Re: [PATCH v3 6/6] x86/vmware: Add TDX hypercall support

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On 12/19/23 3:23 PM, kirill.shutemov@xxxxxxxxxxxxxxx wrote:
On Tue, Dec 19, 2023 at 01:57:51PM -0800, Alexey Makhalov wrote:
diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index 3aa1adaed18f..ef07ab7a07e1 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -428,6 +428,30 @@ static bool __init vmware_legacy_x2apic_available(void)
  		(eax & BIT(VCPU_LEGACY_X2APIC));
  }
+#ifdef CONFIG_INTEL_TDX_GUEST
+unsigned long vmware_tdx_hypercall(unsigned long cmd,
+				   struct tdx_module_args *args)
+{
+	if (!hypervisor_is_type(X86_HYPER_VMWARE))
+		return 0;
+
+	if (cmd & ~VMWARE_CMD_MASK) {
+		pr_warn("Out of range command %x\n", cmd);
+		return 0;

Is zero success? Shouldn't it be an error?

VMware hypercalls do not have a standard way of signalling an error.
To generalize expectations from the caller perspective of any existing hypercalls: error (including hypercall is not supported or disabled) is when return value is 0 and out1/2 are unchanged or equal to in1/in2.

All existing vmware_hypercall callers will gracefully handle returned 0.
But they should never hit this path, as 0 bail out was introduced as a protection for the case where exported vmware_tdx_hypercall is used by random caller (not following VMware hypercall ABI).


+	}
+
+	args->r10 = VMWARE_TDX_VENDOR_LEAF;
+	args->r11 = VMWARE_TDX_HCALL_FUNC;
+	args->r12 = VMWARE_HYPERVISOR_MAGIC;
+	args->r13 = cmd;
+
+	__tdx_hypercall(args);
+
+	return args->r12;
+}
+EXPORT_SYMBOL_GPL(vmware_tdx_hypercall);
+#endif
+
  #ifdef CONFIG_AMD_MEM_ENCRYPT
  static void vmware_sev_es_hcall_prepare(struct ghcb *ghcb,
  					struct pt_regs *regs)
--
2.39.0






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