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Date: Thu, 23 Jan 2014 21:23:44 +0000
From: Zoltan Kiss <zoltan.kiss@...rix.com>
To: <ian.campbell@...rix.com>, <wei.liu2@...rix.com>,
<xen-devel@...ts.xenproject.org>, <netdev@...r.kernel.org>,
<linux-kernel@...r.kernel.org>, <jonathan.davies@...rix.com>
CC: Zoltan Kiss <zoltan.kiss@...rix.com>
Subject: [PATCH v6] xen/grant-table: Avoid m2p_override during mapping
The grant mapping API does m2p_override unnecessarily: only gntdev needs it,
for blkback and future netback patches it just cause a lock contention, as
those pages never go to userspace. Therefore this series does the following:
- the original functions were renamed to __gnttab_[un]map_refs, with a new
parameter m2p_override
- based on m2p_override either they follow the original behaviour, or just set
the private flag and call set_phys_to_machine
- gnttab_[un]map_refs are now a wrapper to call __gnttab_[un]map_refs with
m2p_override false
- a new function gnttab_[un]map_refs_userspace provides the old behaviour
It also removes a stray space from page.h and change ret to 0 if
XENFEAT_auto_translated_physmap, as that is the only possible return value
there.
v2:
- move the storing of the old mfn in page->index to gnttab_map_refs
- move the function header update to a separate patch
v3:
- a new approach to retain old behaviour where it needed
- squash the patches into one
v4:
- move out the common bits from m2p* functions, and pass pfn/mfn as parameter
- clear page->private before doing anything with the page, so m2p_find_override
won't race with this
v5:
- change return value handling in __gnttab_[un]map_refs
- remove a stray space in page.h
- add detail why ret = 0 now at some places
v6:
- don't pass pfn to m2p* functions, just get it locally
Signed-off-by: Zoltan Kiss <zoltan.kiss@...rix.com>
Suggested-by: David Vrabel <david.vrabel@...rix.com>
---
arch/x86/include/asm/xen/page.h | 5 +-
arch/x86/xen/p2m.c | 17 +------
drivers/block/xen-blkback/blkback.c | 15 +++---
drivers/xen/gntdev.c | 13 +++--
drivers/xen/grant-table.c | 89 ++++++++++++++++++++++++++++++-----
include/xen/grant_table.h | 8 +++-
6 files changed, 101 insertions(+), 46 deletions(-)
diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
index b913915..ce47243 100644
--- a/arch/x86/include/asm/xen/page.h
+++ b/arch/x86/include/asm/xen/page.h
@@ -52,7 +52,8 @@ extern unsigned long set_phys_range_identity(unsigned long pfn_s,
extern int m2p_add_override(unsigned long mfn, struct page *page,
struct gnttab_map_grant_ref *kmap_op);
extern int m2p_remove_override(struct page *page,
- struct gnttab_map_grant_ref *kmap_op);
+ struct gnttab_map_grant_ref *kmap_op,
+ unsigned long mfn);
extern struct page *m2p_find_override(unsigned long mfn);
extern unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn);
@@ -121,7 +122,7 @@ static inline unsigned long mfn_to_pfn(unsigned long mfn)
pfn = m2p_find_override_pfn(mfn, ~0);
}
- /*
+ /*
* pfn is ~0 if there are no entries in the m2p for mfn or if the
* entry doesn't map back to the mfn and m2p_override doesn't have a
* valid entry for it.
diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 2ae8699..bd4724b 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -888,13 +888,6 @@ int m2p_add_override(unsigned long mfn, struct page *page,
"m2p_add_override: pfn %lx not mapped", pfn))
return -EINVAL;
}
- WARN_ON(PagePrivate(page));
- SetPagePrivate(page);
- set_page_private(page, mfn);
- page->index = pfn_to_mfn(pfn);
-
- if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn))))
- return -ENOMEM;
if (kmap_op != NULL) {
if (!PageHighMem(page)) {
@@ -933,19 +926,16 @@ int m2p_add_override(unsigned long mfn, struct page *page,
}
EXPORT_SYMBOL_GPL(m2p_add_override);
int m2p_remove_override(struct page *page,
- struct gnttab_map_grant_ref *kmap_op)
+ struct gnttab_map_grant_ref *kmap_op,
+ unsigned long mfn)
{
unsigned long flags;
- unsigned long mfn;
unsigned long pfn;
unsigned long uninitialized_var(address);
unsigned level;
pte_t *ptep = NULL;
pfn = page_to_pfn(page);
- mfn = get_phys_to_machine(pfn);
- if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT))
- return -EINVAL;
if (!PageHighMem(page)) {
address = (unsigned long)__va(pfn << PAGE_SHIFT);
@@ -959,10 +949,7 @@ int m2p_remove_override(struct page *page,
spin_lock_irqsave(&m2p_override_lock, flags);
list_del(&page->lru);
spin_unlock_irqrestore(&m2p_override_lock, flags);
