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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] open-coded page list manipulation in shadow code
Hi,
At 11:50 +0100 on 27 Jan (1422355826), Tim Deegan wrote:
> Let me have a think about it on Thursday (assuming I don't have too
> many patch series to review by then!)
OK, here's what I have. It keeps the mechanism the same, threading on
the main page list entry, but tidies it up to use the page_list operations
rather than open-coding. I've tested it (lightly - basically jsut
boot testing) with 32bit, 32pae and 64bit Windows VMs (all SMP), with
bigmem=y and bigmem=n.
It was developed on top of your bigmem series, but it should apply OK
before patch 3/4, removing the need to nobble shadow-paging in that
patch.
Cheers,
Tim.
From 57d211e47ef42012791252b4897231b392b7aff7 Mon Sep 17 00:00:00 2001
From: Tim Deegan <tim@xxxxxxx>
Date: Thu, 29 Jan 2015 17:09:58 +0000
Subject: [PATCH] x86/shadow: Tidy up fragmentary page lists in multi-page
shadows.
Multi-page shadows are linked together using the 'list' field. When
those shadows are in the pinned list, the list fragments are spliced
into the pinned list; otherwise they have no associated list head.
Rework the code that handles these fragments to use the page_list
interface rather than manipulating the fields directly. This makes
the code cleaner, and allows the 'list' field to be either the
compact pdx form or a normal list_entry.
Signed-off-by: Tim Deegan <tim@xxxxxxx>
---
xen/arch/x86/mm/shadow/common.c | 42 +++--------
xen/arch/x86/mm/shadow/multi.c | 14 ++--
xen/arch/x86/mm/shadow/private.h | 151 ++++++++++++++++++++++-----------------
xen/include/xen/mm.h | 9 +++
4 files changed, 114 insertions(+), 102 deletions(-)
diff --git a/xen/arch/x86/mm/shadow/common.c b/xen/arch/x86/mm/shadow/common.c
index 61110bb..12a86c2 100644
--- a/xen/arch/x86/mm/shadow/common.c
+++ b/xen/arch/x86/mm/shadow/common.c
@@ -1220,33 +1220,6 @@ static unsigned int shadow_min_acceptable_pages(struct
domain *d)
return (vcpu_count * 128);
}
-/* Figure out the size (in pages) of a given shadow type */
-static inline u32
-shadow_size(unsigned int shadow_type)
-{
- static const u32 type_to_size[SH_type_unused] = {
- 1, /* SH_type_none */
- 2, /* SH_type_l1_32_shadow */
- 2, /* SH_type_fl1_32_shadow */
- 4, /* SH_type_l2_32_shadow */
- 1, /* SH_type_l1_pae_shadow */
- 1, /* SH_type_fl1_pae_shadow */
- 1, /* SH_type_l2_pae_shadow */
- 1, /* SH_type_l2h_pae_shadow */
- 1, /* SH_type_l1_64_shadow */
- 1, /* SH_type_fl1_64_shadow */
- 1, /* SH_type_l2_64_shadow */
- 1, /* SH_type_l2h_64_shadow */
- 1, /* SH_type_l3_64_shadow */
- 1, /* SH_type_l4_64_shadow */
- 1, /* SH_type_p2m_table */
- 1, /* SH_type_monitor_table */
- 1 /* SH_type_oos_snapshot */
- };
- ASSERT(shadow_type < SH_type_unused);
- return type_to_size[shadow_type];
-}
-
/* Dispatcher function: call the per-mode function that will unhook the
* non-Xen mappings in this top-level shadow mfn. With user_only == 1,
* unhooks only the user-mode mappings. */
@@ -1489,9 +1462,6 @@ mfn_t shadow_alloc(struct domain *d,
break;
}
- /* Page lists don't have pointers back to the head structure, so
- * it's safe to use a head structure on the stack to link the pages
- * together. */
INIT_PAGE_LIST_HEAD(&tmp_list);
/* Init page info fields and clear the pages */
@@ -1525,6 +1495,14 @@ mfn_t shadow_alloc(struct domain *d,
if ( shadow_type >= SH_type_min_shadow
&& shadow_type <= SH_type_max_shadow )
