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[src/trunk]: src/sys/arch/x86 PR kern/55071 (Panic shortly after running X11 ...
details: https://anonhg.NetBSD.org/src/rev/0073b25fe5b6
branches: trunk
changeset: 1008200:0073b25fe5b6
user: ad <ad%NetBSD.org@localhost>
date: Sat Mar 14 18:24:10 2020 +0000
description:
PR kern/55071 (Panic shortly after running X11 due to kernel diagnostic assertion "mutex_owned(&pp->pp_lock)")
- Fix a locking bug in pmap_pp_clear_attrs() and in pmap_pp_remove() do the
TLB shootdown while still holding the target pmap's lock.
Also:
- Finish PV list locking for x86 & update comments around same.
- Keep track of the min/max index of PTEs inserted into each PTP, and use
that to clip ranges of VAs passed to pmap_remove_ptes().
- Based on the above, implement a pmap_remove_all() for x86 that clears out
the pmap in a single pass. Makes exit() / fork() much cheaper.
diffstat:
sys/arch/x86/include/pmap.h | 6 +-
sys/arch/x86/include/pmap_pv.h | 21 +-
sys/arch/x86/x86/pmap.c | 680 ++++++++++++++++++++++++++++------------
3 files changed, 489 insertions(+), 218 deletions(-)
diffs (truncated from 1217 to 300 lines):
diff -r ec42ae4d8511 -r 0073b25fe5b6 sys/arch/x86/include/pmap.h
--- a/sys/arch/x86/include/pmap.h Sat Mar 14 18:08:38 2020 +0000
+++ b/sys/arch/x86/include/pmap.h Sat Mar 14 18:24:10 2020 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: pmap.h,v 1.112 2020/03/14 14:05:44 ad Exp $ */
+/* $NetBSD: pmap.h,v 1.113 2020/03/14 18:24:10 ad Exp $ */
/*
* Copyright (c) 1997 Charles D. Cranor and Washington University.
@@ -248,6 +248,8 @@
* (the other object locks are only used when uvm_pagealloc is called)
*/
+struct pv_page;
+
struct pmap {
struct uvm_object pm_obj[PTP_LEVELS-1];/* objects for lvl >= 1) */
LIST_ENTRY(pmap) pm_list; /* list of all pmaps */
@@ -256,11 +258,11 @@
struct vm_page *pm_ptphint[PTP_LEVELS-1];
/* pointer to a PTP in our pmap */
struct pmap_statistics pm_stats; /* pmap stats */
+ struct pv_entry *pm_pve; /* spare pv_entry */
#if !defined(__x86_64__)
vaddr_t pm_hiexec; /* highest executable mapping */
#endif /* !defined(__x86_64__) */
- struct lwp *pm_remove_all; /* who's emptying the pmap */
union descriptor *pm_ldt; /* user-set LDT */
size_t pm_ldt_len; /* size of LDT in bytes */
diff -r ec42ae4d8511 -r 0073b25fe5b6 sys/arch/x86/include/pmap_pv.h
--- a/sys/arch/x86/include/pmap_pv.h Sat Mar 14 18:08:38 2020 +0000
+++ b/sys/arch/x86/include/pmap_pv.h Sat Mar 14 18:24:10 2020 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: pmap_pv.h,v 1.13 2020/03/10 22:38:41 ad Exp $ */
+/* $NetBSD: pmap_pv.h,v 1.14 2020/03/14 18:24:10 ad Exp $ */
/*-
* Copyright (c)2008 YAMAMOTO Takashi,
@@ -34,6 +34,7 @@
#include <sys/rbtree.h>
struct vm_page;
+struct pmap_page;
/*
* structures to track P->V mapping
@@ -51,14 +52,14 @@
};
/*
- * pv_entry: plug pv_pte into lists.
+ * pv_entry: plug pv_pte into lists. 32 bytes on i386, 64 on amd64.