- WARN_ON(!PagePrivate(page));
- ClearPagePrivate(page);
- set_phys_to_machine(pfn, page->index);
if (kmap_op != NULL) {
if (!PageHighMem(page)) {
struct multicall_space mcs;
diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index 6620b73..875025f 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -285,8 +285,7 @@ static void free_persistent_gnts(struct xen_blkif *blkif, struct rb_root *root,
if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST ||
!rb_next(&persistent_gnt->node)) {
- ret = gnttab_unmap_refs(unmap, NULL, pages,
- segs_to_unmap);
+ ret = gnttab_unmap_refs(unmap, pages, segs_to_unmap);
BUG_ON(ret);
put_free_pages(blkif, pages, segs_to_unmap);
segs_to_unmap = 0;
@@ -321,8 +320,7 @@ static void unmap_purged_grants(struct work_struct *work)
pages[segs_to_unmap] = persistent_gnt->page;
if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST) {
- ret = gnttab_unmap_refs(unmap, NULL, pages,
- segs_to_unmap);
+ ret = gnttab_unmap_refs(unmap, pages, segs_to_unmap);
BUG_ON(ret);
put_free_pages(blkif, pages, segs_to_unmap);
segs_to_unmap = 0;
@@ -330,7 +328,7 @@ static void unmap_purged_grants(struct work_struct *work)
kfree(persistent_gnt);
}
if (segs_to_unmap > 0) {
- ret = gnttab_unmap_refs(unmap, NULL, pages, segs_to_unmap);
+ ret = gnttab_unmap_refs(unmap, pages, segs_to_unmap);
BUG_ON(ret);
put_free_pages(blkif, pages, segs_to_unmap);
}
@@ -670,15 +668,14 @@ static void xen_blkbk_unmap(struct xen_blkif *blkif,
GNTMAP_host_map, pages[i]->handle);
pages[i]->handle = BLKBACK_INVALID_HANDLE;
if (++invcount == BLKIF_MAX_SEGMENTS_PER_REQUEST) {
- ret = gnttab_unmap_refs(unmap, NULL, unmap_pages,
- invcount);
+ ret = gnttab_unmap_refs(unmap, unmap_pages, invcount);
BUG_ON(ret);
put_free_pages(blkif, unmap_pages, invcount);
invcount = 0;
}
}
if (invcount) {
- ret = gnttab_unmap_refs(unmap, NULL, unmap_pages, invcount);
+ ret = gnttab_unmap_refs(unmap, unmap_pages, invcount);
BUG_ON(ret);
put_free_pages(blkif, unmap_pages, invcount);
}
@@ -740,7 +737,7 @@ again:
}
if (segs_to_map) {
- ret = gnttab_map_refs(map, NULL, pages_to_gnt, segs_to_map);
+ ret = gnttab_map_refs(map, pages_to_gnt, segs_to_map);
BUG_ON(ret);
}
diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index e41c79c..e652c0e 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -284,8 +284,10 @@ static int map_grant_pages(struct grant_map *map)
}
pr_debug("map %d+%d\n", map->index, map->count);
- err = gnttab_map_refs(map->map_ops, use_ptemod ? map->kmap_ops : NULL,
- map->pages, map->count);
+ err = gnttab_map_refs_userspace(map->map_ops,
+ use_ptemod ? map->kmap_ops : NULL,
+ map->pages,
+ map->count);
if (err)
return err;
@@ -315,9 +317,10 @@ static int __unmap_grant_pages(struct grant_map *map, int offset, int pages)
}
}
- err = gnttab_unmap_refs(map->unmap_ops + offset,
- use_ptemod ? map->kmap_ops + offset : NULL, map->pages + offset,
- pages);
+ err = gnttab_unmap_refs_userspace(map->unmap_ops + offset,
+ use_ptemod ? map->kmap_ops + offset : NULL,
+ map->pages + offset,
+ pages);
if (err)
return err;
diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index aa846a4..e4ddfeb 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -880,15 +880,17 @@ void gnttab_batch_copy(struct gnttab_copy *batch, unsigned count)
}
EXPORT_SYMBOL_GPL(gnttab_batch_copy);
-int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
+int __gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
struct gnttab_map_grant_ref *kmap_ops,
- struct page **pages, unsigned int count)
+ struct page **pages, unsigned int count,
+ bool m2p_override)
{
int i, ret;
bool lazy = false;
pte_t *pte;
- unsigned long mfn;
+ unsigned long mfn, pfn;
+ BUG_ON(kmap_ops && !m2p_override);
ret = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, map_ops, count);
if (ret)
return ret;
@@ -907,10 +909,12 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
set_phys_to_machine(map_ops[i].host_addr >> PAGE_SHIFT,
map_ops[i].dev_bus_addr >> PAGE_SHIFT);
}
- return ret;
+ return 0;
}
- if (!in_interrupt() && paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
+ if (m2p_override &&
+ !in_interrupt() &&
+ paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
arch_enter_lazy_mmu_mode();
lazy = true;
}
@@ -927,8 +931,20 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
} else {
mfn = PFN_DOWN(map_ops[i].dev_bus_addr);
}
- ret = m2p_add_override(mfn, pages[i], kmap_ops ?
