On 21.11.2024 16:56, Roger Pau Monné wrote: > On Thu, Nov 21, 2024 at 12:12:18PM +0100, Roger Pau Monne wrote: >> The allocation of the paging structures in the per-domain area for mapping >> the >> guest GDT and LDT can be limited to the maximum number of vCPUs the guest can >> have. The maximum number of vCPUs is available at domain creation since >> commit >> 4737fa52ce86. >> >> Limiting to the actual number of vCPUs avoids wasting memory for paging >> structures that will never be used. Current logic unconditionally uses 513 >> pages, one page for the L3, plus 512 L1 pages. > > This is not true, I was confused with the logic in > create_perdomain_mapping(). When create_perdomain_mapping() is called > with pl1tab == NULL and ppg == NULL it just allocates the L2, but not > the L1 tables. > > So the purpose of the create_perdomain_mapping(d, GDT_LDT_VIRT_START, > ...) in pv_domain_initialise() is even more dubious now - as it just > allocates a page to use as L2. I'm tempted to just remove it if you > agree, since I don't consider this useful. The allocation will > already be done at vCPU initialization.
If it's done implicitly there, removing is likely fine. It feels like it may have been necessary to do this explicitly earlier on. Jan