*/
struct pv_entry {
struct pv_pte pve_pte; /* should be the first member */
LIST_ENTRY(pv_entry) pve_list; /* on pmap_page::pp_pvlist */
rb_node_t pve_rb; /* red-black tree node */
- uintptr_t pve_padding; /* unused */
+ struct pmap_page *pve_pp; /* backpointer to mapped page */
};
#define pve_next pve_list.le_next
@@ -71,16 +72,14 @@
/* PTPs */
rb_tree_t rb;
- /* PTPs */
+ /* PTPs, when being freed */
LIST_ENTRY(vm_page) link;
- /* Non-PTPs */
+ /* Non-PTPs (i.e. normal pages) */
struct {
- /* PP_EMBEDDED */
struct pv_pte pte;
-
LIST_HEAD(, pv_entry) pvlist;
- uint8_t flags;
+ uint8_t embedded;
uint8_t attrs;
} s;
} pp_u;
@@ -89,7 +88,7 @@
#define pp_link pp_u.link
#define pp_pte pp_u.s.pte
#define pp_pvlist pp_u.s.pvlist
-#define pp_pflags pp_u.s.flags
+#define pp_embedded pp_u.s.embedded
#define pp_attrs pp_u.s.attrs
};
@@ -97,10 +96,6 @@
#define PP_ATTRS_A 0x02 /* Accessed */
#define PP_ATTRS_W 0x04 /* Writable */
-/* pp_flags */
-#define PP_EMBEDDED 1
-#define PP_FREEING 2
-
#define PMAP_PAGE_INIT(pp) \
do { \
LIST_INIT(&(pp)->pp_pvlist); \
diff -r ec42ae4d8511 -r 0073b25fe5b6 sys/arch/x86/x86/pmap.c
--- a/sys/arch/x86/x86/pmap.c Sat Mar 14 18:08:38 2020 +0000
+++ b/sys/arch/x86/x86/pmap.c Sat Mar 14 18:24:10 2020 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: pmap.c,v 1.365 2020/03/14 14:05:44 ad Exp $ */
+/* $NetBSD: pmap.c,v 1.366 2020/03/14 18:24:10 ad Exp $ */
/*
* Copyright (c) 2008, 2010, 2016, 2017, 2019, 2020 The NetBSD Foundation, Inc.
@@ -130,7 +130,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.365 2020/03/14 14:05:44 ad Exp $");
+__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.366 2020/03/14 18:24:10 ad Exp $");
#include "opt_user_ldt.h"
#include "opt_lockdebug.h"
@@ -224,23 +224,39 @@
/*
* Locking
*
- * We have the following locks that we must contend with, listed in the
- * order that they must be acquired:
+ * We have the following locks that we must deal with, listed in the order
+ * that they are acquired:
+ *
+ * pg->uobject->vmobjlock, pg->uanon->an_lock
*
- * - pg->uobject->vmobjlock, pg->uanon->an_lock
- * These per-object locks are taken by the VM system before calling into
- * the pmap module. Holding them prevents concurrent operations on the
- * given page or set of pages.
+ * For managed pages, these per-object locks are taken by the VM system
+ * before calling into the pmap module - either a read or write hold.
+ * The lock hold prevent pages from changing identity while the pmap is
+ * operating on them. For example, the same lock is held across a call
+ * to pmap_remove() and the following call to pmap_update(), so that a
+ * page does not gain a new identity while its TLB visibility is stale.
+ *
+ * pmap->pm_lock
*
- * - pmap->pm_lock (per pmap)
- * This lock protects the fields in the pmap structure including the
- * non-kernel PDEs in the PDP, the PTEs, and the PVE radix tree. For
- * modifying kernel PTEs it is not required as kernel PDEs are never
- * freed, and the kernel is expected to be self consistent.
+ * This lock protects the fields in the pmap structure including the
+ * non-kernel PDEs in the PDP, the PTEs, and PTPs and connected data
+ * structures. For modifying unmanaged kernel PTEs it is not needed as
+ * kernel PDEs are never freed, and the kernel is expected to be self
+ * consistent (and the lock can't be taken for unmanaged kernel PTEs,
+ * because they can be modified from interrupt context).
+ *
+ * pmaps_lock
*
- * - pmaps_lock
- * This lock protects the list of active pmaps (headed by "pmaps"). We
- * lock it when adding or removing pmaps from this list.
+ * This lock protects the list of active pmaps (headed by "pmaps").
+ * It's acqired when adding or removing pmaps or adjusting kernel PDEs.
+ *
+ * pp_lock
+ *
+ * This per-page lock protects PV entry lists and the embedded PV entry
+ * in each vm_page, allowing for concurrent operation on pages by
+ * different pmaps. This is a spin mutex at IPL_VM, because at the
+ * points it is taken context switching is usually not tolerable, and
+ * spin mutexes must block out interrupts that could take kernel_lock.
