Re: [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@xxxxxxxxx wrote:
From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>

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@xxxxxxxxx>
Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
---
  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@xxxxxxxxxx>




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