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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH v10 1/3] xen/domain: unify domain ID allocation
From: Denis Mukhin <dmukhin@xxxxxxxx>
Currently, there are two different domain ID allocation implementations:
1) Sequential IDs allocation in dom0less Arm code based on max_init_domid;
2) Sequential IDs allocation in XEN_DOMCTL_createdomain; does not use
max_init_domid (both Arm and x86).
The domain ID allocation covers dom0 or late hwdom, predefined domains,
post-boot domains, excluding Xen system domains (domid >=
DOMID_FIRST_RESERVED).
It makes sense to have a common helper code for such task across architectures
(Arm and x86) and between dom0less / toolstack domU allocation.
Note, fixing dependency on max_init_domid is out of scope of this patch.
Wrap the domain ID allocation as an arch-independent function domid_alloc() in
common/domain.c based on the bitmap.
Allocation algorithm:
- If an explicit domain ID is provided, verify its availability and use it if
ID is not used;
- If DOMID_INVALID is provided, search the range [1..DOMID_FIRST_RESERVED-1],
starting from the last used ID. IDs are not wrapped around in dom0less case.
Implementation guarantees that two consecutive calls will never return the
same ID. ID#0 is reserved for the first boot domain (currently, dom0) and
excluded from allocation range.
Remove is_free_domid() helper as it is not needed now.
No functional change intended.
Signed-off-by: Denis Mukhin <dmukhin@xxxxxxxx>
---
Changes from v9:
- dropped unrelated message formatting from create_dom0()
- no wraparound of IDs in dom0less case
- fixed ID#0 treatment
Link to v9: https://lore.kernel.org/r/20250528225030.2652166-2-dmukhin@xxxxxxxx
---
xen/arch/arm/domain_build.c | 7 ++-
xen/arch/x86/setup.c | 7 ++-
xen/common/device-tree/dom0less-build.c | 17 +++---
xen/common/domain.c | 75 +++++++++++++++++++++++++
xen/common/domctl.c | 42 ++------------
xen/include/xen/domain.h | 3 +
6 files changed, 102 insertions(+), 49 deletions(-)
diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 4ff161887ec3..9fa5143eb98c 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -2049,6 +2049,7 @@ void __init create_dom0(void)
.grant_opts = XEN_DOMCTL_GRANT_version(opt_gnttab_max_version),
};
unsigned int flags = CDF_privileged | CDF_hardware;
+ domid_t domid;
int rc;
/* The vGIC for DOM0 is exactly emulating the hardware GIC */
@@ -2073,7 +2074,11 @@ void __init create_dom0(void)
if ( !llc_coloring_enabled )
flags |= CDF_directmap;
- dom0 = domain_create(0, &dom0_cfg, flags);
+ domid = domid_alloc(0);
+ if ( domid == DOMID_INVALID )
+ panic("Error allocating domain ID 0\n");
+
+ dom0 = domain_create(domid, &dom0_cfg, flags);
if ( IS_ERR(dom0) )
panic("Error creating domain 0 (rc = %ld)\n", PTR_ERR(dom0));
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index f32efa7c6045..7adb92d78a18 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -1044,8 +1044,11 @@ static struct domain *__init create_dom0(struct
boot_info *bi)
if ( iommu_enabled )
dom0_cfg.flags |= XEN_DOMCTL_CDF_iommu;
- /* Create initial domain. Not d0 for pvshim. */
- bd->domid = get_initial_domain_id();
+ /* Allocate initial domain ID. Not d0 for pvshim. */
+ bd->domid = domid_alloc(get_initial_domain_id());
+ if ( bd->domid == DOMID_INVALID )
+ panic("Error allocating domain ID %d\n", get_initial_domain_id());
+
d = domain_create(bd->domid, &dom0_cfg,
pv_shim ? 0 : CDF_privileged | CDF_hardware);
if ( IS_ERR(d) )
diff --git a/xen/common/device-tree/dom0less-build.c
b/xen/common/device-tree/dom0less-build.c
index 3d503c697337..576fdfa6a19a 100644
--- a/xen/common/device-tree/dom0less-build.c
+++ b/xen/common/device-tree/dom0less-build.c
@@ -839,15 +839,13 @@ void __init create_domUs(void)
struct xen_domctl_createdomain d_cfg = {0};
unsigned int flags = 0U;
bool has_dtb = false;
+ domid_t domid;
uint32_t val;
int rc;
if ( !dt_device_is_compatible(node, "xen,domain") )
continue;
- if ( (max_init_domid + 1) >= DOMID_FIRST_RESERVED )
- panic("No more domain IDs available\n");
-
d_cfg.max_evtchn_port = 1023;
d_cfg.max_grant_frames = -1;
d_cfg.max_maptrack_frames = -1;
@@ -965,12 +963,13 @@ void __init create_domUs(void)
arch_create_domUs(node, &d_cfg, flags);
- /*
- * The variable max_init_domid is initialized with zero, so here it's
- * very important to use the pre-increment operator to call
- * domain_create() with a domid > 0. (domid == 0 is reserved for Dom0)
- */
- d = domain_create(++max_init_domid, &d_cfg, flags);
+ domid = domid_alloc(DOMID_INVALID);
+ if ( domid == DOMID_INVALID )
+ panic("Error allocating ID for domain %s\n", dt_node_name(node));
+ if ( max_init_domid < domid )
+ max_init_domid = domid;
+
+ d = domain_create(domid, &d_cfg, flags);
if ( IS_ERR(d) )
panic("Error creating domain %s (rc = %ld)\n",
dt_node_name(node), PTR_ERR(d));
diff --git a/xen/common/domain.c b/xen/common/domain.c
index 434d32901b1b..be022c720b13 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -66,6 +66,14 @@ DEFINE_RCU_READ_LOCK(domlist_read_lock);
static struct domain *domain_hash[DOMAIN_HASH_SIZE];
struct domain *domain_list;
+/*
+ * Domain ID allocator.