*/
/* uvm_object is abused here to index pmap_pages; make assertions happy. */
@@ -530,7 +546,7 @@
{
KASSERT(mutex_owned(&pp->pp_lock));
- if ((pp->pp_pflags & PP_EMBEDDED) != 0) {
+ if (pp->pp_embedded) {
return &pp->pp_pte;
}
return pve_to_pvpte(LIST_FIRST(&pp->pp_pvlist));
@@ -543,7 +559,7 @@
KASSERT(mutex_owned(&pp->pp_lock));
KASSERT(pvpte != NULL);
if (pvpte == &pp->pp_pte) {
- KASSERT((pp->pp_pflags & PP_EMBEDDED) != 0);
+ KASSERT(pp->pp_embedded);
return pve_to_pvpte(LIST_FIRST(&pp->pp_pvlist));
}
return pve_to_pvpte(LIST_NEXT(pvpte_to_pve(pvpte), pve_list));
@@ -605,6 +621,82 @@
}
/*
+ * pmap_ptp_init: initialize new page table page
+ */
+static inline void
+pmap_ptp_init(struct vm_page *ptp)
+{
+ uint16_t *minidx, *maxidx;
+
+ minidx = (uint16_t *)&ptp->uanon;
+ maxidx = (uint16_t *)&ptp->uanon + 1;
+
+ *minidx = UINT16_MAX;
+ *maxidx = 0;
+ rb_tree_init(&VM_PAGE_TO_PP(ptp)->pp_rb, &pmap_rbtree_ops);
+}
+
+/*
+ * pmap_ptp_fini: finalize a page table page
+ */
+static inline void
+pmap_ptp_fini(struct vm_page *ptp)
+{
+
+ KASSERT(RB_TREE_MIN(&VM_PAGE_TO_PP(ptp)->pp_rb) == NULL);
+ ptp->uanon = NULL;
+}
+
+/*
+ * pmap_ptp_range_set: abuse ptp->uanon to record min/max idx of PTE
+ */
+static inline void
+pmap_ptp_range_set(struct vm_page *ptp, vaddr_t va)
+{
+ uint16_t *minidx, *maxidx;
+ u_int idx;
+
+ idx = pl1_pi(va);
+ KASSERT(idx < UINT16_MAX);
+ minidx = (uint16_t *)&ptp->uanon;
+ maxidx = (uint16_t *)&ptp->uanon + 1;
+
+ if (idx < *minidx) {
+ *minidx = idx;
+ }
+ if (idx > *maxidx) {
+ *maxidx = idx;
+ }
+}
+
+/*
+ * pmap_ptp_range_clip: abuse ptp->uanon to clip range of PTEs to remove
+ */
+static inline void
+pmap_ptp_range_clip(struct vm_page *ptp, vaddr_t *startva, vaddr_t *endva,
+ pt_entry_t **pte)
+{
+ vaddr_t sclip, eclip;
+
+ if (ptp == NULL) {
+ return;
+ }
+
+ sclip = (*startva & L2_FRAME) +
+ x86_ptob(*(uint16_t *)&ptp->uanon);
+ eclip = (*startva & L2_FRAME) +
+ x86_ptob(*((uint16_t *)&ptp->uanon + 1) + 1);
+
+ KASSERT(sclip < eclip);
+
+ sclip = (*startva < sclip ? sclip : *startva);
+ eclip = (*endva > eclip ? eclip : *endva);
+ *pte += (sclip - *startva) / PAGE_SIZE;
+ *startva = sclip;
+ *endva = eclip;
+}
+
+/*
* pmap_map_ptes: map a pmap's PTEs into KVM and lock them in
*
* there are several pmaps involved. some or all of them might be same.
@@ -656,7 +748,9 @@
* often the case during exit(), when we have switched
* to the kernel pmap in order to destroy a user pmap.
*/
- pmap_reactivate(pmap);
+ if (__predict_false(ci->ci_tlbstate != TLBSTATE_VALID)) {
+ pmap_reactivate(pmap);
+ }
*pmap2 = NULL;
} else {
/*
@@ -1771,7 +1865,7 @@
* The kernel doesn't keep track of PTPs, so there's nowhere handy
* to hang a tree of pv_entry records. Dynamically allocated
* pv_entry lists are not heavily used in the kernel's pmap (the
- * usual case is PP_EMBEDDED), so cop out and use a single RB tree
+ * usual case is embedded), so cop out and use a single RB tree
* to cover them.
*/
rb_tree_init(&pmap_kernel_rb, &pmap_rbtree_ops);
@@ -1857,28 +1951,6 @@
* p v _ e n t r y f u n c t i o n s
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