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Message-ID: <CAAhV-H42D4Rybzkc9YVsjo+GEQwiq4LTdjtmWyOzaqmuW6x8CQ@mail.gmail.com>
Date: Mon, 23 Dec 2024 17:05:05 +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] LoongArch: KVM: Add hypercall service support for
usermode VMM
I also tried to port an untested version, but I think your version is
a tested one.
https://github.com/chenhuacai/linux/commit/e6596b0e45c80756794aba74ac086c5c0e0306eb
And I have some questions:
1, "user service" is not only for syscall, so you rename it?
2, Why 4.19 doesn't need something like "vcpu->run->hypercall.args[0]
= kvm_read_reg(vcpu, LOONGARCH_GPR_A0);"
3, I think my version about "vcpu->run->exit_reason =
KVM_EXIT_HYPERCALL;" and "update_pc()" is a little better than yours,
so you can improve them.
Huacai
On Mon, Dec 23, 2024 at 4:54 PM bibo mao <maobibo@...ngson.cn> wrote:
>
>
>
> 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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