Thanks. 在 2022/7/2 1:24, Catalin Marinas 写道:
On Thu, Jun 30, 2022 at 06:50:22PM +0800, Guanghui Feng wrote:+static void init_pmd_remap(pud_t *pudp, unsigned long addr, unsigned long end, + phys_addr_t phys, pgprot_t prot, + phys_addr_t (*pgtable_alloc)(int), int flags) +{ + unsigned long next; + pmd_t *pmdp; + phys_addr_t map_offset; + pmdval_t pmdval; + + pmdp = pmd_offset(pudp, addr); + do { + next = pmd_addr_end(addr, end); + + if (!pmd_none(*pmdp) && pmd_sect(*pmdp)) { + phys_addr_t pte_phys = pgtable_alloc(PAGE_SHIFT); + pmd_clear(pmdp); + pmdval = PMD_TYPE_TABLE | PMD_TABLE_UXN; + if (flags & NO_EXEC_MAPPINGS) + pmdval |= PMD_TABLE_PXN; + __pmd_populate(pmdp, pte_phys, pmdval); + flush_tlb_kernel_range(addr, addr + PAGE_SIZE);This doesn't follow the architecture requirements for "break before make" when changing live page tables. While it may work, it risks triggering a TLB conflict abort. The correct sequence normally is: pmd_clear(); flush_tlb_kernel_range(); __pmd_populate(); However, do we have any guarantees that the kernel doesn't access the pmd range being unmapped temporarily? The page table itself might live in one of these sections, so set_pmd() etc. can get a translation fault.
Thanks. I'll follow this. I'll resend the path as soon as possible.
