Re: [PATCH v19 097/130] KVM: x86: Split core of hypercall emulation to helper function

Binbin Wu
2024-04-09T09:28:10Z

On 2/26/2024 4:26 PM, isaku.yamahata@intel.com wrote:
> From: Sean Christopherson <sean.j.christopherson@intel.com>
>
> By necessity, TDX will use a different register ABI for hypercalls.
> Break out the core functionality so that it may be reused for TDX.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> ---
> arch/x86/include/asm/kvm_host.h | 4 +++
> arch/x86/kvm/x86.c | 56 ++++++++++++++++++++++-----------
> 2 files changed, 42 insertions(+), 18 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index e0ffef1d377d..bb8be091f996 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -2177,6 +2177,10 @@ static inline void kvm_clear_apicv_inhibit(struct kvm *kvm,
> kvm_set_or_clear_apicv_inhibit(kvm, reason, false);
> }
>
> +unsigned long __kvm_emulate_hypercall(struct kvm_vcpu *vcpu, unsigned long nr,
> + unsigned long a0, unsigned long a1,
> + unsigned long a2, unsigned long a3,
> + int op_64_bit, int cpl);
> int kvm_emulate_hypercall(struct kvm_vcpu *vcpu);
>
> int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, u64 error_code,
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index fb7597c22f31..03950368d8db 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -10073,26 +10073,15 @@ static int complete_hypercall_exit(struct kvm_vcpu *vcpu)
> return kvm_skip_emulated_instruction(vcpu);
> }
>
> -int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
> +unsigned long __kvm_emulate_hypercall(struct kvm_vcpu *vcpu, unsigned long nr,
> + unsigned long a0, unsigned long a1,
> + unsigned long a2, unsigned long a3,
> + int op_64_bit, int cpl)
> {
> - unsigned long nr, a0, a1, a2, a3, ret;
> - int op_64_bit;
> -
> - if (kvm_xen_hypercall_enabled(vcpu->kvm))
> - return kvm_xen_hypercall(vcpu);
> -
> - if (kvm_hv_hypercall_enabled(vcpu))
> - return kvm_hv_hypercall(vcpu);
> -
> - nr = kvm_rax_read(vcpu);
> - a0 = kvm_rbx_read(vcpu);
> - a1 = kvm_rcx_read(vcpu);
> - a2 = kvm_rdx_read(vcpu);
> - a3 = kvm_rsi_read(vcpu);
> + unsigned long ret;
>
> trace_kvm_hypercall(nr, a0, a1, a2, a3);
>
> - op_64_bit = is_64_bit_hypercall(vcpu);
> if (!op_64_bit) {
> nr &= 0xFFFFFFFF;
> a0 &= 0xFFFFFFFF;
> @@ -10101,7 +10090,7 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
> a3 &= 0xFFFFFFFF;
> }
>
> - if (static_call(kvm_x86_get_cpl)(vcpu) != 0) {
> + if (cpl) {
> ret = -KVM_EPERM;
> goto out;
> }
> @@ -10162,18 +10151,49 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
>
> WARN_ON_ONCE(vcpu->run->hypercall.flags & KVM_EXIT_HYPERCALL_MBZ);
> vcpu->arch.complete_userspace_io = complete_hypercall_exit;
> + /* stat is incremented on completion. */
> return 0;
> }
> default:
> ret = -KVM_ENOSYS;
> break;
> }
> +
> out:
> + ++vcpu->stat.hypercalls;
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(__kvm_emulate_hypercall);
> +
> +int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
> +{
> + unsigned long nr, a0, a1, a2, a3, ret;
> + int op_64_bit;

Can it be opportunistically changed to bool type, as well as the
argument type of "op_64_bit" in __kvm_emulate_hypercall()?

> + int cpl;
> +
> + if (kvm_xen_hypercall_enabled(vcpu->kvm))
> + return kvm_xen_hypercall(vcpu);
> +
> + if (kvm_hv_hypercall_enabled(vcpu))
> + return kvm_hv_hypercall(vcpu);
> +
> + nr = kvm_rax_read(vcpu);
> + a0 = kvm_rbx_read(vcpu);
> + a1 = kvm_rcx_read(vcpu);
> + a2 = kvm_rdx_read(vcpu);
> + a3 = kvm_rsi_read(vcpu);
> + op_64_bit = is_64_bit_hypercall(vcpu);
> + cpl = static_call(kvm_x86_get_cpl)(vcpu);
> +
> + ret = __kvm_emulate_hypercall(vcpu, nr, a0, a1, a2, a3, op_64_bit, cpl);
> + if (nr == KVM_HC_MAP_GPA_RANGE && !ret)
> + /* MAP_GPA tosses the request to the user space. */
> + return 0;
> +
> if (!op_64_bit)
> ret = (u32)ret;
> kvm_rax_write(vcpu, ret);
>
> - ++vcpu->stat.hypercalls;
> return kvm_skip_emulated_instruction(vcpu);
> }
> EXPORT_SYMBOL_GPL(kvm_emulate_hypercall);