x86/virt/tdx: Enable Dynamic PAMT

The Physical Address Metadata Table (PAMT) holds TDX metadata for
physical memory and must be allocated by the kernel during TDX module
initialization. Dynamic PAMT (DPAMT) is a TDX module feature that can
reduce this memory use by allocating part of the PAMT dynamically.

DPAMT's memory savings are significant enough to make it a good default
configuration. So turn it on whenever the TDX module reports support.

There is a TDX module bug where on unusual BIOS keyid configurations, the
TDX module reports DPAMT as supported even when it can't handle it. Expect
this not to be an issue in practice and don't attempt to work around it on
the kernel side.

The feature increases the kernel size by 2KB (when TDX is configured in the
build).

Based on a patch originally by Kiryl Shutsemau.

Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Tony Lindgren <tony.lindgren@linux.intel.com>
Reviewed-by: Vishal Annapurve <vannapurve@google.com>
Acked-by: Sohil Mehta <sohil.mehta@intel.com>
Tested-by: Hongyu Ning <hongyu.ning@linux.intel.com>
Link: https://patch.msgid.link/20260904215841.303070-10-rick.p.edgecombe@intel.com

0 files changed, 0 insertions, 0 deletions