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

[Tim Merrifield]

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 at broadcom.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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