[S390] Virtual memmap for s390.

Virtual memmap support for s390. Inspired by the ia64 implementation.

Unlike ia64 we need a mechanism which allows us to dynamically attach
shared memory regions.
These memory regions are accessed via the dcss device driver. dcss
implements the 'direct_access' operation, which requires struct pages
for every single shared page.
Therefore this implementation provides an interface to attach/detach
shared memory:

int add_shared_memory(unsigned long start, unsigned long size);
int remove_shared_memory(unsigned long start, unsigned long size);

The purpose of the add_shared_memory function is to add the given
memory range to the 1:1 mapping and to make sure that the
corresponding range in the vmemmap is backed with physical pages.
It also initialises the new struct pages.

remove_shared_memory in turn only invalidates the page table
entries in the 1:1 mapping. The page tables and the memory used for
struct pages in the vmemmap are currently not freed. They will be
reused when the next segment will be attached.
Given that the maximum size of a shared memory region is 2GB and
in addition all regions must reside below 2GB this is not too much of
a restriction, but there is room for improvement.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 41 insertions, 122 deletions

diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index e1881c31b1cb..5ea12a573cad 100644
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c
@@ -69,6 +69,8 @@ void show_mem(void)
         printk("Free swap:       %6ldkB\n", nr_swap_pages<<(PAGE_SHIFT-10));
         i = max_mapnr;
         while (i-- > 0) {
+                if (!pfn_valid(i))
+                        continue;
                 page = pfn_to_page(i);
                 total++;
                 if (PageReserved(page))
@@ -84,67 +86,53 @@ void show_mem(void)
         printk("%d pages swap cached\n",cached);
 }
 
+static void __init setup_ro_region(void)
+{
+        pgd_t *pgd;
+        pmd_t *pmd;
+        pte_t *pte;
+        pte_t new_pte;
+        unsigned long address, end;
+
+        address = ((unsigned long)&__start_rodata) & PAGE_MASK;
+        end = PFN_ALIGN((unsigned long)&__end_rodata);
+
+        for (; address < end; address += PAGE_SIZE) {
+                pgd = pgd_offset_k(address);
+                pmd = pmd_offset(pgd, address);
+                pte = pte_offset_kernel(pmd, address);
+                new_pte = mk_pte_phys(address, __pgprot(_PAGE_RO));
+                set_pte(pte, new_pte);
+        }
+}
+
 extern unsigned long __initdata zholes_size[];
+extern void vmem_map_init(void);
 /*
  * paging_init() sets up the page tables
  */
-
-#ifndef CONFIG_64BIT
 void __init paging_init(void)
 {
-        pgd_t * pg_dir;
-        pte_t * pg_table;
-        pte_t   pte;
-        int     i;
-        unsigned long tmp;
-        unsigned long pfn = 0;
-        unsigned long pgdir_k = (__pa(swapper_pg_dir) & PAGE_MASK) | _KERNSEG_TABLE;
-        static const int ssm_mask = 0x04000000L;
-        unsigned long ro_start_pfn, ro_end_pfn;
+        pgd_t *pg_dir;
+        int i;
+        unsigned long pgdir_k;
+        static const int ssm_mask = 0x04000000L;
         unsigned long zones_size[MAX_NR_ZONES];
+        unsigned long dma_pfn, high_pfn;
 
-        ro_start_pfn = PFN_DOWN((unsigned long)&__start_rodata);
-        ro_end_pfn = PFN_UP((unsigned long)&__end_rodata);
-
-        memset(zones_size, 0, sizeof(zones_size));
-        zones_size[ZONE_DMA] = max_low_pfn;
-        free_area_init_node(0, &contig_page_data, zones_size,
-                            __pa(PAGE_OFFSET) >> PAGE_SHIFT,
-                            zholes_size);
-
-        /* unmap whole virtual address space */
+        pg_dir = swapper_pg_dir;
         
-        pg_dir = swapper_pg_dir;
-
+#ifdef CONFIG_64BIT
+        pgdir_k = (__pa(swapper_pg_dir) & PAGE_MASK) | _KERN_REGION_TABLE;
         for (i = 0; i < PTRS_PER_PGD; i++)
-                pmd_clear((pmd_t *) pg_dir++);
-                
-        /*
-         * map whole physical memory to virtual memory (identity mapping) 
-         */
-
-        pg_dir = swapper_pg_dir;
-
-        while (pfn < max_low_pfn) {
-                /*
-                 * pg_table is physical at this point
-                 */
-                pg_table = (pte_t *) alloc_bootmem_pages(PAGE_SIZE);
-
-                pmd_populate_kernel(&init_mm, (pmd_t *) pg_dir, pg_table);
-                pg_dir++;
-
-                for (tmp = 0 ; tmp < PTRS_PER_PTE ; tmp++,pg_table++) {
-                        if (pfn >= ro_start_pfn && pfn < ro_end_pfn)
-                                pte = pfn_pte(pfn, __pgprot(_PAGE_RO));
-                        else
-                                pte = pfn_pte(pfn, PAGE_KERNEL);
-                        if (pfn >= max_low_pfn)
-                                pte_val(pte) = _PAGE_TYPE_EMPTY;
-                        set_pte(pg_table, pte);
-                        pfn++;
-                }
-        }
+                pgd_clear(pg_dir + i);
+#else
+        pgdir_k = (__pa(swapper_pg_dir) & PAGE_MASK) | _KERNSEG_TABLE;
+        for (i = 0; i < PTRS_PER_PGD; i++)
+                pmd_clear((pmd_t *)(pg_dir + i));
+#endif
+        vmem_map_init();
+        setup_ro_region();
 
