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xen: use spin_lock_nest_lock when pinning a pagetable 

When pinning/unpinning a pagetable with split pte locks, we can end up
holding multiple pte locks at once (we need to hold the locks while
there's a pending batched hypercall affecting the pte page).  Because
all the pte locks are in the same lock class, lockdep thinks that
we're potentially taking a lock recursively.

This warning is spurious because we always take the pte locks while
holding mm->page_table_lock.  lockdep now has spin_lock_nest_lock to
express this kind of dominant lock use, so use it here so that lockdep
knows what's going on.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Jeremy Fitzhardinge 2008-10-08 13:01:39 -07:00 committed by Ingo Molnar
parent d19c8e516e
commit eefb47f6a1
2 changed files with 48 additions and 29 deletions
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74
arch/x86/xen/mmu.c
View File

@ -651,9 +651,12 @@ void xen_set_pgd(pgd_t *ptr, pgd_t val)
* For 64-bit, we must skip the Xen hole in the middle of the address
* space, just after the big x86-64 virtual hole.
*/
static int xen_pgd_walk(pgd_t *pgd, int (*func)(struct page *, enum pt_level),
static int xen_pgd_walk(struct mm_struct *mm,
int (*func)(struct mm_struct *mm, struct page *,
enum pt_level),
unsigned long limit)
{
pgd_t *pgd = mm->pgd;
int flush = 0;
unsigned hole_low, hole_high;
unsigned pgdidx_limit, pudidx_limit, pmdidx_limit;
@ -698,7 +701,7 @@ static int xen_pgd_walk(pgd_t *pgd, int (*func)(struct page *, enum pt_level),
pud = pud_offset(&pgd[pgdidx], 0);
if (PTRS_PER_PUD > 1) /* not folded */
flush |= (*func)(virt_to_page(pud), PT_PUD);
flush |= (*func)(mm, virt_to_page(pud), PT_PUD);
for (pudidx = 0; pudidx < PTRS_PER_PUD; pudidx++) {
pmd_t *pmd;
@ -713,7 +716,7 @@ static int xen_pgd_walk(pgd_t *pgd, int (*func)(struct page *, enum pt_level),
pmd = pmd_offset(&pud[pudidx], 0);
if (PTRS_PER_PMD > 1) /* not folded */
flush |= (*func)(virt_to_page(pmd), PT_PMD);
flush |= (*func)(mm, virt_to_page(pmd), PT_PMD);
for (pmdidx = 0; pmdidx < PTRS_PER_PMD; pmdidx++) {
struct page *pte;
@ -727,7 +730,7 @@ static int xen_pgd_walk(pgd_t *pgd, int (*func)(struct page *, enum pt_level),
continue;
pte = pmd_page(pmd[pmdidx]);
flush |= (*func)(pte, PT_PTE);
flush |= (*func)(mm, pte, PT_PTE);
}
}
}
@ -735,20 +738,20 @@ static int xen_pgd_walk(pgd_t *pgd, int (*func)(struct page *, enum pt_level),
out:
/* Do the top level last, so that the callbacks can use it as
a cue to do final things like tlb flushes. */
flush |= (*func)(virt_to_page(pgd), PT_PGD);
flush |= (*func)(mm, virt_to_page(pgd), PT_PGD);
return flush;
}
/* If we're using split pte locks, then take the page's lock and
return a pointer to it. Otherwise return NULL. */
static spinlock_t *xen_pte_lock(struct page *page)
static spinlock_t *xen_pte_lock(struct page *page, struct mm_struct *mm)
{
spinlock_t *ptl = NULL;
#if USE_SPLIT_PTLOCKS
ptl = __pte_lockptr(page);
spin_lock(ptl);
