Mailing List Archive

commit 01a8a51412343b8243403bbbaf0859db9a1edfab
Author: Tamas K Lengyel <tamas.lengyel@intel.com>
AuthorDate: Wed Sep 22 16:17:54 2021 +0200
Commit: Jan Beulich <jbeulich@suse.com>
CommitDate: Wed Sep 22 16:17:54 2021 +0200

x86/mem_sharing: don't lock parent during fork reset

During fork reset operation the parent domain doesn't need to be gathered using
rcu_lock_live_remote_domain_by_id, the fork already has the parent pointer.

Signed-off-by: Tamas K Lengyel <tamas.lengyel@intel.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
---
xen/arch/x86/mm/mem_sharing.c | 15 ++++-----------
1 file changed, 4 insertions(+), 11 deletions(-)

diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c
index 8d5d44bdbc..74d2869c0e 100644
--- a/xen/arch/x86/mm/mem_sharing.c
+++ b/xen/arch/x86/mm/mem_sharing.c
@@ -1861,9 +1861,9 @@ static int fork(struct domain *cd, struct domain *d)
done:
if ( rc && rc != -ERESTART )
{
+ cd->parent = NULL;
domain_unpause(d);
put_domain(d);
- cd->parent = NULL;
}

return rc;
@@ -1879,9 +1879,10 @@ static int fork(struct domain *cd, struct domain *d)
* footprints the hypercall continuation should be implemented (or if this
* feature needs to be become "stable").
*/
-static int mem_sharing_fork_reset(struct domain *d, struct domain *pd)
+static int mem_sharing_fork_reset(struct domain *d)
{
int rc;
+ struct domain *pd = d->parent;
struct p2m_domain *p2m = p2m_get_hostp2m(d);
struct page_info *page, *tmp;

@@ -2226,8 +2227,6 @@ int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg)

case XENMEM_sharing_op_fork_reset:
{
- struct domain *pd;
-
rc = -EINVAL;
if ( mso.u.fork.pad || mso.u.fork.flags )
goto out;
@@ -2236,13 +2235,7 @@ int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg)
if ( !d->parent )
goto out;

- rc = rcu_lock_live_remote_domain_by_id(d->parent->domain_id, &pd);
- if ( rc )
- goto out;
-
- rc = mem_sharing_fork_reset(d, pd);
-
- rcu_unlock_domain(pd);
+ rc = mem_sharing_fork_reset(d);
break;
}

--
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