- &kmap_ops[i] : NULL);
+ pfn = page_to_pfn(pages[i]);
+
+ WARN_ON(PagePrivate(pages[i]));
+ SetPagePrivate(pages[i]);
+ set_page_private(pages[i], mfn);
+
+ pages[i]->index = pfn_to_mfn(pfn);
+ if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)))) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ if (m2p_override)
+ ret = m2p_add_override(mfn, pages[i], kmap_ops ?
+ &kmap_ops[i] : NULL);
if (ret)
goto out;
}
@@ -939,15 +955,32 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
return ret;
}
+
+int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
+ struct page **pages, unsigned int count)
+{
+ return __gnttab_map_refs(map_ops, NULL, pages, count, false);
+}
EXPORT_SYMBOL_GPL(gnttab_map_refs);
-int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
+int gnttab_map_refs_userspace(struct gnttab_map_grant_ref *map_ops,
+ struct gnttab_map_grant_ref *kmap_ops,
+ struct page **pages, unsigned int count)
+{
+ return __gnttab_map_refs(map_ops, kmap_ops, pages, count, true);
+}
+EXPORT_SYMBOL_GPL(gnttab_map_refs_userspace);
+
+int __gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
struct gnttab_map_grant_ref *kmap_ops,
- struct page **pages, unsigned int count)
+ struct page **pages, unsigned int count,
+ bool m2p_override)
{
int i, ret;
bool lazy = false;
+ unsigned long pfn, mfn;
+ BUG_ON(kmap_ops && !m2p_override);
ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap_ops, count);
if (ret)
return ret;
@@ -958,17 +991,33 @@ int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
set_phys_to_machine(unmap_ops[i].host_addr >> PAGE_SHIFT,
INVALID_P2M_ENTRY);
}
- return ret;
+ return 0;
}
- if (!in_interrupt() && paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
+ if (m2p_override &&
+ !in_interrupt() &&
+ paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
arch_enter_lazy_mmu_mode();
lazy = true;
}
for (i = 0; i < count; i++) {
- ret = m2p_remove_override(pages[i], kmap_ops ?
- &kmap_ops[i] : NULL);
+ pfn = page_to_pfn(pages[i]);
+ mfn = get_phys_to_machine(pfn);
+ if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT)) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ set_page_private(pages[i], INVALID_P2M_ENTRY);
+ WARN_ON(!PagePrivate(pages[i]));
+ ClearPagePrivate(pages[i]);
+ set_phys_to_machine(pfn, pages[i]->index);
+ if (m2p_override)
+ ret = m2p_remove_override(pages[i],
+ kmap_ops ?
+ &kmap_ops[i] : NULL,
+ mfn);
if (ret)
goto out;
}
@@ -979,8 +1028,22 @@ int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
return ret;
}
+
+int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *map_ops,
+ struct page **pages, unsigned int count)
+{
+ return __gnttab_unmap_refs(map_ops, NULL, pages, count, false);
+}
EXPORT_SYMBOL_GPL(gnttab_unmap_refs);
+int gnttab_unmap_refs_userspace(struct gnttab_unmap_grant_ref *map_ops,
+ struct gnttab_map_grant_ref *kmap_ops,
+ struct page **pages, unsigned int count)
+{
+ return __gnttab_unmap_refs(map_ops, kmap_ops, pages, count, true);
+}
+EXPORT_SYMBOL_GPL(gnttab_unmap_refs_userspace);
+
static unsigned nr_status_frames(unsigned nr_grant_frames)
{
BUG_ON(grefs_per_grant_frame == 0);
diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h
index 694dcaf..9a919b1 100644
--- a/include/xen/grant_table.h
+++ b/include/xen/grant_table.h
@@ -184,11 +184,15 @@ unsigned int gnttab_max_grant_frames(void);
#define gnttab_map_vaddr(map) ((void *)(map.host_virt_addr))
int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
- struct gnttab_map_grant_ref *kmap_ops,
struct page **pages, unsigned int count);
+int gnttab_map_refs_userspace(struct gnttab_map_grant_ref *map_ops,
+ struct gnttab_map_grant_ref *kmap_ops,
+ struct page **pages, unsigned int count);
int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
- struct gnttab_map_grant_ref *kunmap_ops,
struct page **pages, unsigned int count);
+int gnttab_unmap_refs_userspace(struct gnttab_unmap_grant_ref *unmap_ops,
+ struct gnttab_map_grant_ref *kunmap_ops,
+ struct page **pages, unsigned int count);
/* Perform a batch of grant map/copy operations. Retry every batch slot
* for which the hypervisor returns GNTST_eagain. This is typically due
--
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