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The Xen pmap doesn't support superpages. So, there is no point in it

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initializing structures, like the pv table, that are only used to
implement superpages.  In fact, some of the unnecessary code in
pmap_init() was actually doing harm.  It was preventing the kernel from
booting on virtual machines with more than 768 MB of memory.

Tested by:	sbruno
This commit is contained in:
Alan Cox 2011-12-20 20:16:12 +00:00
parent f6ccfb42a2
commit 971238ae48
1 changed files with 2 additions and 51 deletions
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53
sys/i386/xen/pmap.c
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@ -184,9 +184,6 @@ __FBSDID("$FreeBSD$");
#define PV_STAT(x) do { } while (0)
#endif
#define pa_index(pa) ((pa) >> PDRSHIFT)
#define pa_to_pvh(pa) (&pv_table[pa_index(pa)])
/*
* Get PDEs and PTEs for user/kernel address space
*/
@ -230,7 +227,6 @@ static int pat_works; /* Is page attribute table sane? */
* Data for the pv entry allocation mechanism
*/
static int pv_entry_count = 0, pv_entry_max = 0, pv_entry_high_water = 0;
static struct md_page *pv_table;
static int shpgperproc = PMAP_SHPGPERPROC;
struct pv_chunk *pv_chunkbase; /* KVA block for pv_chunks */
@ -278,9 +274,6 @@ SYSCTL_INT(_debug, OID_AUTO, PMAP1unchanged, CTLFLAG_RD,
static struct mtx PMAP2mutex;
static SYSCTL_NODE(_vm, OID_AUTO, pmap, CTLFLAG_RD, 0, "VM/pmap parameters");
static int pg_ps_enabled;
SYSCTL_INT(_vm_pmap, OID_AUTO, pg_ps_enabled, CTLFLAG_RDTUN, &pg_ps_enabled, 0,
"Are large page mappings enabled?");
SYSCTL_INT(_vm_pmap, OID_AUTO, pv_entry_max, CTLFLAG_RD, &pv_entry_max, 0,
"Max number of PV entries");
@ -636,24 +629,8 @@ pmap_ptelist_init(vm_offset_t *head, void *base, int npages)
void
pmap_init(void)
{
vm_page_t mpte;
vm_size_t s;
int i, pv_npg;
/*
* Initialize the vm page array entries for the kernel pmap's
* page table pages.
*/
for (i = 0; i < nkpt; i++) {
mpte = PHYS_TO_VM_PAGE(xpmap_mtop(PTD[i + KPTDI] & PG_FRAME));
KASSERT(mpte >= vm_page_array &&
mpte < &vm_page_array[vm_page_array_size],
("pmap_init: page table page is out of range"));
mpte->pindex = i + KPTDI;
mpte->phys_addr = xpmap_mtop(PTD[i + KPTDI] & PG_FRAME);
}
/*
* Initialize the address space (zone) for the pv entries. Set a
* high water mark so that the system can recover from excessive
* numbers of pv entries.
@ -664,26 +641,6 @@ pmap_init(void)
pv_entry_max = roundup(pv_entry_max, _NPCPV);
pv_entry_high_water = 9 * (pv_entry_max / 10);
/*
* Are large page mappings enabled?
*/
TUNABLE_INT_FETCH("vm.pmap.pg_ps_enabled", &pg_ps_enabled);
/*
* Calculate the size of the pv head table for superpages.
*/
for (i = 0; phys_avail[i + 1]; i += 2);
pv_npg = round_4mpage(phys_avail[(i - 2) + 1]) / NBPDR;
/*
* Allocate memory for the pv head table for superpages.
*/
s = (vm_size_t)(pv_npg * sizeof(struct md_page));
s = round_page(s);
pv_table = (struct md_page *)kmem_alloc(kernel_map, s);
for (i = 0; i < pv_npg; i++)
TAILQ_INIT(&pv_table[i].pv_list);
pv_maxchunks = MAX(pv_entry_max / _NPCPV, maxproc);
pv_chunkbase = (struct pv_chunk *)kmem_alloc_nofault(kernel_map,
PAGE_SIZE * pv_maxchunks);
@ -3448,21 +3405,15 @@ pmap_page_wired_mappings(vm_page_t m)
}
/*
* Returns TRUE if the given page is mapped individually or as part of
* a 4mpage. Otherwise, returns FALSE.
* Returns TRUE if the given page is mapped. Otherwise, returns FALSE.
*/
boolean_t
pmap_page_is_mapped(vm_page_t m)
{
boolean_t rv;
if ((m->oflags & VPO_UNMANAGED) != 0)
return (FALSE);
vm_page_lock_queues();
rv = !TAILQ_EMPTY(&m->md.pv_list) ||
!TAILQ_EMPTY(&pa_to_pvh(VM_PAGE_TO_PHYS(m))->pv_list);
vm_page_unlock_queues();
return (rv);
return (!TAILQ_EMPTY(&m->md.pv_list));
}
/*