+ * Covers dom0 or late hwdom, predefined domains, post-boot domains; excludes
+ * Xen system domains (ID >= DOMID_FIRST_RESERVED).
+ */
+static DEFINE_SPINLOCK(domid_lock);
+static DECLARE_BITMAP(domid_bitmap, DOMID_FIRST_RESERVED);
+
/*
* Insert a domain into the domlist/hash. This allows the domain to be looked
* up by domid, and therefore to be the subject of hypercalls/etc.
@@ -1452,6 +1460,8 @@ void domain_destroy(struct domain *d)
TRACE_TIME(TRC_DOM0_DOM_REM, d->domain_id);
+ domid_free(d->domain_id);
+
/* Remove from the domlist/hash. */
domlist_remove(d);
@@ -2433,6 +2443,71 @@ void thaw_domains(void)
rcu_read_unlock(&domlist_read_lock);
}
+domid_t domid_alloc(domid_t domid)
+{
+ static domid_t domid_last;
+
+ spin_lock(&domid_lock);
+
+ /* Exact match. */
+ if ( domid < DOMID_FIRST_RESERVED )
+ {
+ if ( __test_and_set_bit(domid, domid_bitmap) )
+ domid = DOMID_INVALID;
+ }
+ /*
+ * Exhaustive search.
+ *
+ * Domain ID#0 is reserved for the first boot domain (e.g. control domain)
+ * and excluded from allocation.
+ *
+ * In dom0less build, domains are not dynamically destroyed, so there's no
+ * need to do a wraparound of the IDs.
+ */
+#ifdef CONFIG_DOM0LESS_BOOT
+ else if ( domid_last + 1 >= DOMID_FIRST_RESERVED )
+ {
+ domid = DOMID_INVALID;
+ }
+#endif
+ else
+ {
+ domid = find_next_zero_bit(domid_bitmap,
+ DOMID_FIRST_RESERVED,
+ domid_last + 1);
+#ifdef CONFIG_DOM0LESS_BOOT
+ if ( domid == DOMID_FIRST_RESERVED )
+ domid = find_next_zero_bit(domid_bitmap,
+ DOMID_FIRST_RESERVED,
+ 1);
+#endif
+
+ if ( domid < DOMID_FIRST_RESERVED )
+ {
+ __set_bit(domid, domid_bitmap);
+ domid_last = domid;
+ }
+ else
+ {
+ domid = DOMID_INVALID;
+ }
+ }
+
+ spin_unlock(&domid_lock);
+
+ return domid;
+}
+
+void domid_free(domid_t domid)
+{
+ if ( domid < DOMID_FIRST_RESERVED )
+ {
+ spin_lock(&domid_lock);
+ __clear_bit(domid, domid_bitmap);
+ spin_unlock(&domid_lock);
+ }
+}
+
/*
* Local variables:
* mode: C
diff --git a/xen/common/domctl.c b/xen/common/domctl.c
index bfe2e1f9f057..8ef0c147c9b0 100644
--- a/xen/common/domctl.c
+++ b/xen/common/domctl.c
@@ -49,20 +49,6 @@ static int xenctl_bitmap_to_nodemask(nodemask_t *nodemask,
MAX_NUMNODES);
}
-static inline int is_free_domid(domid_t dom)
-{
- struct domain *d;
-
- if ( dom >= DOMID_FIRST_RESERVED )
- return 0;
-
- if ( (d = rcu_lock_domain_by_id(dom)) == NULL )
- return 1;
-
- rcu_unlock_domain(d);
- return 0;
-}
-
void getdomaininfo(struct domain *d, struct xen_domctl_getdomaininfo *info)
{
struct vcpu *v;
@@ -421,36 +407,18 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t)
u_domctl)
case XEN_DOMCTL_createdomain:
{
- domid_t dom;
- static domid_t rover = 0;
+ domid_t domid = domid_alloc(op->domain);
- dom = op->domain;
- if ( (dom > 0) && (dom < DOMID_FIRST_RESERVED) )
+ if ( domid == DOMID_INVALID )
{
ret = -EEXIST;
- if ( !is_free_domid(dom) )
- break;
- }
- else
- {
- for ( dom = rover + 1; dom != rover; dom++ )
- {
- if ( dom == DOMID_FIRST_RESERVED )
- dom = 1;
- if ( is_free_domid(dom) )
- break;
- }
-
- ret = -ENOMEM;
- if ( dom == rover )
- break;
-
- rover = dom;
+ break;
}
- d = domain_create(dom, &op->u.createdomain, false);
+ d = domain_create(domid, &op->u.createdomain, false);
if ( IS_ERR(d) )
{
+ domid_free(domid);
ret = PTR_ERR(d);
d = NULL;
break;
diff --git a/xen/include/xen/domain.h b/xen/include/xen/domain.h
index e10baf2615fd..8aab05ae93c8 100644
--- a/xen/include/xen/domain.h
+++ b/xen/include/xen/domain.h
@@ -38,6 +38,9 @@ void arch_get_domain_info(const struct domain *d,
domid_t get_initial_domain_id(void);
+domid_t domid_alloc(domid_t domid);
+void domid_free(domid_t domid);
+
/* CDF_* constant. Internal flags for domain creation. */
/* Is this a privileged domain? */
#define CDF_privileged (1U << 0)
--
2.34.1
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