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


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