netdev - Re: [PATCH v2 6/6] x86/vmware: Add TDX hypercall support

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Message-ID: <c2519c9a-8518-403a-9bca-cb79a5f2a6e9@intel.com>
Date: Tue, 5 Dec 2023 13:24:31 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: Borislav Petkov <bp@...en8.de>, Alexey Makhalov <amakhalov@...are.com>
Cc: linux-kernel@...r.kernel.org, virtualization@...ts.linux.dev,
 hpa@...or.com, dave.hansen@...ux.intel.co, bp@...en8.d, mingo@...hat.com,
 tglx@...utronix.de, x86@...nel.org, netdev@...r.kernel.org,
 richardcochran@...il.com, linux-input@...r.kernel.org,
 dmitry.torokhov@...il.com, zackr@...are.com,
 linux-graphics-maintainer@...are.com, pv-drivers@...are.com,
 namit@...are.com, timothym@...are.com, akaher@...are.com, jsipek@...are.com,
 dri-devel@...ts.freedesktop.org, daniel@...ll.ch, airlied@...il.com,
 tzimmermann@...e.de, mripard@...nel.org, maarten.lankhorst@...ux.intel.com,
 horms@...nel.org
Subject: Re: [PATCH v2 6/6] x86/vmware: Add TDX hypercall support

On 12/4/23 02:31, Borislav Petkov wrote:
> On Fri, Dec 01, 2023 at 03:24:52PM -0800, Alexey Makhalov wrote:
>> +#ifdef CONFIG_INTEL_TDX_GUEST
>> +/* __tdx_hypercall() is not exported. So, export the wrapper */
>> +void vmware_tdx_hypercall_args(struct tdx_module_args *args)
>> +{
>> +	__tdx_hypercall(args);
>> +}
>> +EXPORT_SYMBOL_GPL(vmware_tdx_hypercall_args);
> Uuuh, lovely. I'd like to see what the TDX folks think about this
> export first.

I don't really like it much.  This does a generic thing (make a TDX
hypercall) with a specific name ("vmware_").  If you want to make an
argument that a certain chunk of the __tdx_hypercall() space is just for
VMWare and you also add a VMWare-specific check and then export *that*,
it might be acceptable.

But I don't want random modules able to make random, unrestricted TDX
hypercalls.  That's asking for trouble.