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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH v2 2/2] gnttab: consolidate pin-to-status syncing
Forever since the fix for XSA-230 the 2nd of the comments ahead of
fixup_status_for_copy_pin() has been stale - there's nothing specific to
transitive grants there anymore.
Move the function up, drop the "copy" part from its name again, add a
"readonly" parameter, and use it also on other paths having decremented
one (or not having got to increment any) of the pin counts.
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
v2: Rename helper to reduce_status_for_pin() and adjust its comment
accordingly.
--- a/xen/common/grant_table.c
+++ b/xen/common/grant_table.c
@@ -920,6 +920,25 @@ static int _set_status(const grant_entry
return _set_status_v2(shah, status, rd, act, readonly, mapflag,
ldomid);
}
+/*
+ * The status for a grant may indicate that we're taking more access than
+ * the pin requires. Reduce the status to match the pin. Called with the
+ * domain's grant table lock held at least in read mode and with the active
+ * entry lock held (iow act->pin can't change behind our backs).
+ */
+static void reduce_status_for_pin(struct domain *rd,
+ const struct active_grant_entry *act,
+ uint16_t *status, bool readonly)
+{
+ unsigned int clear_flags = act->pin ? 0 : GTF_reading;
+
+ if ( !readonly && !(act->pin & (GNTPIN_hstw_mask | GNTPIN_devw_mask)) )
+ clear_flags |= GTF_writing;
+
+ if ( clear_flags )
+ gnttab_clear_flags(rd, clear_flags, status);
+}
+
static struct active_grant_entry *grant_map_exists(const struct domain *ld,
struct grant_table *rgt,
mfn_t mfn,
@@ -1003,8 +1022,7 @@ map_grant_ref(
mfn_t mfn;
struct page_info *pg = NULL;
int rc = GNTST_okay;
- unsigned int cache_flags, clear_flags = 0, refcnt = 0, typecnt = 0,
- pin_incr = 0;
+ unsigned int cache_flags, refcnt = 0, typecnt = 0, pin_incr = 0;
bool host_map_created = false;
struct active_grant_entry *act = NULL;
struct grant_mapping *mt;
@@ -1296,15 +1314,7 @@ map_grant_ref(
act->pin -= pin_incr;
unlock_out_clear:
- if ( !(op->flags & GNTMAP_readonly) &&
- !(act->pin & (GNTPIN_hstw_mask|GNTPIN_devw_mask)) )
- clear_flags |= GTF_writing;
-
- if ( !act->pin )
- clear_flags |= GTF_reading;
-
- if ( clear_flags )
- gnttab_clear_flags(rd, clear_flags, status);
+ reduce_status_for_pin(rd, act, status, op->flags & GNTMAP_readonly);
act_release_out:
active_entry_release(act);
@@ -1519,7 +1529,6 @@ unmap_common_complete(struct gnttab_unma
grant_entry_header_t *sha;
struct page_info *pg;
uint16_t *status;
- unsigned int clear_flags = 0;
if ( evaluate_nospec(!op->done) )
{
@@ -1578,15 +1587,7 @@ unmap_common_complete(struct gnttab_unma
act->pin -= GNTPIN_hstw_inc;
}
- if ( ((act->pin & (GNTPIN_devw_mask|GNTPIN_hstw_mask)) == 0) &&
- !(op->done & GNTMAP_readonly) )
- clear_flags |= GTF_writing;
-
- if ( act->pin == 0 )
- clear_flags |= GTF_reading;
-
- if ( clear_flags )
- gnttab_clear_flags(rd, clear_flags, status);
+ reduce_status_for_pin(rd, act, status, op->done & GNTMAP_readonly);
active_entry_release(act);
grant_read_unlock(rgt);
@@ -2426,7 +2427,6 @@ release_grant_for_copy(
uint16_t *status;
grant_ref_t trans_gref;
struct domain *td;
