Re: mips64 vm problems?

[Ralf Baechle <ralf@xxxxxxxxxxx>]

On Fri, Jun 15, 2001 at 11:12:30AM -0700, John Hawkes wrote:

> Do you understand the nature of the mips64 vm problems?  Do you have any
> idea how long it will take to fix?

Exactly that long.  I found that vmalloc was already broken before the
recent changes which finally broke it in obvious ways.

Btw, I'm interested in the results of your research about the mips64 kernel,
that is where are problems with locking, how does it compare in performance
to Linux on other architectures etc.

  Ralf

Index: linux/arch/mips64/kernel/r4k_tlb.S
diff -u linux/arch/mips64/kernel/r4k_tlb.S:1.4 
linux/arch/mips64/kernel/r4k_tlb.S:1.5
--- linux/arch/mips64/kernel/r4k_tlb.S:1.4      Fri Feb 23 11:23:51 2001
+++ linux/arch/mips64/kernel/r4k_tlb.S  Sat Jun 16 02:43:08 2001
@@ -96,9 +96,6 @@
         */
        dmfc0   k0, CP0_BADVADDR
        dli     k1, VMALLOC_START
-       sltu    k1, k0, k1
-       bne     k1, zero, not_vmalloc
-        dli    k1, VMALLOC_START
 
        /*
         * Now find offset into kptbl.
@@ -114,20 +111,16 @@
         */
        dla     k0, ekptbl
        sltu    k0, k1, k0
-       beq     k0, zero, not_vmalloc
+       beqz    k0, not_vmalloc
 
        /*
         * Load cp0 registers.
         */
        ld      k0, 0(k1)                       # get even pte
        ld      k1, 8(k1)                       # get odd pte
-1:
+
+not_vmalloc:
        PTE_RELOAD k0 k1
        nop
        tlbwr
        eret
-not_vmalloc:
-       daddu   k0, zero, zero
-       daddu   k1, zero, zero
-       j       1b
-       nop
Index: linux/arch/mips64/mm/fault.c
diff -u linux/arch/mips64/mm/fault.c:1.17 linux/arch/mips64/mm/fault.c:1.18
--- linux/arch/mips64/mm/fault.c:1.17   Thu May 31 17:21:21 2001
+++ linux/arch/mips64/mm/fault.c        Sat Jun 16 02:44:40 2001
@@ -242,31 +242,5 @@
        return;
 
 vmalloc_fault:
-       {
-               /*
-                * Synchronize this task's top level page-table
-                * with the 'reference' page table.
-                */
-               int offset = pgd_index(address);
-               pgd_t *pgd, *pgd_k;
-               pmd_t *pmd, *pmd_k;
-
-               pgd = tsk->active_mm->pgd + offset;
-               pgd_k = init_mm.pgd + offset;
-
-               if (!pgd_present(*pgd)) {
-                       if (!pgd_present(*pgd_k))
-                               goto bad_area_nosemaphore;
-                       set_pgd(pgd, *pgd_k);
-                       return;
-               }
-
-               pmd = pmd_offset(pgd, address);
-               pmd_k = pmd_offset(pgd_k, address);
-
-               if (pmd_present(*pmd) || !pmd_present(*pmd_k))
-                       goto bad_area_nosemaphore;
-               set_pmd(pmd, *pmd_k);
-               return;
-       }
+       panic("Pagefault for kernel virtual memory");
 }
Index: linux/arch/mips64/sgi-ip27/ip27-memory.c
diff -u linux/arch/mips64/sgi-ip27/ip27-memory.c:1.14 
linux/arch/mips64/sgi-ip27/ip27-memory.c:1.15
--- linux/arch/mips64/sgi-ip27/ip27-memory.c:1.14       Thu Apr  5 05:35:18 2001
+++ linux/arch/mips64/sgi-ip27/ip27-memory.c    Sat Jun 16 02:45:44 2001
@@ -20,6 +20,7 @@
 #include <asm/bootinfo.h>
 #include <asm/addrspace.h>
 #include <asm/pgtable.h>
+#include <asm/pgalloc.h>
 #include <asm/sn/types.h>
 #include <asm/sn/addrs.h>
 #include <asm/sn/klconfig.h>
@@ -227,13 +228,24 @@
 
 void __init paging_init(void)
 {
+       pmd_t *pmd = kpmdtbl;
+       pte_t *pte = kptbl;
+
        cnodeid_t node;
        unsigned long zones_size[MAX_NR_ZONES] = {0, 0, 0};
+       int i;
 
        /* Initialize the entire pgd.  */
        pgd_init((unsigned long)swapper_pg_dir);
        pmd_init((unsigned long)invalid_pmd_table, (unsigned 
long)invalid_pte_table);
        memset((void *)invalid_pte_table, 0, sizeof(pte_t) * PTRS_PER_PTE);
+
+       /* This is for vmalloc  */
+       memset((void *)kptbl, 0, PAGE_SIZE << KPTBL_PAGE_ORDER);
+       memset((void *)kpmdtbl, 0, PAGE_SIZE);
+       pgd_set(swapper_pg_dir, kpmdtbl);
+       for (i = 0; i < (1 << KPTBL_PAGE_ORDER); pmd++,i++,pte+=PTRS_PER_PTE)
+               pmd_val(*pmd) = (unsigned long)pte;
 
        for (node = 0; node < numnodes; node++) {
                pfn_t start_pfn = slot_getbasepfn(node, 0);