On Wed, 2022-08-03 at 07:22 -0700, Dave Hansen wrote: > On 8/2/22 18:30, Kai Huang wrote: > > On Fri, 2022-07-08 at 11:34 +1200, Kai Huang wrote: > > > > Why not just entirely remove the lower 1MB from the memblock structure > > > > on TDX systems? Do something equivalent to adding this on the kernel > > > > command line: > > > > > > > > memmap=1M$0x0 > > > I will explore this option. Thanks! > > Hi Dave, > > > > After investigating and testing, we cannot simply remove first 1MB from e820 > > table which is similar to what 'memmap=1M$0x0' does, as the kernel needs low > > memory as trampoline to bring up all APs. > > OK, so don't remove it, but reserve it so that the trampoline code can > use it. It's already reserved in the existing reserve_real_mode(). What we need is to *remove* the first 1MB from memblock.memory, so that the for_each_mem_pfn_range() will just not get any memory below 1MB. Otherwise we need to explicitly skip the first 1MB in TDX code like what I did in this series. -- Thanks, -Kai
