On 20/12/17 01:22, Thomas Gleixner wrote: > On Tue, 19 Dec 2017, Thomas Gleixner wrote: >> On Tue, 19 Dec 2017, Ingo Molnar wrote: >> We don't run out of space, but the 0-day robot triggered a nasty issue. >> >> The fixmap bottom address, which contains the early_ioremap fixmap area, is: >> >> vaddr_bt = FIXADDR_TOP - FIX_BTMAP_BEGIN * PAGE_SIZE >> >> If that address is lower than: >> >> vaddr_end = __START_KERNEL_map + KERNEL_IMAGE_SIZE; >> >> then cleanup_highmap() will happily 0 out the PMD entry for the PTE page of >> FIX_BTMAP. That entry was set up earlier in early_ioremap_init(). >> >> As a consequence the first call to __early_set_fixmap() which tries to >> install a PTE for early_ioremap() will crash and burn. >> >> Below is a nasty hack which fixes the problem. Ideally we get all of this >> cpu_entry_stuff out of the fixmap. I'll look into that later, but for now >> the patch 'fixes' the issue. > > I had a stab on moving the cpu_entry_area to some other place. > > The patch below works, but: > > - it breaks i386 build because I have not yet found a way to place the > CPU_ENTRY_AREA_BASE without creating include recursion hell > > - it probably does not work on XEN_PV, but I'm too tired now to figure > that out.
The attached patch lets the system come up as XEN_PV. Juergen
diff --git a/arch/x86/entry/vsyscall/vsyscall_64.c b/arch/x86/entry/vsyscall/vsyscall_64.c index e4a6fe8354f0..577fa8adb785 100644 --- a/arch/x86/entry/vsyscall/vsyscall_64.c +++ b/arch/x86/entry/vsyscall/vsyscall_64.c @@ -37,6 +37,7 @@ #include <asm/unistd.h> #include <asm/fixmap.h> #include <asm/traps.h> +#include <asm/paravirt.h> #define CREATE_TRACE_POINTS #include "vsyscall_trace.h" @@ -351,15 +352,15 @@ void __init set_vsyscall_pgtable_user_bits(pgd_t *root) pmd_t *pmd; pgd = pgd_offset_pgd(root, VSYSCALL_ADDR); - pgd->pgd |= _PAGE_USER; + set_pgd(pgd, __pgd(pgd_val(*pgd) | _PAGE_USER)); p4d = p4d_offset(pgd, VSYSCALL_ADDR); #if CONFIG_PGTABLE_LEVELS >= 5 p4d->p4d |= _PAGE_USER; #endif pud = pud_offset(p4d, VSYSCALL_ADDR); - pud->pud |= _PAGE_USER; + set_pud(pud, __pud(pud_val(*pud) | _PAGE_USER)); pmd = pmd_offset(pud, VSYSCALL_ADDR); - pmd->pmd |= _PAGE_USER; + set_pmd(pmd, __pmd(pmd_val(*pmd) | _PAGE_USER)); } void __init map_vsyscall(void)
