[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] x86/mm: Skip the hypervisor range when walking PGD
On 11/05/2015 05:31 PM, H. Peter Anvin wrote: On 11/05/15 10:56, Boris Ostrovsky wrote:The range between 0xffff800000000000 and 0xffff87ffffffffff is reserved for hypervisor and therefore we should not try to follow PGD's indexes corresponding to those addresses. While this has alsways been a problem, with commit e1a58320a38d ("x86/mm: Warn on W^X mappings") ptdump_walk_pgd_level_core() can now be called during boot, causing a PV Xen guest to crash. Reported-by: Sander Eikelenboom <linux@xxxxxxxxxxxxxx> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> --- arch/x86/mm/dump_pagetables.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c index 1bf417e..756c921 100644 --- a/arch/x86/mm/dump_pagetables.c +++ b/arch/x86/mm/dump_pagetables.c @@ -362,8 +362,13 @@ static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd, bool checkwx) { #ifdef CONFIG_X86_64 +/* ffff800000000000 - ffff87ffffffffff is reserved for hypervisor */ +#define is_hypervisor_range(idx) (paravirt_enabled() && \ + (((idx) >= pgd_index(__PAGE_OFFSET) - 16) && \ + ((idx) < pgd_index(__PAGE_OFFSET)))) pgd_t *start = (pgd_t *) &init_level4_pgt; #else +#define is_hypervisor_range(idx) 0 pgd_t *start = swapper_pg_dir; #endif pgprotval_t prot; @@ -381,7 +386,7 @@ static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,for (i = 0; i < PTRS_PER_PGD; i++) {st.current_address = normalize_addr(i * PGD_LEVEL_MULT); - if (!pgd_none(*start)) { + if (!pgd_none(*start) && !is_hypervisor_range(i)) { if (pgd_large(*start) || !pgd_present(*start)) { prot = pgd_flags(*start); note_page(m, &st, __pgprot(prot), 1);Maybe we could use the max_lines field in the address_markers[] array? We really shouldn't be mapping anything in the hypervisor space even on native. You mean overload max_lines with a value indicating that the range needs to be skipped? That would require checking the range on each loop iteration since we update st.marker *after* we've walked a particular index. (And I think it would need to be done on each level to be generic). I could just drop paravirt_enabled() in is_hypervisor_range() but you are thinking about avoiding the macro altogether, right? (I do need to add hypervisor range to address_markers[]) -boris _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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