802ef01ce 100644
>> --- a/arch/loongarch/include/uapi/asm/kvm_para.h
>> +++ b/arch/loongarch/include/uapi/asm/kvm_para.h
>> @@ -17,5 +17,6 @@
>> #define KVM_FEATURE_STEAL_TIME 2
>> /* BIT 24 - 31 are features configurable by user space vmm */
>> #define KVM_FEATURE_VIRT_EXTIOI 24
>> +#define KVM_FEATURE_USER_HCALL 25
>>
>> #endif /* _UAPI_ASM_KVM_PARA_H */
>> diff --git a/arch/loongarch/kvm/exit.c b/arch/loongarch/kvm/exit.c
>> index a7893bd01e73..1a85cd4fb6a5 100644
>> --- a/arch/loongarch/kvm/exit.c
>> +++ b/arch/loongarch/kvm/exit.c
>> @@ -873,6 +873,28 @@ static int kvm_handle_hypercall(struct kvm_vcpu *vcpu)
>> vcpu->stat.hypercall_exits++;
>> kvm_handle_service(vcpu);
>> break;
>> + case KVM_HCALL_USER_SERVICE:
>> + if (!kvm_guest_has_pv_feature(vcpu, KVM_FEATURE_USER_HCALL)) {
>> + kvm_write_reg(vcpu, LOONGARCH_GPR_A0, KVM_HCALL_INVALID_CODE);
>> + break;
>> + }
>> +
>> + vcpu->run->exit_reason = KVM_EXIT_HYPERCALL;
>> + vcpu->run->hypercall.nr = KVM_HCALL_USER_SERVICE;
>> + vcpu->run->hypercall.args[0] = kvm_read_reg(vcpu, LOONGARCH_GPR_A0);
>> + vcpu->run->hypercall.args[1] = kvm_read_reg(vcpu, LOONGARCH_GPR_A1);
>> + vcpu->run->hypercall.args[2] = kvm_read_reg(vcpu, LOONGARCH_GPR_A2);
>> + vcpu->run->hypercall.args[3] = kvm_read_reg(vcpu, LOONGARCH_GPR_A3);
>> + vcpu->run->hypercall.args[4] = kvm_read_reg(vcpu, LOONGARCH_GPR_A4);
>> + vcpu->run->hypercall.args[5] = kvm_read_reg(vcpu, LOONGARCH_GPR_A5);
>> + vcpu->run->hypercall.flags = 0;
>> + /*
>> + * Set invalid return value by default
>> + * Need user-mode VMM modify it
>> + */
>> + vcpu->run->hypercall.ret = KVM_HCALL_INVALID_CODE;
>> + 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/vcpu.c b/arch/loongarch/kvm/vcpu.c
>> index d18a4a270415..8c46ad1872ee 100644
>> --- a/arch/loongarch/kvm/vcpu.c
>> +++ b/arch/loongarch/kvm/vcpu.c
>> @@ -1735,6 +1735,9 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
>> if (run->exit_reason == KVM_EXIT_LOONGARCH_IOCSR) {
>> if (!run->iocsr_io.is_write)
>> kvm_complete_iocsr_read(vcpu, run);
>> + } else if (run->exit_reason == KVM_EXIT_HYPERCALL) {
>> + kvm_write_reg(vcpu, LOONGARCH_GPR_A0, run->hypercall.ret);
>> + update_pc(&vcpu->arch);
>> }
>>
>> if (!vcpu->wants_to_run)
>>
>> base-commit: 48f506ad0b683d3e7e794efa60c5785c4fdc86fa
>> --
>> 2.39.3
>>
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