Re: [PATCH 07/25] KVM: TDX: Add helper functions to allocate/free TDX private host key id

Edgecombe, Rick P
2024-09-10T16:39:37Z

On Tue, 2024-09-10 at 18:27 +0200, Paolo Bonzini wrote:
> On 8/13/24 00:48, Rick Edgecombe wrote:
> > From: Isaku Yamahata <isaku.yamahata@intel.com>
> >
> > Add helper functions to allocate/free TDX private host key id (HKID).
> >
> > The memory controller encrypts TDX memory with the assigned HKIDs. Each TDX
> > guest must be protected by its own unique TDX HKID.
> >
> > The HW has a fixed set of these HKID keys. Out of those, some are set aside
> > for use by for other TDX components, but most are saved for guest use. The
> > code that does this partitioning, records the range chosen to be available
> > for guest use in the tdx_guest_keyid_start and tdx_nr_guest_keyids
> > variables.
> >
> > Use this range of HKIDs reserved for guest use with the kernel's IDA
> > allocator library helper to create a mini TDX HKID allocator that can be
> > called when setting up a TD. This way it can have an exclusive HKID, as is
> > required. This allocator will be used in future changes.
>
> This is basically what Dave was asking for, isn't it?

This patch has the allocator in KVM code, and the keyid ranges exported from
arch/x86. Per the discussion with Dave we will export the allocator functions
and keep the keyid ranges in arch/x86 code.