# HG changeset patch
# User kfraser@xxxxxxxxxxxxxxxxxxxxxxxxxxx
# Node ID 66dd34f2f439e49e5a19c77ac7e7085a8b18a226
# Parent 4fc1688d9a163644b4c3b15072432d1c2b203c50
[XEN] Clean up grant-table pinning logic.
Signed-off-by: Keir Fraser <keir@xxxxxxxxxxxxx>
---
xen/common/grant_table.c | 154 +++++++++++++++++++++--------------------------
1 files changed, 70 insertions(+), 84 deletions(-)
diff -r 4fc1688d9a16 -r 66dd34f2f439 xen/common/grant_table.c
--- a/xen/common/grant_table.c Tue Sep 05 17:26:20 2006 +0100
+++ b/xen/common/grant_table.c Tue Sep 05 12:20:31 2006 -0700
@@ -90,11 +90,8 @@ __gnttab_map_grant_ref(
unsigned long frame = 0;
int rc = GNTST_okay;
struct active_grant_entry *act;
-
- /* Entry details from @rd's shared grant table. */
grant_entry_t *sha;
- domid_t sdom;
- u16 sflags;
+ union grant_combo scombo, prev_scombo, new_scombo;
/*
* We bound the number of times we retry CMPXCHG on memory locations that
@@ -175,13 +172,20 @@ __gnttab_map_grant_ref(
spin_lock(&rd->grant_table->lock);
- sdom = sha->domid;
+ /* If already pinned, check the active domid and avoid refcnt overflow. */
+ if ( act->pin &&
+ ((act->domid != ld->domain_id) ||
+ (act->pin & 0x80808080U) != 0) )
+ PIN_FAIL(unlock_out, GNTST_general_error,
+ "Bad domain (%d != %d), or risk of counter overflow %08x\n",
+ act->domid, ld->domain_id, act->pin);
if ( !act->pin ||
(!(op->flags & GNTMAP_readonly) &&
!(act->pin & (GNTPIN_hstw_mask|GNTPIN_devw_mask))) )
{
- sflags = sha->flags;
+ scombo.shorts.flags = sha->flags;
+ scombo.shorts.domid = sha->domid;
/*
* This loop attempts to set the access (reading/writing) flags
@@ -191,33 +195,29 @@ __gnttab_map_grant_ref(
*/
for ( ; ; )
{
- union grant_combo scombo, prev_scombo, new_scombo;
-
- if ( unlikely((sflags & GTF_type_mask) != GTF_permit_access) ||
- unlikely(sdom != led->domain->domain_id) )
- PIN_FAIL(unlock_out, GNTST_general_error,
- "Bad flags (%x) or dom (%d). (NB. expected dom %d)\n",
- sflags, sdom, led->domain->domain_id);
-
- /* Merge two 16-bit values into a 32-bit combined update. */
- scombo.shorts.flags = sflags;
- scombo.shorts.domid = sdom;
-
+ /* If not already pinned, check the grant domid and type. */
+ if ( !act->pin &&
+ (((scombo.shorts.flags & GTF_type_mask) !=
+ GTF_permit_access) ||
+ (scombo.shorts.domid != ld->domain_id)) )
+ PIN_FAIL(unlock_out, GNTST_general_error,
+ "Bad flags (%x) or dom (%d). (expected dom %d)\n",
+ scombo.shorts.flags, scombo.shorts.domid,
+ ld->domain_id);
+
new_scombo = scombo;
new_scombo.shorts.flags |= GTF_reading;
if ( !(op->flags & GNTMAP_readonly) )
{
new_scombo.shorts.flags |= GTF_writing;
- if ( unlikely(sflags & GTF_readonly) )
+ if ( unlikely(scombo.shorts.flags & GTF_readonly) )
PIN_FAIL(unlock_out, GNTST_general_error,
"Attempt to write-pin a r/o grant entry.\n");
}
prev_scombo.word = cmpxchg((u32 *)&sha->flags,
scombo.word, new_scombo.word);
-
- /* Did the combined update work (did we see what we expected?). */
if ( likely(prev_scombo.word == scombo.word) )
break;
@@ -225,24 +225,15 @@ __gnttab_map_grant_ref(
PIN_FAIL(unlock_out, GNTST_general_error,
"Shared grant entry is unstable.\n");
- /* Didn't see what we expected. Split out the seen flags & dom. */
- sflags = prev_scombo.shorts.flags;
- sdom = prev_scombo.shorts.domid;
+ scombo = prev_scombo;
}
if ( !act->pin )
{
- act->domid = sdom;
+ act->domid = scombo.shorts.domid;
act->frame = gmfn_to_mfn(rd, sha->frame);
}
}
- else if ( unlikely(sdom != ld->domain_id) )
- PIN_FAIL(unlock_out, GNTST_general_error,
- "Bad domain (%d). (NB. expected dom %d)\n",
- sdom, ld->domain_id);
- else if ( (act->pin & 0x80808080U) != 0 )
- PIN_FAIL(unlock_out, ENOSPC,
- "Risk of counter overflow %08x\n", act->pin);
if ( op->flags & GNTMAP_device_map )
act->pin += (op->flags & GNTMAP_readonly) ?
