On 17.08.2021 12:30, Andrew Cooper wrote: > On 17/08/2021 09:54, Jan Beulich wrote: >> On 16.08.2021 21:25, Andrew Cooper wrote: >>> On 16/08/2021 16:29, Jan Beulich wrote: >>>> and an apparently wrong comment stating >>>> that not only v_end but also v_start would be superpage aligned >>> Which comment? The only one I see about 4M has nothing to do with >>> superpages. >> The one immediately ahead of the related variable declarations: >> >> /* >> * This fully describes the memory layout of the initial domain. All >> * *_start address are page-aligned, except v_start (and v_end) which are >> * superpage-aligned. >> */ >> >> I see nothing forcing v_start to be superpage-aligned, while I >> do suspect that the "calculation" of the number of page tables >> will be wrong when it isn't. > > This is an XTF test booting as dom0 > > (d2) (XEN) *** Building a PV Dom0 *** > (d2) (XEN) ELF: phdr: paddr=0x100000 memsz=0x12000 > (d2) (XEN) ELF: memory: 0x100000 -> 0x112000 > (d2) (XEN) ELF: note: GUEST_OS = "XTF" > (d2) (XEN) ELF: note: GUEST_VERSION = "0" > (d2) (XEN) ELF: note: LOADER = "generic" > (d2) (XEN) ELF: note: HYPERCALL_PAGE = 0x106000 > (d2) (XEN) ELF: note: XEN_VERSION = "xen-3.0" > (d2) (XEN) ELF: note: FEATURES = "!writable_page_tables|pae_pgdir_above_4gb" > (d2) (XEN) ELF: note: PAE_MODE = "yes" > (d2) (XEN) ELF: using notes from SHT_NOTE section > (d2) (XEN) ELF: VIRT_BASE unset, using 0 > (d2) (XEN) ELF_PADDR_OFFSET unset, using 0 > (d2) (XEN) ELF: addresses: > (d2) (XEN) virt_base = 0x0 > (d2) (XEN) elf_paddr_offset = 0x0 > (d2) (XEN) virt_offset = 0x0 > (d2) (XEN) virt_kstart = 0x100000 > (d2) (XEN) virt_kend = 0x112000 > (d2) (XEN) virt_entry = 0x100000 > (d2) (XEN) p2m_base = 0xffffffffffffffff > (d2) (XEN) Xen kernel: 64-bit, lsb, compat32 > (d2) (XEN) Dom0 kernel: 64-bit, PAE, lsb, paddr 0x100000 -> 0x112000 > (d2) (XEN) PHYSICAL MEMORY ARRANGEMENT: > (d2) (XEN) Dom0 alloc.: 000000003e800000->000000003ec00000 (240731 > pages to be allocated) > (d2) (XEN) VIRTUAL MEMORY ARRANGEMENT: > (d2) (XEN) Loaded kernel: 0000000000100000->0000000000112000 > (d2) (XEN) Init. ramdisk: 0000000000112000->0000000000112000 > (d2) (XEN) Phys-Mach map: 0000000000112000->00000000002ea2d8 > (d2) (XEN) Start info: 00000000002eb000->00000000002eb4b8 > (d2) (XEN) Xenstore ring: 0000000000000000->0000000000000000 > (d2) (XEN) Console ring: 0000000000000000->0000000000000000 > (d2) (XEN) Page tables: 00000000002ec000->00000000002f1000 > (d2) (XEN) Boot stack: 00000000002f1000->00000000002f2000 > (d2) (XEN) TOTAL: 0000000000000000->0000000000400000 > (d2) (XEN) ENTRY ADDRESS: 0000000000100000 > > It would appear that v_start comes directly and unmodified from the > VIRT_BASE ELF note. > > Other observations: The ramdisk start/end aren't zero despite one being > absent, and the M2P and start info ends aren't aligned.
I've already dealt with this ramdisk aspect in the v2 patch altering the printing. For *_end there's nothing wrong to be misaligned (as per the comment in question) - only v_end has a statement. Jan
