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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH v4] xen/domain: unify domain ID allocation
From: Denis Mukhin <dmukhin@xxxxxxxx>
Currently, hypervisor code has two different non-system domain ID allocation
algorithms:
(a) Arm port allocates IDs sequentially based on max_init_domid;
(b) x86 has another algorithm implementation embedded into
XEN_DOMCTL_createdomain; does not use max_init_domid, but does similar
thing wrt sequentially allocating IDs.
It makes sense to have a common helper code for such task across architectures
(Arm and x86).
Wrap the domain ID allocation as an arch-independent function domid_alloc() in
common/domain.c.
Allocation algorithm:
- If an explicit domain ID is provided, verify its availability and
use it if ID is unused;
- Otherwise, perform an exhaustive search starting from the end of the used
domain ID range, excluding hardware_domid.
Move the is_free_domid() helper closer to domid_alloc(). Simplify
is_free_domid() by removing the domain ID range check, as the ID is now
guaranteed to be within the valid range. Additionally, update the predicate to
return a bool value instead of an int.
No functional change intended.
Signed-off-by: Denis Mukhin <dmukhin@xxxxxxxx>
---
Changes v3->v4:
- fixed the behavior of domctl ID allocator to match the original behavior
in case of exhaustive search
- use domid_t input argument in domid_alloc()
- use DOMID_INVALID as an indicator of performing an exhaustive search
- use DOMID_INVALID as an indicator of allocator failure
- use %pd formatting for domain ID printouts in the modified code
- some comments fixups
- Link to v2:
https://lore.kernel.org/xen-devel/20250416061509.934220-1-dmukhin@xxxxxxxx/
- CI run:
https://gitlab.com/xen-project/people/dmukhin/xen/-/pipelines/1780576277
---
xen/arch/arm/dom0less-build.c | 17 ++++++------
xen/arch/arm/domain_build.c | 17 ++++++++----
xen/arch/x86/setup.c | 11 +++++---
xen/common/domain.c | 51 +++++++++++++++++++++++++++++++++++
xen/common/domctl.c | 41 +++-------------------------
xen/include/xen/domain.h | 2 ++
6 files changed, 84 insertions(+), 55 deletions(-)
diff --git a/xen/arch/arm/dom0less-build.c b/xen/arch/arm/dom0less-build.c
index a356fc94fc..61e01b7306 100644
--- a/xen/arch/arm/dom0less-build.c
+++ b/xen/arch/arm/dom0less-build.c
@@ -1038,15 +1038,13 @@ void __init create_domUs(void)
};
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");
-
if ( dt_property_read_u32(node, "capabilities", &val) )
{
if ( val & ~DOMAIN_CAPS_MASK )
@@ -1218,12 +1216,13 @@ void __init create_domUs(void)
if ( !llc_coloring_enabled && llc_colors_str )
panic("'llc-colors' found, but LLC coloring is disabled\n");
- /*
- * 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/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 270a6b97e4..fe968dd66b 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -2371,6 +2371,7 @@ 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 */
@@ -2395,19 +2396,25 @@ void __init create_dom0(void)
if ( !llc_coloring_enabled )
flags |= CDF_directmap;
- dom0 = domain_create(0, &dom0_cfg, flags);
+ domid = domid_alloc(get_initial_domain_id());
+ if ( domid == DOMID_INVALID )
+ panic("Error allocating domain ID %d\n", get_initial_domain_id());
+
+ dom0 = domain_create(domid, &dom0_cfg, flags);
if ( IS_ERR(dom0) )
- panic("Error creating domain 0 (rc = %ld)\n", PTR_ERR(dom0));
+ panic("Error creating domain %d (rc = %ld)\n", domid, PTR_ERR(dom0));
if ( llc_coloring_enabled && (rc = dom0_set_llc_colors(dom0)) )
- panic("Error initializing LLC coloring for domain 0 (rc = %d)\n", rc);
+ panic("Error initializing LLC coloring for domain %pd (rc = %d)\n",
+ dom0, rc);
if ( alloc_dom0_vcpu0(dom0) == NULL )
- panic("Error creating domain 0 vcpu0\n");
+ panic("Error creating domain %pdv0\n", dom0);
rc = construct_dom0(dom0);
if ( rc )
- panic("Could not set up DOM0 guest OS (rc = %d)\n", rc);
+ panic("Could not set up guest OS for domain %pd (rc = %d)\n",
+ dom0, rc);
set_xs_domain(dom0);
}
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 24b36c1a59..e61c023085 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -1009,8 +1009,11 @@ 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) )
@@ -1038,7 +1041,7 @@ static struct domain *__init create_dom0(struct boot_info
*bi)
if ( (strlen(acpi_param) == 0) && acpi_disabled )
{
- printk("ACPI is disabled, notifying Domain 0 (acpi=off)\n");
+ printk("ACPI is disabled, notifying domain %pd (acpi=off)\n", d);
safe_strcpy(acpi_param, "off");
}
@@ -1053,7 +1056,7 @@ static struct domain *__init create_dom0(struct boot_info
*bi)
bd->d = d;
if ( construct_dom0(bd) != 0 )
- panic("Could not construct domain 0\n");
+ panic("Could not construct domain %pd\n", d);
return d;
}
diff --git a/xen/common/domain.c b/xen/common/domain.c
index abf1969e60..7c0f7a4990 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -66,6 +66,57 @@ DEFINE_RCU_READ_LOCK(domlist_read_lock);
static struct domain *domain_hash[DOMAIN_HASH_SIZE];
struct domain *domain_list;
+/* Domain ID allocator */
+static unsigned int domid_last;
+
+static inline bool is_free_domid(domid_t dom)
+{
+ struct domain *d = rcu_lock_domain_by_id(dom);
+
+ if ( d )
+ rcu_unlock_domain(d);
+
+ return !d;
+}
+
+/*
+ * Allocate new domain ID based on the hint.
+ *
+ * If hint is outside of valid [0..DOMID_FIRST_RESERVED - 1] range of IDs,
+ * perform an exhaustive search starting from the end of the used domain ID
+ * range, excluding hardware_domid.
+ */
+domid_t domid_alloc(domid_t hint)
+{
+ domid_t domid = DOMID_INVALID;
+
+ if ( hint < DOMID_FIRST_RESERVED )
+ {
+ /* Exact match. */
+ if ( is_free_domid(hint) )
+ domid = hint;
+ }
+ else
+ {
+ for ( domid = domid_last + 1; domid != domid_last; domid++ )
+ {
+ if ( domid == DOMID_FIRST_RESERVED )
+ domid = 0;
+
+ if ( domid == hardware_domid )
+ continue;
+
+ if ( is_free_domid(domid) )
+ break;
+ }
+
+ if ( domid != domid_last )
+ domid_last = domid;
+ }
+
+ return domid;
+}
+
/*
* 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.
diff --git a/xen/common/domctl.c b/xen/common/domctl.c
index bfe2e1f9f0..2e02139660 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;
@@ -421,34 +407,15 @@ 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) )
{
ret = PTR_ERR(d);
diff --git a/xen/include/xen/domain.h b/xen/include/xen/domain.h
index e10baf2615..43e9411fc0 100644
--- a/xen/include/xen/domain.h
+++ b/xen/include/xen/domain.h
@@ -38,6 +38,8 @@ void arch_get_domain_info(const struct domain *d,
domid_t get_initial_domain_id(void);
+domid_t domid_alloc(domid_t hint);
+
/* CDF_* constant. Internal flags for domain creation. */
/* Is this a privileged domain? */
#define CDF_privileged (1U << 0)
--
2.34.1
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