spin_lock_nest_lock(ptl, &mm->page_table_lock);
#endif
return ptl;
@ -772,7 +775,8 @@ static void xen_do_pin(unsigned level, unsigned long pfn)
MULTI_mmuext_op(mcs.mc, op, 1, NULL, DOMID_SELF);
}
static int xen_pin_page(struct page *page, enum pt_level level)
static int xen_pin_page(struct mm_struct *mm, struct page *page,
enum pt_level level)
{
unsigned pgfl = TestSetPagePinned(page);
int flush;
@ -813,7 +817,7 @@ static int xen_pin_page(struct page *page, enum pt_level level)
*/
ptl = NULL;
if (level == PT_PTE)
ptl = xen_pte_lock(page);
ptl = xen_pte_lock(page, mm);
MULTI_update_va_mapping(mcs.mc, (unsigned long)pt,
pfn_pte(pfn, PAGE_KERNEL_RO),
@ -834,11 +838,11 @@ static int xen_pin_page(struct page *page, enum pt_level level)
/* This is called just after a mm has been created, but it has not
been used yet. We need to make sure that its pagetable is all
read-only, and can be pinned. */
void xen_pgd_pin(pgd_t *pgd)
static void __xen_pgd_pin(struct mm_struct *mm, pgd_t *pgd)
{
xen_mc_batch();
if (xen_pgd_walk(pgd, xen_pin_page, USER_LIMIT)) {
if (xen_pgd_walk(mm, xen_pin_page, USER_LIMIT)) {
/* re-enable interrupts for kmap_flush_unused */
xen_mc_issue(0);
kmap_flush_unused();
@ -852,25 +856,35 @@ void xen_pgd_pin(pgd_t *pgd)
xen_do_pin(MMUEXT_PIN_L4_TABLE, PFN_DOWN(__pa(pgd)));
if (user_pgd) {
xen_pin_page(virt_to_page(user_pgd), PT_PGD);
xen_pin_page(mm, virt_to_page(user_pgd), PT_PGD);
xen_do_pin(MMUEXT_PIN_L4_TABLE, PFN_DOWN(__pa(user_pgd)));
}
}
#else /* CONFIG_X86_32 */
#ifdef CONFIG_X86_PAE
/* Need to make sure unshared kernel PMD is pinnable */
xen_pin_page(virt_to_page(pgd_page(pgd[pgd_index(TASK_SIZE)])), PT_PMD);
xen_pin_page(mm, virt_to_page(pgd_page(pgd[pgd_index(TASK_SIZE)])),
PT_PMD);
#endif
xen_do_pin(MMUEXT_PIN_L3_TABLE, PFN_DOWN(__pa(pgd)));
#endif /* CONFIG_X86_64 */
xen_mc_issue(0);
}
static void xen_pgd_pin(struct mm_struct *mm)
{
__xen_pgd_pin(mm, mm->pgd);
}
/*
* On save, we need to pin all pagetables to make sure they get their
* mfns turned into pfns. Search the list for any unpinned pgds and pin
* them (unpinned pgds are not currently in use, probably because the
* process is under construction or destruction).
*
* Expected to be called in stop_machine() ("equivalent to taking
* every spinlock in the system"), so the locking doesn't really
* matter all that much.
*/
void xen_mm_pin_all(void)
{
@ -881,7 +895,7 @@ void xen_mm_pin_all(void)
list_for_each_entry(page, &pgd_list, lru) {
if (!PagePinned(page)) {
xen_pgd_pin((pgd_t *)page_address(page));
__xen_pgd_pin(&init_mm, (pgd_t *)page_address(page));
SetPageSavePinned(page);
}
}
@ -894,7 +908,8 @@ void xen_mm_pin_all(void)
* that's before we have page structures to store the bits. So do all
* the book-keeping now.
*/
static __init int xen_mark_pinned(struct page *page, enum pt_level level)
static __init int xen_mark_pinned(struct mm_struct *mm, struct page *page,
enum pt_level level)
{
SetPagePinned(page);
return 0;
@ -902,10 +917,11 @@ static __init int xen_mark_pinned(struct page *page, enum pt_level level)
