On 17/09/18 09:34, Feng Tang wrote: > We met a kernel panic when enabling earlycon, which is due to > the fixmap address of earlycon is not statically setup. > > Currently the static fixmap setup in head_64.S only covers 2M > virtual address space, while it acutually could be in 4M space > with different kernel configurations. > > So increase the static space to 4M for now by defining FIXMAP_PMD_NUM > to 2, and add a build time check for future possible overflow so that > the macro could be increased accordingly. > > Suggested-by: Thomas Gleixner <[email protected]> > Signed-off-by: Feng Tang <[email protected]> > --- > arch/x86/include/asm/fixmap.h | 3 +++ > arch/x86/include/asm/pgtable_64.h | 3 ++- > arch/x86/kernel/head_64.S | 16 ++++++++++++---- > arch/x86/mm/pgtable.c | 10 ++++++++++ > arch/x86/xen/mmu_pv.c | 4 +++- > 5 files changed, 30 insertions(+), 6 deletions(-) >
... > diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c > index 2fe5c9b..19077f9 100644 > --- a/arch/x86/xen/mmu_pv.c > +++ b/arch/x86/xen/mmu_pv.c > @@ -1952,7 +1952,9 @@ void __init xen_setup_kernel_pagetable(pgd_t *pgd, > unsigned long max_pfn) > set_page_prot(level2_ident_pgt, PAGE_KERNEL_RO); > set_page_prot(level2_kernel_pgt, PAGE_KERNEL_RO); > set_page_prot(level2_fixmap_pgt, PAGE_KERNEL_RO); > - set_page_prot(level1_fixmap_pgt, PAGE_KERNEL_RO); > + > + for (i = 0; i < FIXMAP_PMD_NUM; i++) > + set_page_prot(level1_fixmap_pgt + i * 512, PAGE_KERNEL_RO); Please use PTRS_PER_PTE instead of the literal 512. Some lines further up level1_fixmap_pgt is mentioned in a comment. Please update that, too: - /* L3_k[511][506] -> level1_fixmap_pgt */ + /* L3_k[511][506, ...] -> level1_fixmap_pgt */ Juergen