sp->u.sh.head = 1;
+
+#ifndef PAGE_LIST_NULL
+ /* The temporary list-head is on our stack. Blank out the
+ * pointers to it in the shadows, just to get a clean failure if
+ * we accidentally follow them. */
+ tmp_list.next->prev = tmp_list.prev->next = NULL;
+#endif
+
return page_to_mfn(sp);
}
@@ -1533,6 +1511,7 @@ mfn_t shadow_alloc(struct domain *d,
void shadow_free(struct domain *d, mfn_t smfn)
{
struct page_info *next = NULL, *sp = mfn_to_page(smfn);
+ struct page_list_head *pin_list;
unsigned int pages;
u32 shadow_type;
int i;
@@ -1544,6 +1523,7 @@ void shadow_free(struct domain *d, mfn_t smfn)
ASSERT(shadow_type != SH_type_none);
ASSERT(sp->u.sh.head || (shadow_type > SH_type_max_shadow));
pages = shadow_size(shadow_type);
+ pin_list = &d->arch.paging.shadow.pinned_shadows;
for ( i = 0; i < pages; i++ )
{
@@ -1564,7 +1544,7 @@ void shadow_free(struct domain *d, mfn_t smfn)
#endif
/* Get the next page before we overwrite the list header */
if ( i < pages - 1 )
- next = pdx_to_page(sp->list.next);
+ next = page_list_next(sp, pin_list);
/* Strip out the type: this is now a free shadow page */
sp->u.sh.type = sp->u.sh.head = 0;
/* Remember the TLB timestamp so we will know whether to flush
diff --git a/xen/arch/x86/mm/shadow/multi.c b/xen/arch/x86/mm/shadow/multi.c
index 65815bb..5fc10c9 100644
--- a/xen/arch/x86/mm/shadow/multi.c
+++ b/xen/arch/x86/mm/shadow/multi.c
@@ -428,20 +428,20 @@ sh_guest_get_eff_l1e(struct vcpu *v, unsigned long addr,
void *eff_l1e)
/* From one page of a multi-page shadow, find the next one */
static inline mfn_t sh_next_page(mfn_t smfn)
{
- mfn_t next;
- struct page_info *pg = mfn_to_page(smfn);
+ struct page_info *pg = mfn_to_page(smfn), *next;
+ struct page_list_head h = PAGE_LIST_HEAD_INIT(h);
ASSERT(pg->u.sh.type == SH_type_l1_32_shadow
|| pg->u.sh.type == SH_type_fl1_32_shadow
|| pg->u.sh.type == SH_type_l2_32_shadow);
ASSERT(pg->u.sh.type == SH_type_l2_32_shadow || pg->u.sh.head);
- ASSERT(pg->list.next != PAGE_LIST_NULL);
- next = _mfn(pdx_to_pfn(pg->list.next));
+ next = page_list_next(pg, &h);
- ASSERT(mfn_to_page(next)->u.sh.type == pg->u.sh.type);
- ASSERT(!mfn_to_page(next)->u.sh.head);
- return next;
+ ASSERT(next);
+ ASSERT(next->u.sh.type == pg->u.sh.type);
+ ASSERT(!next->u.sh.head);
+ return page_to_mfn(next);
}
static inline u32
diff --git a/xen/arch/x86/mm/shadow/private.h b/xen/arch/x86/mm/shadow/private.h
index b778fcf..b145cee 100644
--- a/xen/arch/x86/mm/shadow/private.h
+++ b/xen/arch/x86/mm/shadow/private.h
@@ -318,6 +318,33 @@ static inline int mfn_oos_may_write(mfn_t gmfn)
}
#endif /* (SHADOW_OPTIMIZATIONS & SHOPT_OUT_OF_SYNC) */
+/* Figure out the size (in pages) of a given shadow type */
+static inline u32
+shadow_size(unsigned int shadow_type)
+{
+ static const u32 type_to_size[SH_type_unused] = {
+ 1, /* SH_type_none */
+ 2, /* SH_type_l1_32_shadow */
+ 2, /* SH_type_fl1_32_shadow */
+ 4, /* SH_type_l2_32_shadow */
+ 1, /* SH_type_l1_pae_shadow */
+ 1, /* SH_type_fl1_pae_shadow */
+ 1, /* SH_type_l2_pae_shadow */
+ 1, /* SH_type_l2h_pae_shadow */
+ 1, /* SH_type_l1_64_shadow */
+ 1, /* SH_type_fl1_64_shadow */
+ 1, /* SH_type_l2_64_shadow */
+ 1, /* SH_type_l2h_64_shadow */
+ 1, /* SH_type_l3_64_shadow */
+ 1, /* SH_type_l4_64_shadow */
+ 1, /* SH_type_p2m_table */
+ 1, /* SH_type_monitor_table */
+ 1 /* SH_type_oos_snapshot */
+ };
+ ASSERT(shadow_type < SH_type_unused);
+ return type_to_size[shadow_type];
+}
+
