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Several changes (sorry!): 

Refuse to clear the modified bit on a page if it has a writeable kernel
mapping.  I'm not sure this is the right thing to do, but since further
writes to the page won't set the bit again, it's safer than clearing it,
and makes NFS writes work properly.

Add debugging code for modified-bit emulation, which checksums
allegedly-unmodified pages to see if they're _really_ unmodified.
Disabled by default because it's slow.

In the process, fix a bug in pv_release whereby the modified bit for a
page got cleared when its last mapping was removed.  This seems to finish
the NFS write fixes started by the first change above.
This commit is contained in:
bjh21 2001-11-18 15:47:36 +00:00
parent 81611660e5
commit b5dff60f89
1 changed files with 68 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

75
sys/arch/arm26/arm26/pmap.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: pmap.c,v 1.34 2001/11/16 13:47:06 bjh21 Exp $ */
/* $NetBSD: pmap.c,v 1.35 2001/11/18 15:47:36 bjh21 Exp $ */
/*-
* Copyright (c) 1997, 1998, 2000 Ben Harris
* All rights reserved.
@ -105,7 +105,7 @@
#include <sys/param.h>
__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.34 2001/11/16 13:47:06 bjh21 Exp $");
__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.35 2001/11/18 15:47:36 bjh21 Exp $");
#include <sys/kernel.h> /* for cold */
#include <sys/malloc.h>
@ -121,6 +121,10 @@ __KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.34 2001/11/16 13:47:06 bjh21 Exp $");
#include <arch/arm26/arm26/cpuvar.h>
#ifdef PMAP_DEBUG_MODIFIED
#include <sys/md4.h>
#endif
/*
* We store all the mapping information in the pv_table, and the pmaps
* just contain references to it. This is suggested in the Daemon
@ -138,9 +142,13 @@ struct pv_entry {
u_int8_t pv_vflags; /* Per-mapping flags */
#define PV_WIRED 0x01 /* This is a wired mapping */
#define PV_UNMANAGED 0x02 /* Mapping was entered by pmap_kenter_*() */
/* From pv_pflags onwards is per-physical-page state. */
u_int8_t pv_pflags; /* Per-physical-page flags */
#define PV_REFERENCED 0x01
#define PV_MODIFIED 0x02
#ifdef PMAP_DEBUG_MODIFIED
unsigned char pv_md4sum[16];
#endif
};
#define PM_NENTRIES 1024
@ -200,6 +208,10 @@ static caddr_t pmap_find(paddr_t);
static void pmap_update_page(int);
#ifdef PMAP_DEBUG_MODIFIED
static void pmap_md4_page(unsigned char [16], paddr_t);
#endif
/*
* No-one else wanted to take responsibility for the MEMC control register,
* so it's ended up here.
@ -245,6 +257,10 @@ pmap_bootstrap(int npages, paddr_t zp_physaddr)
pv_table =
(struct pv_entry *)uvm_pageboot_alloc(pv_table_size);
bzero(pv_table, pv_table_size);
#ifdef PMAP_DEBUG_MODIFIED
for (i = 0; i < physmem; i++)
pv_table[i].pv_pflags |= PV_MODIFIED;
#endif
/* Set up the kernel's pmap */
pmap = pmap_kernel();
@ -598,13 +614,12 @@ pv_release(pmap_t pmap, int ppn, int lpn)
if (npv) {
UVMHIST_LOG(pmaphist, "pv=%p; pull-up", pv, 0, 0, 0);
/* Pull up first entry from chain. */
npv->pv_pflags = pv->pv_pflags;
*pv = *npv;
memcpy(pv, npv, offsetof(struct pv_entry, pv_pflags));
pv->pv_pmap->pm_entries[pv->pv_lpn] = pv;
pv_free(npv);
} else {
UVMHIST_LOG(pmaphist, "pv=%p; empty", pv, 0, 0, 0);
bzero(pv, sizeof(*pv));
memset(pv, 0, offsetof(struct pv_entry, pv_pflags));
}
} else {
for (npv = pv->pv_next; npv; npv = npv->pv_next) {
@ -764,11 +779,33 @@ pmap_is_modified(page)
struct vm_page *page;
{
int ppn;
boolean_t rv;
#ifdef PMAP_DEBUG_MODIFIED
unsigned char digest[16];
#endif
UVMHIST_FUNC("pmap_is_modified");
UVMHIST_CALLED(pmaphist);
ppn = atop(page->phys_addr);
return (pv_table[ppn].pv_pflags & PV_MODIFIED) != 0;
rv = (pv_table[ppn].pv_pflags & PV_MODIFIED) != 0;
#ifdef PMAP_DEBUG_MODIFIED
if (!rv) {
pmap_md4_page(digest, page->phys_addr);
if (memcmp(digest, pv_table[ppn].pv_md4sum, 16) != 0) {
int i;
printf("page %p modified bit wrong\n", page);
printf("then = ");
for (i = 0; i < 16; i++)
printf("%02x", pv_table[ppn].pv_md4sum[i]);
printf("\n now = ");
for (i = 0; i < 16; i++)
printf("%02x", digest[i]);
printf("\n");
}
}
#endif
return rv;
}
inline boolean_t
@ -807,12 +844,22 @@ pmap_clear_modify(struct vm_page *page)
{
int ppn;
boolean_t rv;
struct pv_entry *pv;
UVMHIST_FUNC("pmap_clear_modify");
UVMHIST_CALLED(pmaphist);
ppn = atop(page->phys_addr);
rv = pmap_is_modified(page);
#ifdef PMAP_DEBUG_MODIFIED
pmap_md4_page(pv_table[ppn].pv_md4sum, ptoa(ppn));
#endif
if (rv) {
for (pv = &pv_table[ppn]; pv != NULL; pv = pv->pv_next)
if (pv->pv_pmap == pmap_kernel() &&
(pv->pv_prot & VM_PROT_WRITE)) {
printf("clear_modify on k-writable page\n");
return rv;
}
pv_table[ppn].pv_pflags &= ~PV_MODIFIED;
pmap_update_page(ppn);
}
@ -855,7 +902,7 @@ pmap_fault(struct pmap *pmap, vaddr_t va, vm_prot_t atype)
return FALSE;
ppn = pv->pv_ppn;
ppv = &pv_table[ppn];
UVMHIST_LOG(pmaphist,
UVMHIST_LOG(pmaphist,
"pmap = %p, lpn = %d, ppn = %d, atype = 0x%x",
pmap, lpn, ppn, atype);
if (pmap != pmap_kernel()) {
@ -1052,6 +1099,20 @@ pmap_copy_page(paddr_t src, paddr_t dest)
pmap_update_page(dppn);
}
#ifdef PMAP_DEBUG_MODIFIED
static void
pmap_md4_page(unsigned char digest[16], paddr_t pa)
{
MD4_CTX context;
UVMHIST_FUNC("pmap_md4_page");
UVMHIST_CALLED(pmaphist);
MD4Init(&context);
MD4Update(&context, pmap_find(pa), PAGE_SIZE);
MD4Final(digest, &context);
}
#endif
/*
* This is meant to return the range of kernel vm that is available
* after loading the kernel. Since NetBSD/arm26 runs the kernel from