On September 2, 2021 3:18 PM, Gerd Hoffmann wrote: > Hi, > > > > Sure. And I think we should add proper 5-level paging support to > > > the current ovmf implementation instead of adding hacks to the tdx code. > > My understanding is that we should first add 5-level paging support in > OVMF, right? > > Well, the page table setup should be in common code not tdx code as 5-level > paging isn't something tdx-specific. Agree. > > I'd suggest to add this to OvmfPkg/ResetVector/Ia32/PageTables64.asm. > Reserve one more page, setup the tables for 5-level paging by inserting a > level 5 page directory. In the current patch a page (defined by PcdOvmfSecGhcbPageTableBase) reserved in MEMFD is used as the 5-level page directory. Now One new page will be reserved in MEMFD to hold the level 5 page directory. Like below: 0x00C000|0x001000 gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBackupBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBackupSize
+0x00D000|0x001000 +gUefiOvmfPkgTokenSpaceGuid.PcdOvmfPml5Base|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfPml5Size > > When using 5-level paging let cr3 point to the first page (level 5 pagedir), > when using 4-level paging let cr3 point to the second page (level 4 pagedir). Yes. CPUID.(EAX=07H, ECX=0):ECX[bit 16] will be used to check if 5-level paging is supported. > > Can be part of this patch series, just make it a separate patch for easier > review. Sure. > > Whenever we should enable 5-level paging even in non-tdx mode or use 5- > level paging only with tdx is a separate question. We can continue to use 4- > level paging in non-tdx mode for now and discuss that later. Agree. > > I'm not sure which implications this would have for booting older kernels, > when handing over control to a OS kernel without 5-level paging support but > 5-level paging enabled (non-issue for tdx as this requires a new tdx-aware > guest kernel anyway ...). Thanks! Min -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#80148): https://edk2.groups.io/g/devel/message/80148 Mute This Topic: https://groups.io/mt/85242569/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