@@ -550,9 +541,7 @@ gnttab_prepare_for_transfer(
{
struct grant_table *rgt;
struct grant_entry *sha;
- domid_t sdom;
- u16 sflags;
- union grant_combo scombo, prev_scombo, tmp_scombo;
+ union grant_combo scombo, prev_scombo, new_scombo;
int retries = 0;
if ( unlikely((rgt = rd->grant_table) == NULL) ||
@@ -567,29 +556,25 @@ gnttab_prepare_for_transfer(
sha = &rgt->shared[ref];
- sflags = sha->flags;
- sdom = sha->domid;
+ scombo.shorts.flags = sha->flags;
+ scombo.shorts.domid = sha->domid;
for ( ; ; )
{
- if ( unlikely(sflags != GTF_accept_transfer) ||
- unlikely(sdom != ld->domain_id) )
+ if ( unlikely(scombo.shorts.flags != GTF_accept_transfer) ||
+ unlikely(scombo.shorts.domid != ld->domain_id) )
{
DPRINTK("Bad flags (%x) or dom (%d). (NB. expected dom %d)\n",
- sflags, sdom, ld->domain_id);
+ scombo.shorts.flags, scombo.shorts.domid,
+ ld->domain_id);
goto fail;
}
- /* Merge two 16-bit values into a 32-bit combined update. */
- scombo.shorts.flags = sflags;
- scombo.shorts.domid = sdom;
-
- tmp_scombo = scombo;
- tmp_scombo.shorts.flags |= GTF_transfer_committed;
+ new_scombo = scombo;
+ new_scombo.shorts.flags |= GTF_transfer_committed;
+
prev_scombo.word = cmpxchg((u32 *)&sha->flags,
- scombo.word, tmp_scombo.word);
-
- /* Did the combined update work (did we see what we expected?). */
+ scombo.word, new_scombo.word);
if ( likely(prev_scombo.word == scombo.word) )
break;
@@ -599,9 +584,7 @@ gnttab_prepare_for_transfer(
goto fail;
}
- /* Didn't see what we expected. Split out the seen flags & dom. */
- sflags = prev_scombo.shorts.flags;
- sdom = prev_scombo.shorts.domid;
+ scombo = prev_scombo;
}
spin_unlock(&rgt->lock);
@@ -739,16 +722,21 @@ __release_grant_for_copy(
gnttab_mark_dirty(rd, r_frame);
spin_lock(&rd->grant_table->lock);
+
if ( readonly )
+ {
act->pin -= GNTPIN_hstr_inc;
+ }
else
+ {
act->pin -= GNTPIN_hstw_inc;
-
- if ( !(act->pin & GNTPIN_hstw_mask) && !readonly )
- gnttab_clear_flag(_GTF_writing, &sha->flags);
+ if ( !(act->pin & (GNTPIN_devw_mask|GNTPIN_hstw_mask)) )
+ gnttab_clear_flag(_GTF_writing, &sha->flags);
+ }
if ( !act->pin )
gnttab_clear_flag(_GTF_reading, &sha->flags);
+
spin_unlock(&rd->grant_table->lock);
}
@@ -764,8 +752,7 @@ __acquire_grant_for_copy(
struct active_grant_entry *act;
s16 rc = GNTST_okay;
int retries = 0;
- u16 sflags;
- domid_t sdom;
+ union grant_combo scombo, prev_scombo, new_scombo;
if ( unlikely(gref >= NR_GRANT_ENTRIES) )
PIN_FAIL(error_out, GNTST_bad_gntref,
@@ -776,37 +763,43 @@ __acquire_grant_for_copy(
spin_lock(&rd->grant_table->lock);
- sdom = sha->domid;
