From: Vasily Gorbik Date: Fri, 28 Nov 2025 22:01:05 +0000 (+0100) Subject: s390/vmem: Support 2G page splitting for KASAN shadow freeing X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=6a35d02fec5a1e2ab6c0c94ccc5b0c57a580b098;p=thirdparty%2Fkernel%2Fstable.git s390/vmem: Support 2G page splitting for KASAN shadow freeing Export split_pud_page() so it can be used from the vmem code and teach modify_pud_table() to split PUD-sized mappings when only a subrange needs to be removed. If the range to be removed covers a full PUD-sized mapping, keep the existing behavior: clear the PUD entry and free the backing large page (for non-direct mappings). Otherwise, split the PUD-mapped page into PMD mappings and let the walker handle the smaller ranges. This is needed for KASAN early shadow removal support: memory hotplug freeing the KASAN early shadow is the only expected caller that will try to free 2G PUD-mapped regions of non-direct mappings. Signed-off-by: Vasily Gorbik Reviewed-by: Heiko Carstens Signed-off-by: Heiko Carstens --- diff --git a/arch/s390/include/asm/page.h b/arch/s390/include/asm/page.h index 9240a363c893..c1d63b613bf9 100644 --- a/arch/s390/include/asm/page.h +++ b/arch/s390/include/asm/page.h @@ -166,6 +166,8 @@ static inline int page_reset_referenced(unsigned long addr) return CC_TRANSFORM(cc); } +int split_pud_page(pud_t *pudp, unsigned long addr); + /* Bits int the storage key */ #define _PAGE_CHANGED 0x02 /* HW changed bit */ #define _PAGE_REFERENCED 0x04 /* HW referenced bit */ diff --git a/arch/s390/mm/pageattr.c b/arch/s390/mm/pageattr.c index 3042647c9dbf..d3ce04a4b248 100644 --- a/arch/s390/mm/pageattr.c +++ b/arch/s390/mm/pageattr.c @@ -204,7 +204,7 @@ static int walk_pmd_level(pud_t *pudp, unsigned long addr, unsigned long end, return rc; } -static int split_pud_page(pud_t *pudp, unsigned long addr) +int split_pud_page(pud_t *pudp, unsigned long addr) { unsigned long pmd_addr, prot; pmd_t *pm_dir, *pmdp; diff --git a/arch/s390/mm/vmem.c b/arch/s390/mm/vmem.c index d96587b84e81..faed09531499 100644 --- a/arch/s390/mm/vmem.c +++ b/arch/s390/mm/vmem.c @@ -330,10 +330,14 @@ static int modify_pud_table(p4d_t *p4d, unsigned long addr, unsigned long end, if (pud_leaf(*pud)) { if (IS_ALIGNED(addr, PUD_SIZE) && IS_ALIGNED(next, PUD_SIZE)) { + if (!direct) + vmem_free_pages(pud_deref(*pud), get_order(PUD_SIZE), altmap); pud_clear(pud); pages++; + continue; + } else { + split_pud_page(pud, addr & PUD_MASK); } - continue; } } else if (pud_none(*pud)) { if (IS_ALIGNED(addr, PUD_SIZE) &&