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    SubjectRe: [RFC PATCH v2 14/69] KVM: x86: Split core of hypercall emulation to helper function
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    On 03/07/21 00:04, 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 | 55 ++++++++++++++++++++-------------
    > 2 files changed, 38 insertions(+), 21 deletions(-)
    >
    > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
    > index 9c7ced0e3171..80b943e4ab6d 100644
    > --- a/arch/x86/include/asm/kvm_host.h
    > +++ b/arch/x86/include/asm/kvm_host.h
    > @@ -1667,6 +1667,10 @@ void kvm_vcpu_update_apicv(struct kvm_vcpu *vcpu);
    > void kvm_request_apicv_update(struct kvm *kvm, bool activate,
    > unsigned long bit);
    >
    > +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 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 d11cf87674f3..795f83a1cf9a 100644
    > --- a/arch/x86/kvm/x86.c
    > +++ b/arch/x86/kvm/x86.c
    > @@ -8406,26 +8406,15 @@ static void kvm_sched_yield(struct kvm_vcpu *vcpu, unsigned long dest_id)
    > return;
    > }
    >
    > -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)
    > {
    > - 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_mode(vcpu);
    > if (!op_64_bit) {
    > nr &= 0xFFFFFFFF;
    > a0 &= 0xFFFFFFFF;
    > @@ -8434,11 +8423,6 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
    > a3 &= 0xFFFFFFFF;
    > }
    >
    > - if (static_call(kvm_x86_get_cpl)(vcpu) != 0) {
    > - ret = -KVM_EPERM;
    > - goto out;
    > - }
    > -
    > ret = -KVM_ENOSYS;
    >
    > switch (nr) {
    > @@ -8475,6 +8459,35 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
    > ret = -KVM_ENOSYS;
    > break;
    > }
    > + 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;
    > +
    > + 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_mode(vcpu);
    > +
    > + if (static_call(kvm_x86_get_cpl)(vcpu) != 0) {
    > + ret = -KVM_EPERM;
    > + goto out;
    > + }
    > +
    > + ret = __kvm_emulate_hypercall(vcpu, nr, a0, a1, a2, a3, op_64_bit);
    > out:
    > if (!op_64_bit)
    > ret = (u32)ret;
    >

    Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

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