/******************************************************************************
* Various function declarations
*/
@@ -586,22 +613,25 @@ prev_pinned_shadow(const struct page_info *page,
const struct domain *d)
{
struct page_info *p;
+ const struct page_list_head *pin_list;
+
+ pin_list = &d->arch.paging.shadow.pinned_shadows;
- if ( page == d->arch.paging.shadow.pinned_shadows.next )
+ if ( page_list_empty(pin_list) || page == page_list_first(pin_list) )
return NULL;
-
+
if ( page == NULL ) /* If no current place, start at the tail */
- p = d->arch.paging.shadow.pinned_shadows.tail;
+ p = page_list_last(pin_list);
else
- p = pdx_to_page(page->list.prev);
+ p = page_list_prev(page, pin_list);
/* Skip over the non-tail parts of multi-page shadows */
if ( p && p->u.sh.type == SH_type_l2_32_shadow )
{
- p = pdx_to_page(p->list.prev);
+ p = page_list_prev(p, pin_list);
ASSERT(p && p->u.sh.type == SH_type_l2_32_shadow);
- p = pdx_to_page(p->list.prev);
+ p = page_list_prev(p, pin_list);
ASSERT(p && p->u.sh.type == SH_type_l2_32_shadow);
- p = pdx_to_page(p->list.prev);
+ p = page_list_prev(p, pin_list);
ASSERT(p && p->u.sh.type == SH_type_l2_32_shadow);
}
ASSERT(!p || p->u.sh.head);
@@ -618,49 +648,48 @@ prev_pinned_shadow(const struct page_info *page,
* Returns 0 for failure, 1 for success. */
static inline int sh_pin(struct vcpu *v, mfn_t smfn)
{
- struct page_info *sp;
- struct page_list_head h, *pin_list;
-
+ struct page_info *sp[4];
+ struct page_list_head *pin_list;
+ unsigned int i, pages;
+ bool_t already_pinned;
+
ASSERT(mfn_valid(smfn));
- sp = mfn_to_page(smfn);
- ASSERT(sh_type_is_pinnable(v, sp->u.sh.type));
- ASSERT(sp->u.sh.head);
+ sp[0] = mfn_to_page(smfn);
+ pages = shadow_size(sp[0]->u.sh.type);
+ already_pinned = sp[0]->u.sh.pinned;
+ ASSERT(sh_type_is_pinnable(v, sp[0]->u.sh.type));
+ ASSERT(sp[0]->u.sh.head);
+
+ pin_list = &v->domain->arch.paging.shadow.pinned_shadows;
+ if ( already_pinned && sp[0] == page_list_first(pin_list) )
+ return 1;
/* Treat the up-to-four pages of the shadow as a unit in the list ops */
- h.next = h.tail = sp;
- if ( sp->u.sh.type == SH_type_l2_32_shadow )
+ for ( i = 1; i < pages; i++ )
{
- h.tail = pdx_to_page(h.tail->list.next);
- h.tail = pdx_to_page(h.tail->list.next);
- h.tail = pdx_to_page(h.tail->list.next);
- ASSERT(h.tail->u.sh.type == SH_type_l2_32_shadow);
+ sp[i] = page_list_next(sp[i - 1], pin_list);
+ ASSERT(sp[i]->u.sh.type == sp[0]->u.sh.type);
+ ASSERT(!sp[i]->u.sh.head);
}
- pin_list = &v->domain->arch.paging.shadow.pinned_shadows;
- if ( sp->u.sh.pinned )
+ if ( already_pinned )
{
- /* Already pinned: take it out of the pinned-list so it can go
- * at the front */
- if ( pin_list->next == h.next )
- return 1;
- page_list_prev(h.next, pin_list)->list.next = h.tail->list.next;
- if ( pin_list->tail == h.tail )
- pin_list->tail = page_list_prev(h.next, pin_list);
- else
- page_list_next(h.tail, pin_list)->list.prev = h.next->list.prev;
- h.tail->list.next = h.next->list.prev = PAGE_LIST_NULL;
+ /* Take it out of the pinned-list so it can go at the front */
+ for ( i = 0; i < pages; i++ )
+ page_list_del(sp[i], pin_list);
}
else
{
/* Not pinned: pin it! */
if ( !sh_get_ref(v, smfn, 0) )
return 0;
- sp->u.sh.pinned = 1;
- ASSERT(h.next->list.prev == PAGE_LIST_NULL);
- ASSERT(h.tail->list.next == PAGE_LIST_NULL);
+ sp[0]->u.sh.pinned = 1;
}
+
/* Put it at the head of the list of pinned shadows */
- page_list_splice(&h, pin_list);
+ for ( i = pages; i > 0; i-- )
