Balbir Singh <bsinghar...@gmail.com> writes:
>> +
.......
>> +/*
>> + * map_kernel_page currently only called by __ioremap
>> + * map_kernel_page adds an entry to the ioremap page table
>> + * and adds an entry to the HPT, possibly bolting it
>> + */
>> +int map_kernel_page(unsigned long ea, unsigned long pa, unsigned long flags)
>> +{
>> + pgd_t *pgdp;
>> + pud_t *pudp;
>> + pmd_t *pmdp;
>> + pte_t *ptep;
>> +
>> + if (slab_is_available()) {
>> + pgdp = pgd_offset_k(ea);
>> + pudp = pud_alloc(&init_mm, pgdp, ea);
>> + if (!pudp)
>> + return -ENOMEM;
>> + pmdp = pmd_alloc(&init_mm, pudp, ea);
>> + if (!pmdp)
>> + return -ENOMEM;
>> + ptep = pte_alloc_kernel(pmdp, ea);
>> + if (!ptep)
>> + return -ENOMEM;
>> + set_pte_at(&init_mm, ea, ptep, pfn_pte(pa >> PAGE_SHIFT,
>> + __pgprot(flags)));
>> + } else {
>> + /*
>> + * If the mm subsystem is not fully up, we cannot create a
>> + * linux page table entry for this mapping. Simply bolt an
>> + * entry in the hardware page table.
>> + *
>> + */
>> + if (htab_bolt_mapping(ea, ea + PAGE_SIZE, pa, flags,
>> + mmu_io_psize, mmu_kernel_ssize)) {
>> + printk(KERN_ERR "Failed to do bolted mapping IO "
>> + "memory at %016lx !\n", pa);
>> + return -ENOMEM;
>
> What happens when we do unmap this? I know this code has been around for a
> while
> so its not new
you mean iounmap ? it do call vunmap, which look for a linux page table
entry. If it is a bolt_mapping entry as above, we will not have a linux
page table entry and that unmap will not relaly remove the mapping.
>
>> + }
>> + }
>> +
>> + smp_wmb();
>> + return 0;
>> +}
-aneesh
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