From: Jan Beulich <jbeulich@suse.com>
To: "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
George Dunlap <george.dunlap@citrix.com>,
Ian Jackson <iwj@xenproject.org>, Julien Grall <julien@xen.org>,
Stefano Stabellini <sstabellini@kernel.org>, Wei Liu <wl@xen.org>
Subject: [PATCH v3] gnttab: defer allocation of status frame tracking array
Date: Thu, 15 Apr 2021 11:41:29 +0200 [thread overview]
Message-ID: <d2397cd4-040e-3cc0-22d8-3f65d01f9326@suse.com> (raw)
This array can be large when many grant frames are permitted; avoid
allocating it when it's not going to be used anyway, by doing this only
in gnttab_populate_status_frames().
Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
v3: Drop smp_wmb(). Re-base.
v2: Defer allocation to when a domain actually switches to the v2 grant
API.
--- a/xen/common/grant_table.c
+++ b/xen/common/grant_table.c
@@ -1747,6 +1747,17 @@ gnttab_populate_status_frames(struct dom
/* Make sure, prior version checks are architectural visible */
block_speculation();
+ if ( gt->status == ZERO_BLOCK_PTR )
+ {
+ gt->status = xzalloc_array(grant_status_t *,
+ grant_to_status_frames(gt->max_grant_frames));
+ if ( !gt->status )
+ {
+ gt->status = ZERO_BLOCK_PTR;
+ return -ENOMEM;
+ }
+ }
+
for ( i = nr_status_frames(gt); i < req_status_frames; i++ )
{
if ( (gt->status[i] = alloc_xenheap_page()) == NULL )
@@ -1767,18 +1778,23 @@ status_alloc_failed:
free_xenheap_page(gt->status[i]);
gt->status[i] = NULL;
}
+ if ( !nr_status_frames(gt) )
+ {
+ xfree(gt->status);
+ gt->status = ZERO_BLOCK_PTR;
+ }
return -ENOMEM;
}
static int
gnttab_unpopulate_status_frames(struct domain *d, struct grant_table *gt)
{
- unsigned int i;
+ unsigned int i, n = nr_status_frames(gt);
/* Make sure, prior version checks are architectural visible */
block_speculation();
- for ( i = 0; i < nr_status_frames(gt); i++ )
+ for ( i = 0; i < n; i++ )
{
struct page_info *pg = virt_to_page(gt->status[i]);
gfn_t gfn = gnttab_get_frame_gfn(gt, true, i);
@@ -1833,12 +1849,11 @@ gnttab_unpopulate_status_frames(struct d
page_set_owner(pg, NULL);
}
- for ( i = 0; i < nr_status_frames(gt); i++ )
- {
- free_xenheap_page(gt->status[i]);
- gt->status[i] = NULL;
- }
gt->nr_status_frames = 0;
+ for ( i = 0; i < n; i++ )
+ free_xenheap_page(gt->status[i]);
+ xfree(gt->status);
+ gt->status = ZERO_BLOCK_PTR;
return 0;
}
@@ -1969,11 +1984,11 @@ int grant_table_init(struct domain *d, i
if ( gt->shared_raw == NULL )
goto out;
- /* Status pages for grant table - for version 2 */
- gt->status = xzalloc_array(grant_status_t *,
- grant_to_status_frames(gt->max_grant_frames));
- if ( gt->status == NULL )
- goto out;
+ /*
+ * Status page tracking array for v2 gets allocated on demand. But don't
+ * leave a NULL pointer there.
+ */
+ gt->status = ZERO_BLOCK_PTR;
grant_write_lock(gt);
@@ -4047,11 +4062,12 @@ int gnttab_acquire_resource(
if ( gt->gt_version != 2 )
break;
+ rc = gnttab_get_status_frame_mfn(d, final_frame, &tmp);
+
/* Check that void ** is a suitable representation for gt->status. */
BUILD_BUG_ON(!__builtin_types_compatible_p(
typeof(gt->status), grant_status_t **));
vaddrs = (void **)gt->status;
- rc = gnttab_get_status_frame_mfn(d, final_frame, &tmp);
break;
}
next reply other threads:[~2021-04-15 9:41 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-15 9:41 Jan Beulich [this message]
2021-04-29 9:31 ` Ping: [PATCH v3] gnttab: defer allocation of status frame tracking array Jan Beulich
2021-04-29 12:53 ` Julien Grall
2021-04-29 13:15 ` Julien Grall
2021-04-29 13:40 ` Jan Beulich
2021-04-30 8:09 ` Julien Grall
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