Gentle ping: Can someone please take the time to review this patch? This patch was previously approved by Dave Hansen, but was reverted. Full series (of 2 + cover leter) viewable at: https://lore.kernel.org/all/20240717213121.3064030-1-steve.wahl@xxxxxxx/ Thanks. --> Steve Wahl, HPE On Wed, Jul 17, 2024 at 04:31:21PM -0500, Steve Wahl wrote: > When ident_pud_init() uses only gbpages to create identity maps, large > ranges of addresses not actually requested can be included in the > resulting table; a 4K request will map a full GB. This can include a > lot of extra address space past that requested, including areas marked > reserved by the BIOS. That allows processor speculation into reserved > regions, that on UV systems can cause system halts. > > Only use gbpages when map creation requests include the full GB page > of space. Fall back to using smaller 2M pages when only portions of a > GB page are included in the request. > > No attempt is made to coalesce mapping requests. If a request requires > a map entry at the 2M (pmd) level, subsequent mapping requests within > the same 1G region will also be at the pmd level, even if adjacent or > overlapping such requests could have been combined to map a full > gbpage. Existing usage starts with larger regions and then adds > smaller regions, so this should not have any great consequence. > > Signed-off-by: Steve Wahl <steve.wahl@xxxxxxx> > Tested-by: Pavin Joseph <me@xxxxxxxxxxxxxxx> > Tested-by: Sarah Brofeldt <srhb@xxxxxx> > Tested-by: Eric Hagberg <ehagberg@xxxxxxxxx> > --- > arch/x86/mm/ident_map.c | 23 ++++++++++++++++++----- > 1 file changed, 18 insertions(+), 5 deletions(-) > > diff --git a/arch/x86/mm/ident_map.c b/arch/x86/mm/ident_map.c > index 968d7005f4a7..a204a332c71f 100644 > --- a/arch/x86/mm/ident_map.c > +++ b/arch/x86/mm/ident_map.c > @@ -26,18 +26,31 @@ static int ident_pud_init(struct x86_mapping_info *info, pud_t *pud_page, > for (; addr < end; addr = next) { > pud_t *pud = pud_page + pud_index(addr); > pmd_t *pmd; > + bool use_gbpage; > > next = (addr & PUD_MASK) + PUD_SIZE; > if (next > end) > next = end; > > - if (info->direct_gbpages) { > - pud_t pudval; > + /* if this is already a gbpage, this portion is already mapped */ > + if (pud_leaf(*pud)) > + continue; > + > + /* Is using a gbpage allowed? */ > + use_gbpage = info->direct_gbpages; > > - if (pud_present(*pud)) > - continue; > + /* Don't use gbpage if it maps more than the requested region. */ > + /* at the begining: */ > + use_gbpage &= ((addr & ~PUD_MASK) == 0); > + /* ... or at the end: */ > + use_gbpage &= ((next & ~PUD_MASK) == 0); > + > + /* Never overwrite existing mappings */ > + use_gbpage &= !pud_present(*pud); > + > + if (use_gbpage) { > + pud_t pudval; > > - addr &= PUD_MASK; > pudval = __pud((addr - info->offset) | info->page_flag); > set_pud(pud, pudval); > continue; > -- > 2.26.2 > -- Steve Wahl, Hewlett Packard Enterprise