void __init xen_mark_init_mm_pinned(void)
{
xen_pgd_walk(init_mm.pgd, xen_mark_pinned, FIXADDR_TOP);
xen_pgd_walk(&init_mm, xen_mark_pinned, FIXADDR_TOP);
}
static int xen_unpin_page(struct page *page, enum pt_level level)
static int xen_unpin_page(struct mm_struct *mm, struct page *page,
enum pt_level level)
{
unsigned pgfl = TestClearPagePinned(page);
@ -923,7 +939,7 @@ static int xen_unpin_page(struct page *page, enum pt_level level)
* partially-pinned state.
*/
if (level == PT_PTE) {
ptl = xen_pte_lock(page);
ptl = xen_pte_lock(page, mm);
if (ptl)
xen_do_pin(MMUEXT_UNPIN_TABLE, pfn);
@ -945,7 +961,7 @@ static int xen_unpin_page(struct page *page, enum pt_level level)
}
/* Release a pagetables pages back as normal RW */
static void xen_pgd_unpin(pgd_t *pgd)
static void __xen_pgd_unpin(struct mm_struct *mm, pgd_t *pgd)
{
xen_mc_batch();
@ -957,21 +973,27 @@ static void xen_pgd_unpin(pgd_t *pgd)
if (user_pgd) {
xen_do_pin(MMUEXT_UNPIN_TABLE, PFN_DOWN(__pa(user_pgd)));
xen_unpin_page(virt_to_page(user_pgd), PT_PGD);
xen_unpin_page(mm, virt_to_page(user_pgd), PT_PGD);
}
}
#endif
#ifdef CONFIG_X86_PAE
/* Need to make sure unshared kernel PMD is unpinned */
xen_unpin_page(virt_to_page(pgd_page(pgd[pgd_index(TASK_SIZE)])), PT_PMD);
xen_unpin_page(mm, virt_to_page(pgd_page(pgd[pgd_index(TASK_SIZE)])),
PT_PMD);
#endif
xen_pgd_walk(pgd, xen_unpin_page, USER_LIMIT);
xen_pgd_walk(mm, xen_unpin_page, USER_LIMIT);
xen_mc_issue(0);
}
static void xen_pgd_unpin(struct mm_struct *mm)
{
__xen_pgd_unpin(mm, mm->pgd);
}
/*
* On resume, undo any pinning done at save, so that the rest of the
* kernel doesn't see any unexpected pinned pagetables.
@ -986,7 +1008,7 @@ void xen_mm_unpin_all(void)
list_for_each_entry(page, &pgd_list, lru) {
if (PageSavePinned(page)) {
BUG_ON(!PagePinned(page));
xen_pgd_unpin((pgd_t *)page_address(page));
__xen_pgd_unpin(&init_mm, (pgd_t *)page_address(page));
ClearPageSavePinned(page);
}
}
@ -997,14 +1019,14 @@ void xen_mm_unpin_all(void)
void xen_activate_mm(struct mm_struct *prev, struct mm_struct *next)
{
spin_lock(&next->page_table_lock);
xen_pgd_pin(next->pgd);
xen_pgd_pin(next);
spin_unlock(&next->page_table_lock);
}
void xen_dup_mmap(struct mm_struct *oldmm, struct mm_struct *mm)
{
spin_lock(&mm->page_table_lock);
xen_pgd_pin(mm->pgd);
xen_pgd_pin(mm);
spin_unlock(&mm->page_table_lock);
}
@ -1095,7 +1117,7 @@ void xen_exit_mmap(struct mm_struct *mm)
/* pgd may not be pinned in the error exit path of execve */
if (xen_page_pinned(mm->pgd))
xen_pgd_unpin(mm->pgd);
xen_pgd_unpin(mm);
spin_unlock(&mm->page_table_lock);
}

3
arch/x86/xen/mmu.h
View File

@ -18,9 +18,6 @@ void xen_activate_mm(struct mm_struct *prev, struct mm_struct *next);
void xen_dup_mmap(struct mm_struct *oldmm, struct mm_struct *mm);
void xen_exit_mmap(struct mm_struct *mm);
void xen_pgd_pin(pgd_t *pgd);
//void xen_pgd_unpin(pgd_t *pgd);
pteval_t xen_pte_val(pte_t);
pmdval_t xen_pmd_val(pmd_t);
pgdval_t xen_pgd_val(pgd_t);