Re: [PATCH] LoongArch: KVM: Add hypercall service support for usermode VMM

[bibo mao]

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@xxxxxxxxxxx> 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@xxxxxxxxxxx>
> > ---
> >   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