On Wed, Nov 20, 2024 at 06:24:56PM +0100, Valentin Schneider wrote: > > Oh gawd, just having looked at xen_write_cr3() this might not be > > entirely trivial to mark noinstr :/ > > ... I hadn't even seen that. > > AIUI the CR3 RMW is not "enough" if we have PGE enabled, because then > global pages aren't flushed. > > The question becomes: what is held in global pages and do we care about > that when it comes to vmalloc()? I'm starting to think no, but this is x86, > I don't know what surprises are waiting for me. > > I see e.g. ds_clear_cea() clears PTEs that can have the _PAGE_GLOBAL flag, > and it correctly uses the non-deferrable flush_tlb_kernel_range(). I always forget what we use global pages for, dhansen might know, but let me try and have a look. I *think* we only have GLOBAL on kernel text, and that only sometimes.
