On Tue, May 13, 2025 at 6:12 PM Huang, Kai <kai.huang@xxxxxxxxx> wrote: > > > > On 3/05/2025 1:08 am, Kirill A. Shutemov wrote: > > The PAMT memory holds metadata for TDX-protected memory. With Dynamic > > PAMT, PAMT_4K is allocated on demand. The kernel supplies the TDX module > > with a few pages that cover 2M of host physical memory. > > > > PAMT memory can be reclaimed when the last user is gone. It can happen > > in a few code paths: > > > > - On TDH.PHYMEM.PAGE.RECLAIM in tdx_reclaim_td_control_pages() and > > tdx_reclaim_page(). > > > > - On TDH.MEM.PAGE.REMOVE in tdx_sept_drop_private_spte(). > > > > - In tdx_sept_zap_private_spte() for pages that were in the queue to be > > added with TDH.MEM.PAGE.ADD, but it never happened due to an error. > > > > Add tdx_pamt_put() in these code paths. > > IMHO, instead of explicitly hooking tdx_pamt_put() to various places, we > should just do tdx_free_page() for the pages that were allocated by > tdx_alloc_page() (i.e., control pages, SEPT pages). > > That means, IMHO, we should do PAMT allocation/free when we actually > *allocate* and *free* the target TDX private page(s). I.e., we should: I think it's important to ensure that PAMT pages are *only* allocated for a 2M range if it's getting mapped in EPT at 4K granularity. Physical memory allocation order can be different from the EPT mapping granularity.
