On 17/09/18 10:39, 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 | 7 +++++-- > 5 files changed, 32 insertions(+), 7 deletions(-) > > diff --git a/arch/x86/include/asm/fixmap.h b/arch/x86/include/asm/fixmap.h > index e203169..ffaa0fa 100644 > --- a/arch/x86/include/asm/fixmap.h > +++ b/arch/x86/include/asm/fixmap.h > @@ -14,6 +14,9 @@ > #ifndef _ASM_X86_FIXMAP_H > #define _ASM_X86_FIXMAP_H > > +/* Put here to be accessble for assembly code like head_64.S */ > +#define FIXMAP_PMD_NUM 2 > + > #ifndef __ASSEMBLY__ > #include <linux/kernel.h> > #include <asm/acpi.h> > diff --git a/arch/x86/include/asm/pgtable_64.h > b/arch/x86/include/asm/pgtable_64.h > index ce2b590..9c85b54 100644 > --- a/arch/x86/include/asm/pgtable_64.h > +++ b/arch/x86/include/asm/pgtable_64.h > @@ -14,6 +14,7 @@ > #include <asm/processor.h> > #include <linux/bitops.h> > #include <linux/threads.h> > +#include <asm/fixmap.h> > > extern p4d_t level4_kernel_pgt[512]; > extern p4d_t level4_ident_pgt[512]; > @@ -22,7 +23,7 @@ extern pud_t level3_ident_pgt[512]; > extern pmd_t level2_kernel_pgt[512]; > extern pmd_t level2_fixmap_pgt[512]; > extern pmd_t level2_ident_pgt[512]; > -extern pte_t level1_fixmap_pgt[512]; > +extern pte_t level1_fixmap_pgt[512 * FIXMAP_PMD_NUM]; > extern pgd_t init_top_pgt[]; > > #define swapper_pg_dir init_top_pgt > diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S > index 15ebc2f..a3618cf 100644 > --- a/arch/x86/kernel/head_64.S > +++ b/arch/x86/kernel/head_64.S > @@ -24,6 +24,7 @@ > #include "../entry/calling.h" > #include <asm/export.h> > #include <asm/nospec-branch.h> > +#include <asm/fixmap.h> > > #ifdef CONFIG_PARAVIRT > #include <asm/asm-offsets.h> > @@ -445,13 +446,20 @@ NEXT_PAGE(level2_kernel_pgt) > KERNEL_IMAGE_SIZE/PMD_SIZE) > > NEXT_PAGE(level2_fixmap_pgt) > - .fill 506,8,0 > - .quad level1_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC > - /* 8MB reserved for vsyscalls + a 2MB hole = 4 + 1 entries */ > - .fill 5,8,0 > + .fill (512 - 4 - FIXMAP_PMD_NUM),8,0 > + pgtno = 0 > + .rept (FIXMAP_PMD_NUM) > + .quad level1_fixmap_pgt + (pgtno << PAGE_SHIFT) - __START_KERNEL_map \ > + + _PAGE_TABLE_NOENC; > + pgtno = pgtno + 1 > + .endr > + /* 6 MB reserved space + a 2MB hole */ > + .fill 4,8,0 > > NEXT_PAGE(level1_fixmap_pgt) > + .rept (FIXMAP_PMD_NUM) > .fill 512,8,0 > + .endr > > #undef PMDS > > diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c > index ae39455..a4052b1 100644 > --- a/arch/x86/mm/pgtable.c > +++ b/arch/x86/mm/pgtable.c > @@ -637,6 +637,16 @@ void __native_set_fixmap(enum fixed_addresses idx, pte_t > pte) > { > unsigned long address = __fix_to_virt(idx); > > +#ifdef CONFIG_X86_64 > + /* > + * In arch/x86/kernel/head_64.S, the static page table has > + * been setup for fixmap. Add a sanity compiling check > + * whether fixmap space has exceeded the capacity. > + */ > + BUILD_BUG_ON(__end_of_permanent_fixed_addresses > + > (FIXMAP_PMD_NUM * PTRS_PER_PMD)); > +#endif > + > if (idx >= __end_of_fixed_addresses) { > BUG(); > return; > diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c > index 2fe5c9b..74c4e17 100644 > --- a/arch/x86/xen/mmu_pv.c > +++ b/arch/x86/xen/mmu_pv.c > @@ -1907,7 +1907,7 @@ void __init xen_setup_kernel_pagetable(pgd_t *pgd, > unsigned long max_pfn) > /* L3_k[511] -> level2_fixmap_pgt */ > convert_pfn_mfn(level3_kernel_pgt); > > - /* L3_k[511][506] -> level1_fixmap_pgt */ > + /* L3_k[507, 508 - FIXMAP_PMD_NUM] -> level1_fixmap_pgt */
You messed up the comment. The [511] must not be dropped. I would swap the "508 - FIXMAP_PMD_NUM" and "507" in order to start with the lower index, and replace "," by "...": + /* L3_k[511][508-FIXMAP_PMD_NUM ... 507] -> level1_fixmap_pgt */ With that corrected you can have my: Reviewed-by: Juergen Gross <[email protected]> (Xen parts) Juergen
