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

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Message-ID: <204f743d-2901-4ad2-bbcc-a7857a8644e7@broadcom.com>
Date:   Tue, 5 Dec 2023 13:41:22 -0800
From:   Alexey Makhalov <alexey.makhalov@...adcom.com>
To:     Dave Hansen <dave.hansen@...el.com>,
        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 12/5/23 1:24 PM, Dave Hansen wrote:
> 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.

Considering exporting of __tdx_hypercall for random modules is not an 
option, what VMware specific checks you are suggesting?

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