- unsigned int clear_flags = 0;
grant_read_lock(rgt);
@@ -2456,15 +2456,9 @@ release_grant_for_copy(
gnttab_mark_dirty(rd, mfn);
act->pin -= GNTPIN_hstw_inc;
- if ( !(act->pin & (GNTPIN_devw_mask|GNTPIN_hstw_mask)) )
- clear_flags |= GTF_writing;
}
- if ( !act->pin )
- clear_flags |= GTF_reading;
-
- if ( clear_flags )
- gnttab_clear_flags(rd, clear_flags, status);
+ reduce_status_for_pin(rd, act, status, readonly);
active_entry_release(act);
grant_read_unlock(rgt);
@@ -2481,27 +2475,6 @@ release_grant_for_copy(
}
}
-/* The status for a grant indicates that we're taking more access than
- the pin requires. Fix up the status to match the pin. Called
- under the domain's grant table lock. */
-/* Only safe on transitive grants. Even then, note that we don't
- attempt to drop any pin on the referent grant. */
-static void fixup_status_for_copy_pin(struct domain *rd,
- const struct active_grant_entry *act,
- uint16_t *status)
-{
- unsigned int clear_flags = 0;
-
- if ( !(act->pin & (GNTPIN_hstw_mask | GNTPIN_devw_mask)) )
- clear_flags |= GTF_writing;
-
- if ( !act->pin )
- clear_flags |= GTF_reading;
-
- if ( clear_flags )
- gnttab_clear_flags(rd, clear_flags, status);
-}
-
/*
* Grab a machine frame number from a grant entry and update the flags
* and pin count as appropriate. If rc == GNTST_okay, note that this *does*
@@ -2529,7 +2502,6 @@ acquire_grant_for_copy(
bool is_sub_page;
s16 rc = GNTST_okay;
unsigned int pin_incr = readonly ? GNTPIN_hstr_inc : GNTPIN_hstw_inc;
- unsigned int clear_flags = 0;
*page = NULL;
@@ -2616,8 +2588,8 @@ acquire_grant_for_copy(
if ( rc != GNTST_okay )
{
- fixup_status_for_copy_pin(rd, act, status);
rcu_unlock_domain(td);
+ reduce_status_for_pin(rd, act, status, readonly);
active_entry_release(act);
grant_read_unlock(rgt);
return rc;
@@ -2639,8 +2611,8 @@ acquire_grant_for_copy(
!act->is_sub_page)) )
{
release_grant_for_copy(td, trans_gref, readonly);
- fixup_status_for_copy_pin(rd, act, status);
rcu_unlock_domain(td);
+ reduce_status_for_pin(rd, act, status, readonly);
active_entry_release(act);
grant_read_unlock(rgt);
put_page(*page);
@@ -2754,15 +2726,7 @@ acquire_grant_for_copy(
return rc;
unlock_out_clear:
- if ( !(readonly) &&
- !(act->pin & (GNTPIN_hstw_mask | GNTPIN_devw_mask)) )
- clear_flags |= GTF_writing;
-
- if ( !act->pin )
- clear_flags |= GTF_reading;
-
- if ( clear_flags )
- gnttab_clear_flags(rd, clear_flags, status);
+ reduce_status_for_pin(rd, act, status, readonly);
unlock_out:
active_entry_release(act);
@@ -3732,8 +3696,6 @@ gnttab_release_mappings(
for ( handle = 0; handle < gt->maptrack_limit; handle++ )
{
- unsigned int clear_flags = 0;
-
map = &maptrack_entry(gt, handle);
if ( !(map->flags & (GNTMAP_device_map|GNTMAP_host_map)) )
continue;
@@ -3806,16 +3768,9 @@ gnttab_release_mappings(
put_page(pg);
}
}
-
- if ( (act->pin & (GNTPIN_devw_mask|GNTPIN_hstw_mask)) == 0 )
- clear_flags |= GTF_writing;
}
- if ( act->pin == 0 )
- clear_flags |= GTF_reading;
-
- if ( clear_flags )
- gnttab_clear_flags(rd, clear_flags, status);
+ reduce_status_for_pin(rd, act, status, map->flags & GNTMAP_readonly);
active_entry_release(act);
grant_read_unlock(rgt);
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