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Message-ID: <CAAhV-H5mJTZgGNHoxbH0TNLg5iQ0fHmOHBqFY=Tk_s0A1GeqWg@mail.gmail.com>
Date: Sat, 4 Jan 2025 22:07:04 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Bibo Mao <maobibo@...ngson.cn>
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 v2] LoongArch: KVM: Add hypercall service support for
usermode VMM
On Fri, Jan 3, 2025 at 10:31 AM 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 lets all six registers visiable to VMM.
>
> Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
> ---
> v1 ... v2:
> 1. Add function kvm_complete_user_service() when finish hypercall
> in user-mode VMM and continue to run.
> 2. Add hypercall_exits stat information.
> ---
> arch/loongarch/include/asm/kvm_host.h | 1 +
> arch/loongarch/include/asm/kvm_para.h | 2 ++
> arch/loongarch/include/asm/kvm_vcpu.h | 1 +
> arch/loongarch/include/uapi/asm/kvm_para.h | 1 +
> arch/loongarch/kvm/exit.c | 30 ++++++++++++++++++++++
> arch/loongarch/kvm/vcpu.c | 3 ++-
> 6 files changed, 37 insertions(+), 1 deletion(-)
>
> 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
Queued but rename KVM_HCALL_CODE_USER to KVM_HCALL_CODE_USER_SERVICE
to keep consistency, thanks.
Huacai
>
> #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/asm/kvm_vcpu.h b/arch/loongarch/include/asm/kvm_vcpu.h
> index d7e8f7d50ee0..2c349f961bfb 100644
> --- a/arch/loongarch/include/asm/kvm_vcpu.h
> +++ b/arch/loongarch/include/asm/kvm_vcpu.h
> @@ -43,6 +43,7 @@ int kvm_emu_mmio_read(struct kvm_vcpu *vcpu, larch_inst inst);
> int kvm_emu_mmio_write(struct kvm_vcpu *vcpu, larch_inst inst);
> int kvm_complete_mmio_read(struct kvm_vcpu *vcpu, struct kvm_run *run);
> int kvm_complete_iocsr_read(struct kvm_vcpu *vcpu, struct kvm_run *run);
> +int kvm_complete_user_service(struct kvm_vcpu *vcpu, struct kvm_run *run);
> int kvm_emu_idle(struct kvm_vcpu *vcpu);
> int kvm_pending_timer(struct kvm_vcpu *vcpu);
> int kvm_handle_fault(struct kvm_vcpu *vcpu, int fault);
> 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..70b5ed1241c4 100644
> --- a/arch/loongarch/kvm/exit.c
> +++ b/arch/loongarch/kvm/exit.c
> @@ -538,6 +538,13 @@ int kvm_complete_mmio_read(struct kvm_vcpu *vcpu, struct kvm_run *run)
> return er;
> }
>
> +int kvm_complete_user_service(struct kvm_vcpu *vcpu, struct kvm_run *run)
> +{
> + update_pc(&vcpu->arch);
> + kvm_write_reg(vcpu, LOONGARCH_GPR_A0, run->hypercall.ret);
> + return 0;
> +}
> +
> int kvm_emu_mmio_write(struct kvm_vcpu *vcpu, larch_inst inst)
> {
> int idx, ret;
> @@ -873,6 +880,29 @@ 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->stat.hypercall_exits++;
> + 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..888480a5bc25 100644
> --- a/arch/loongarch/kvm/vcpu.c
> +++ b/arch/loongarch/kvm/vcpu.c
> @@ -1735,7 +1735,8 @@ 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_complete_user_service(vcpu, run);
>
> if (!vcpu->wants_to_run)
> return r;
>
> base-commit: fc033cf25e612e840e545f8d5ad2edd6ba613ed5
> --
> 2.39.3
>
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