         S390_lowcore.kernel_asce = pgdir_k;
 
@@ -154,31 +142,9 @@ void __init paging_init(void)
         __ctl_load(pgdir_k, 13, 13);
         __raw_local_irq_ssm(ssm_mask);
 
-        local_flush_tlb();
-}
-
-#else /* CONFIG_64BIT */
-
-void __init paging_init(void)
-{
-        pgd_t * pg_dir;
-        pmd_t * pm_dir;
-        pte_t * pt_dir;
-        pte_t   pte;
-        int     i,j,k;
-        unsigned long pfn = 0;
-        unsigned long pgdir_k = (__pa(swapper_pg_dir) & PAGE_MASK) |
-          _KERN_REGION_TABLE;
-        static const int ssm_mask = 0x04000000L;
-        unsigned long zones_size[MAX_NR_ZONES];
-        unsigned long dma_pfn, high_pfn;
-        unsigned long ro_start_pfn, ro_end_pfn;
-
         memset(zones_size, 0, sizeof(zones_size));
         dma_pfn = MAX_DMA_ADDRESS >> PAGE_SHIFT;
         high_pfn = max_low_pfn;
-        ro_start_pfn = PFN_DOWN((unsigned long)&__start_rodata);
-        ro_end_pfn = PFN_UP((unsigned long)&__end_rodata);
 
         if (dma_pfn > high_pfn)
                 zones_size[ZONE_DMA] = high_pfn;
@@ -190,56 +156,7 @@ void __init paging_init(void)
         /* Initialize mem_map[].  */
         free_area_init_node(0, &contig_page_data, zones_size,
                             __pa(PAGE_OFFSET) >> PAGE_SHIFT, zholes_size);
-
-        /*
-         * map whole physical memory to virtual memory (identity mapping) 
-         */
-
-        pg_dir = swapper_pg_dir;
-        
-        for (i = 0 ; i < PTRS_PER_PGD ; i++,pg_dir++) {
-        
-                if (pfn >= max_low_pfn) {
-                        pgd_clear(pg_dir);
-                        continue;
-                }          
-        
-                pm_dir = (pmd_t *) alloc_bootmem_pages(PAGE_SIZE * 4);
-                pgd_populate(&init_mm, pg_dir, pm_dir);
-
-                for (j = 0 ; j < PTRS_PER_PMD ; j++,pm_dir++) {
-                        if (pfn >= max_low_pfn) {
-                                pmd_clear(pm_dir);
-                                continue; 
-                        }          
-                        
-                        pt_dir = (pte_t *) alloc_bootmem_pages(PAGE_SIZE);
-                        pmd_populate_kernel(&init_mm, pm_dir, pt_dir);
-        
-                        for (k = 0 ; k < PTRS_PER_PTE ; k++,pt_dir++) {
-                                if (pfn >= ro_start_pfn && pfn < ro_end_pfn)
-                                        pte = pfn_pte(pfn, __pgprot(_PAGE_RO));
-                                else
-                                        pte = pfn_pte(pfn, PAGE_KERNEL);
-                                if (pfn >= max_low_pfn)
-                                        pte_val(pte) = _PAGE_TYPE_EMPTY;
-                                set_pte(pt_dir, pte);
-                                pfn++;
-                        }
-                }
-        }
-
-        S390_lowcore.kernel_asce = pgdir_k;
-
-        /* enable virtual mapping in kernel mode */
-        __ctl_load(pgdir_k, 1, 1);
-        __ctl_load(pgdir_k, 7, 7);
-        __ctl_load(pgdir_k, 13, 13);
-        __raw_local_irq_ssm(ssm_mask);
-
-        local_flush_tlb();
 }
-#endif /* CONFIG_64BIT */
 
 void __init mem_init(void)
 {
@@ -269,6 +186,8 @@ void __init mem_init(void)
         printk("Write protected kernel read-only data: %#lx - %#lx\n",
                (unsigned long)&__start_rodata,
                PFN_ALIGN((unsigned long)&__end_rodata) - 1);
+        printk("Virtual memmap size: %ldk\n",
+               (max_pfn * sizeof(struct page)) >> 10);
 }
 
 void free_initmem(void)