/*
* We can receive a page fault from a migrating PTE at any time.
* Handle it by just waiting until the fault resolves.
*
* It's also possible to get a migrating kernel PTE that resolves
* itself during the downcall from hypervisor to Linux. We just check
* here to see if the PTE seems valid, and if so we retry it.
*
* NOTE! We MUST NOT take any locks for this case. We may be in an
* interrupt or a critical region, and must do as little as possible.
* Similarly, we can't use atomic ops here, since we may be handling a
* fault caused by an atomic op access.
*
* If we find a migrating PTE while we're in an NMI context, and we're
* at a PC that has a registered exception handler, we don't wait,
* since this thread may (e.g.) have been interrupted while migrating
* its own stack, which would then cause us to self-deadlock.
*/
static int handle_migrating_pte(pgd_t *pgd, int fault_num,
unsigned long address, unsigned long pc,
int is_kernel_mode, int write)
{
pud_t *pud;
pmd_t *pmd;
pte_t *pte;
pte_t pteval;
if (pgd_addr_invalid(address))
return 0;
pgd += pgd_index(address);
pud = pud_offset(pgd, address);
if (!pud || !pud_present(*pud))
return 0;
pmd = pmd_offset(pud, address);
if (!pmd || !pmd_present(*pmd))
return 0;
pte = pmd_huge_page(*pmd) ? ((pte_t *)pmd) :
pte_offset_kernel(pmd, address);
pteval = *pte;
if (pte_migrating(pteval)) {
if (in_nmi() && search_exception_tables(pc))
return 0;
wait_for_migration(pte);
return 1;
}
if (!is_kernel_mode || !pte_present(pteval))
return 0;
if (fault_num == INT_ITLB_MISS) {
if (pte_exec(pteval))
return 1;
} else if (write) {
if (pte_write(pteval))
return 1;
} else {
if (pte_read(pteval))
return 1;
}
return 0;
}
pte_t *virt_to_pte(struct mm_struct* mm, unsigned long addr)
{
pgd_t *pgd;
pud_t *pud;
pmd_t *pmd;
if (pgd_addr_invalid(addr))
return NULL;
pgd = mm ? pgd_offset(mm, addr) : swapper_pg_dir + pgd_index(addr);
pud = pud_offset(pgd, addr);
if (!pud_present(*pud))
return NULL;
pmd = pmd_offset(pud, addr);
if (pmd_huge_page(*pmd))
return (pte_t *)pmd;
if (!pmd_present(*pmd))
return NULL;
return pte_offset_kernel(pmd, addr);
}