+ /* If already pinned, check the active domid and avoid refcnt overflow. */
+ if ( act->pin &&
+ ((act->domid != current->domain->domain_id) ||
+ (act->pin & 0x80808080U) != 0) )
+ PIN_FAIL(unlock_out, GNTST_general_error,
+ "Bad domain (%d != %d), or risk of counter overflow %08x\n",
+ act->domid, current->domain->domain_id, act->pin);
if ( !act->pin ||
- (!readonly && !(act->pin & GNTPIN_hstw_mask)) )
- {
- sflags = sha->flags;
+ (!readonly && !(act->pin & (GNTPIN_devw_mask|GNTPIN_hstw_mask))) )
+ {
+ scombo.shorts.flags = sha->flags;
+ scombo.shorts.domid = sha->domid;
for ( ; ; )
{
- union grant_combo scombo, prev_scombo, new_scombo;
-
- if ( unlikely((sflags & GTF_type_mask) != GTF_permit_access ||
- sdom != current->domain->domain_id ) )
- PIN_FAIL(unlock_out, GNTST_general_error,
- "Bad flags (%x) or dom (%d). (NB. expected dom %d)\n",
- sflags, sdom, current->domain->domain_id);
-
- /* Merge two 16-bit values into a 32-bit combined update. */
- scombo.shorts.flags = sflags;
- scombo.shorts.domid = sdom;
-
+ /* If not already pinned, check the grant domid and type. */
+ if ( !act->pin &&
+ (((scombo.shorts.flags & GTF_type_mask) !=
+ GTF_permit_access) ||
+ (scombo.shorts.domid != current->domain->domain_id)) )
+ PIN_FAIL(unlock_out, GNTST_general_error,
+ "Bad flags (%x) or dom (%d). (expected dom %d)\n",
+ scombo.shorts.flags, scombo.shorts.domid,
+ current->domain->domain_id);
+
new_scombo = scombo;
new_scombo.shorts.flags |= GTF_reading;
if ( !readonly )
{
new_scombo.shorts.flags |= GTF_writing;
- if ( unlikely(sflags & GTF_readonly) )
+ if ( unlikely(scombo.shorts.flags & GTF_readonly) )
PIN_FAIL(unlock_out, GNTST_general_error,
"Attempt to write-pin a r/o grant entry.\n");
}
+
prev_scombo.word = cmpxchg((u32 *)&sha->flags,
scombo.word, new_scombo.word);
if ( likely(prev_scombo.word == scombo.word) )
@@ -815,23 +808,16 @@ __acquire_grant_for_copy(
if ( retries++ == 4 )
PIN_FAIL(unlock_out, GNTST_general_error,
"Shared grant entry is unstable.\n");
- sflags = prev_scombo.shorts.flags;
- sdom = prev_scombo.shorts.flags;
+
+ scombo = prev_scombo;
}
if ( !act->pin )
{
- act->domid = sdom;
+ act->domid = scombo.shorts.domid;
act->frame = gmfn_to_mfn(rd, sha->frame);
}
}
- else if ( unlikely(sdom != current->domain->domain_id) )
- PIN_FAIL(unlock_out, GNTST_general_error,
- "Bad domain (%d). (NB. expected dom %d)\n",
- sdom, current->domain->domain_id);
- else if ( (act->pin & 0x80808080U) != 0 )
- PIN_FAIL(unlock_out, ENOSPC,
- "Risk of counter overflow %08x\n", act->pin);
act->pin += readonly ? GNTPIN_hstr_inc : GNTPIN_hstw_inc;
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