Re: [PATCH v9 09/11] x86/virt/tdx: Enable Dynamic PAMT

On Mon, 2026-08-10 at 06:57 -0700, Dave Hansen wrote:
> On 8/5/26 19:08, Rick Edgecombe wrote:
> > The TDX module exposes whether Dynamic PAMT is supported via a bit in the
> > 'features0' metadata. Unfortunately, the TDX module exposes the feature as
> > supported even when it does not support using it with the number of keyids
> > currently configured in the BIOS.
> 
> What's the connection between DPAMT and the number of keyids? They seem
> orthogonal to me.

AFAIU, TDX module has, or had(?), some page tables like structures internally
for PAMT. Not just the 4KB level that we are handling. If the physical address
width is too large, it exceeds what the N-levels of these tables can handle. So
if there are enough keyids, then your physical address width can be small
enough. Although I'm not sure of the details of whether those limits are really
needed.