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Message-ID: <204f743d-2901-4ad2-bbcc-a7857a8644e7@broadcom.com>
Date:   Tue, 5 Dec 2023 13:41:22 -0800
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Subject: Re: [PATCH v2 6/6] x86/vmware: Add TDX hypercall support
To:     Dave Hansen <dave.hansen@intel.com>,
        Borislav Petkov <bp@alien8.de>,
        Alexey Makhalov <amakhalov@vmware.com>
Cc:     linux-kernel@vger.kernel.org, virtualization@lists.linux.dev,
        hpa@zytor.com, dave.hansen@linux.intel.co, bp@alien8.d,
        mingo@redhat.com, tglx@linutronix.de, x86@kernel.org,
        netdev@vger.kernel.org, richardcochran@gmail.com,
        linux-input@vger.kernel.org, dmitry.torokhov@gmail.com,
        zackr@vmware.com, linux-graphics-maintainer@vmware.com,
        pv-drivers@vmware.com, namit@vmware.com, timothym@vmware.com,
        akaher@vmware.com, jsipek@vmware.com,
        dri-devel@lists.freedesktop.org, daniel@ffwll.ch,
        airlied@gmail.com, tzimmermann@suse.de, mripard@kernel.org,
        maarten.lankhorst@linux.intel.com, horms@kernel.org
References: <20231122233058.185601-8-amakhalov@vmware.com>
 <20231201232452.220355-1-amakhalov@vmware.com>
 <20231201232452.220355-7-amakhalov@vmware.com>
 <20231204103100.GYZW2qZE9tbGMtuVgY@fat_crate.local>
 <c2519c9a-8518-403a-9bca-cb79a5f2a6e9@intel.com>
From:   Alexey Makhalov <alexey.makhalov@broadcom.com>
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In-Reply-To: <c2519c9a-8518-403a-9bca-cb79a5f2a6e9@intel.com>
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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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