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Message-ID: <48ED11A3.3090605@goop.org>
Date: Wed, 08 Oct 2008 13:01:39 -0700
From: Jeremy Fitzhardinge <jeremy@...p.org>
To: Ingo Molnar <mingo@...e.hu>
CC: Peter Zijlstra <peterz@...radead.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH] 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@...rix.com>
---
arch/x86/xen/mmu.c | 74 +++++++++++++++++++++++++++++++++-------------------
arch/x86/xen/mmu.h | 3 --
2 files changed, 48 insertions(+), 29 deletions(-)
===================================================================
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -651,9 +651,12 @@
* 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 @@
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 @@
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 @@
continue;
pte = pmd_page(pmd[pmdidx]);
- flush |= (*func)(pte, PT_PTE);
+ flush |= (*func)(mm, pte, PT_PTE);
}
}
}
@@ -735,20 +738,20 @@
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 @@
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 @@
*/
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 @@
/* 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();
@@ -852,18 +856,24 @@
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);
}
/*
@@ -871,6 +881,10 @@
* 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 @@
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 @@
* 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 @@
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 @@
* 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 @@
}
/* 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();
@@ -957,19 +973,25 @@
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);
}
/*
@@ -986,7 +1008,7 @@
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_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 @@
/* 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);
}
===================================================================
--- a/arch/x86/xen/mmu.h
+++ b/arch/x86/xen/mmu.h
@@ -17,9 +17,6 @@
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);
--
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