4.19-stable review patch. If anyone has any objections, please let me know.
------------------
From: Steve Wahl steve.wahl@hpe.com
commit d794734c9bbfe22f86686dc2909c25f5ffe1a572 upstream.
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. On UV systems, this ends up including regions that will cause hardware to halt the system if accessed (these are marked "reserved" by BIOS). Even processor speculation into these regions is enough to trigger the system halt.
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.
[ dhansen: fix up comment formatting, simplifty changelog ]
Signed-off-by: Steve Wahl steve.wahl@hpe.com Signed-off-by: Dave Hansen dave.hansen@linux.intel.com Cc: stable@vger.kernel.org Link: https://lore.kernel.org/all/20240126164841.170866-1-steve.wahl%40hpe.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/mm/ident_map.c | 23 ++++++++++++++++++----- 1 file changed, 18 insertions(+), 5 deletions(-)
--- 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_map 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_large(*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;