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Date: Mon, 22 Jan 2024 10:28:58 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
To: Dave Hansen <dave.hansen@intel.com>,
        Alexey Makhalov <alexey.makhalov@broadcom.com>,
        linux-kernel@vger.kernel.org, virtualization@lists.linux.dev,
        bp@alien8.de, dave.hansen@linux.intel.com, mingo@redhat.com,
        tglx@linutronix.de
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        linux-input@vger.kernel.org, dmitry.torokhov@gmail.com,
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Subject: Re: [PATCH v6 7/7] x86/vmware: Add TDX hypercall support
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On January 22, 2024 8:32:22 AM PST, Dave Hansen <dave=2Ehansen@intel=2Ecom>=
 wrote:
>On 1/9/24 00:40, Alexey Makhalov wrote:
>> +#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 ULONG_MAX;
>> +
>> +	if (cmd & ~VMWARE_CMD_MASK) {
>> +		pr_warn_once("Out of range command %lx\n", cmd);
>> +		return ULONG_MAX;
>> +	}
>> +
>> +	args->r10 =3D VMWARE_TDX_VENDOR_LEAF;
>> +	args->r11 =3D VMWARE_TDX_HCALL_FUNC;
>> +	args->r12 =3D VMWARE_HYPERVISOR_MAGIC;
>> +	args->r13 =3D cmd;
>> +	args->r15 =3D 0; /* CPL */
>> +
>> +	__tdx_hypercall(args);
>> +
>> +	return args->r12;
>> +}
>> +EXPORT_SYMBOL_GPL(vmware_tdx_hypercall);
>> +#endif
>
>This is the kind of wrapper that I was hoping for=2E  Thanks=2E
>
>Acked-by: Dave Hansen <dave=2Ehansen@linux=2Eintel=2Ecom>
>

I'm slightly confused by this TBH=2E

Why are the arguments passed in as a structure, which is modified by the w=
rapper to boot? This is analogous to a system call interface=2E

Furthermore, this is an out-of-line function; it should never be called wi=
th !X86_HYPER_VMWARE or you are introducing overhead for other hypervisors;=
 I believe a pr_warn_once() is in order at least, just as you have for the =
out-of-range test=2E