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

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Date: Tue, 5 Dec 2023 16:43:16 -0600
From: Tim Merrifield <tim.merrifield@...adcom.com>
To: Alexey Makhalov <alexey.makhalov@...adcom.com>
Cc: Dave Hansen <dave.hansen@...el.com>, Borislav Petkov <bp@...en8.de>, 
	Alexey Makhalov <amakhalov@...are.com>, linux-kernel@...r.kernel.org, 
	virtualization@...ts.linux.dev, hpa@...or.com, dave.hansen@...ux.intel.co, 
	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

Hi Dave and Alexey,

Regarding VMware-specific checks, it may be beneficial to add some
additional checks
such as ensuring that the hypervisor vendor is VMware,
r12==VMWARE_HYPERVISOR_MAGIC,
r10==VMWARE_TDX_VENDOR_LEAF, r11==VMWARE_TDX_HCALL_FUNC and r13 (command) is
restricted to those few commands we expect to be invoked from the
kernel or drivers by VMware-specific
code.

If we add these checks, would folks be OK with exporting this function?


On Tue, Dec 5, 2023 at 3:41 PM Alexey Makhalov
<alexey.makhalov@...adcom.com> wrote:
>
>
>
> 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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