+ page_list_add(sp[i - 1], pin_list);
+
return 1;
}
@@ -668,46 +697,40 @@ static inline int sh_pin(struct vcpu *v, mfn_t smfn)
* of pinned shadows, and release the extra ref. */
static inline void sh_unpin(struct vcpu *v, mfn_t smfn)
{
- struct page_list_head h, *pin_list;
- struct page_info *sp;
-
+ struct page_list_head tmp_list, *pin_list;
+ struct page_info *sp, *next;
+ unsigned int i, head_type;
+
ASSERT(mfn_valid(smfn));
sp = mfn_to_page(smfn);
+ head_type = sp->u.sh.type;
ASSERT(sh_type_is_pinnable(v, sp->u.sh.type));
ASSERT(sp->u.sh.head);
- /* Treat the up-to-four pages of the shadow as a unit in the list ops */
- h.next = h.tail = sp;
- if ( sp->u.sh.type == SH_type_l2_32_shadow )
- {
- h.tail = pdx_to_page(h.tail->list.next);
- h.tail = pdx_to_page(h.tail->list.next);
- h.tail = pdx_to_page(h.tail->list.next);
- ASSERT(h.tail->u.sh.type == SH_type_l2_32_shadow);
- }
- pin_list = &v->domain->arch.paging.shadow.pinned_shadows;
-
if ( !sp->u.sh.pinned )
return;
-
sp->u.sh.pinned = 0;
- /* Cut the sub-list out of the list of pinned shadows */
- if ( pin_list->next == h.next && pin_list->tail == h.tail )
- pin_list->next = pin_list->tail = NULL;
- else
+ /* Cut the sub-list out of the list of pinned shadows,
+ * stitching it back into a list fragment of its own. */
+ pin_list = &v->domain->arch.paging.shadow.pinned_shadows;
+ INIT_PAGE_LIST_HEAD(&tmp_list);
+ for ( i = 0; i < shadow_size(head_type); i++ )
{
- if ( pin_list->next == h.next )
- pin_list->next = page_list_next(h.tail, pin_list);
- else
- page_list_prev(h.next, pin_list)->list.next = h.tail->list.next;
- if ( pin_list->tail == h.tail )
- pin_list->tail = page_list_prev(h.next, pin_list);
- else
- page_list_next(h.tail, pin_list)->list.prev = h.next->list.prev;
+ ASSERT(sp->u.sh.type == head_type);
+ ASSERT(!i || !sp->u.sh.head);
+ next = page_list_next(sp, pin_list);
+ page_list_del(sp, pin_list);
+ page_list_add_tail(sp, &tmp_list);
+ sp = next;
}
- h.tail->list.next = h.next->list.prev = PAGE_LIST_NULL;
-
+#ifndef PAGE_LIST_NULL
+ /* The temporary list-head is on our stack. Blank out the
+ * pointers to it in the shadows, just to get a clean failure if
+ * we accidentally follow them. */
+ tmp_list.next->prev = tmp_list.prev->next = NULL;
+#endif
+
sh_put_ref(v, smfn, 0);
}
diff --git a/xen/include/xen/mm.h b/xen/include/xen/mm.h
index 74a65a6..a62ee1e 100644
--- a/xen/include/xen/mm.h
+++ b/xen/include/xen/mm.h
@@ -172,6 +172,11 @@ page_list_first(const struct page_list_head *head)
return head->next;
}
static inline struct page_info *
+page_list_last(const struct page_list_head *head)
+{
+ return head->tail;
+}
+static inline struct page_info *
page_list_next(const struct page_info *page,
const struct page_list_head *head)
{
@@ -331,8 +336,12 @@ page_list_splice(struct page_list_head *list, struct
page_list_head *head)
# define page_list_empty list_empty
# define page_list_first(hd) list_entry((hd)->next, \
struct page_info, list)
+# define page_list_last(hd) list_entry((hd)->prev, \
+ struct page_info, list)
# define page_list_next(pg, hd) list_entry((pg)->list.next, \
struct page_info, list)
+# define page_list_prev(pg, hd) list_entry((pg)->list.prev, \
+ struct page_info, list)
# define page_list_add(pg, hd) list_add(&(pg)->list, hd)
# define page_list_add_tail(pg, hd) list_add_tail(&(pg)->list, hd)
# define page_list_del(pg, hd) list_del(&(pg)->list)
--
2.1.4
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