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Re: [PATCH v3 6/7] xen/arm: introduce xen-evtchn dom0less property
Hi Rahul,
On 01/09/2022 10:13, Rahul Singh wrote:
Introduce a new sub-node under /chosen node to establish static event
channel communication between domains on dom0less systems.
An event channel will be created beforehand to allow the domains to
send notifications to each other.
Signed-off-by: Rahul Singh <rahul.singh@xxxxxxx>
---
Changes in v3:
- use device-tree used_by to find the domain id of the evtchn node.
- add new static_evtchn_create variable in struct dt_device_node to
hold the information if evtchn is already created.
- fix minor comments
Changes in v2:
- no change
---
docs/misc/arm/device-tree/booting.txt | 64 ++++++++++++-
xen/arch/arm/domain_build.c | 128 ++++++++++++++++++++++++++
xen/arch/arm/include/asm/setup.h | 1 +
xen/arch/arm/setup.c | 2 +
xen/include/xen/device_tree.h | 13 +++
5 files changed, 207 insertions(+), 1 deletion(-)
diff --git a/docs/misc/arm/device-tree/booting.txt
b/docs/misc/arm/device-tree/booting.txt
index 98253414b8..edef98e6d1 100644
--- a/docs/misc/arm/device-tree/booting.txt
+++ b/docs/misc/arm/device-tree/booting.txt
@@ -212,7 +212,7 @@ with the following properties:
enable only selected interfaces.
Under the "xen,domain" compatible node, one or more sub-nodes are present
-for the DomU kernel and ramdisk.
+for the DomU kernel, ramdisk and static event channel.
The kernel sub-node has the following properties:
@@ -254,11 +254,44 @@ The ramdisk sub-node has the following properties:
property because it will be created by the UEFI stub on boot.
This option is needed only when UEFI boot is used.
+The static event channel sub-node has the following properties:
+
+- compatible
+
+ "xen,evtchn"
+
+- xen,evtchn
+
+ The property is tuples of two numbers
+ (local-evtchn link-to-foreign-evtchn) where:
+
+ local-evtchn is an integer value that will be used to allocate local port
+ for a domain to send and receive event notifications to/from the remote
+ domain. Maximum supported value is 2^17 for FIFO ABI and 4096 for 2L ABI.
+ It is recommended to use low event channel IDs.
+
+ link-to-foreign-evtchn is a single phandle to a remote evtchn to which
+ local-evtchn will be connected.
Example
=======
chosen {
+
+ module@0 {
+ compatible = "multiboot,kernel", "multiboot,module";
+ xen,uefi-binary = "...";
+ bootargs = "...";
+
+ };
NIT: Describing this node in the example seems unnecessary.
+
+ /* one sub-node per local event channel */
+ ec1: evtchn@1 {
+ compatible = "xen,evtchn-v1";
+ /* local-evtchn link-to-foreign-evtchn */
+ xen,evtchn = <0xa &ec2>;
+ };
+
Here you provide an example for dom0. But the position where you
describe the binding suggests this binding only exists for domUs.
Either we duplicate the binding or we re-order the documentation to have
common binding in a single place. My preference would be the latter.
domU1 {
compatible = "xen,domain";
#address-cells = <0x2>;
@@ -277,6 +310,23 @@ chosen {
compatible = "multiboot,ramdisk", "multiboot,module";
reg = <0x0 0x4b000000 0xffffff>;
};
+
+ /* one sub-node per local event channel */
+ ec2: evtchn@2 {
+ compatible = "xen,evtchn-v1";
+ /* local-evtchn link-to-foreign-evtchn */
+ xen,evtchn = <0xa &ec1>;
+ };
+
+ ec3: evtchn@3 {
+ compatible = "xen,evtchn-v1";
+ xen,evtchn = <0xb &ec5>;
+ };
+
+ ec4: evtchn@4 {
+ compatible = "xen,evtchn-v1";
+ xen,evtchn = <0xc &ec6>;
+ };
};
domU2 {
@@ -296,6 +346,18 @@ chosen {
compatible = "multiboot,ramdisk", "multiboot,module";
reg = <0x0 0x4d000000 0xffffff>;
};
+
+ /* one sub-node per local event channel */
+ ec5: evtchn@5 {
+ compatible = "xen,evtchn-v1";
+ /* local-evtchn link-to-foreign-evtchn */
+ xen,evtchn = <0xb &ec3>;
+ };
+
+ ec6: evtchn@6 {
+ compatible = "xen,evtchn-v1";
+ xen,evtchn = <0xd &ec4>;
+ };
};
};
diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 707e247f6a..4b24261825 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -33,6 +33,8 @@
#include <xen/grant_table.h>
#include <xen/serial.h>
+#define STATIC_EVTCHN_NODE_SIZE_CELLS 2
+
static unsigned int __initdata opt_dom0_max_vcpus;
integer_param("dom0_max_vcpus", opt_dom0_max_vcpus);
@@ -3052,6 +3054,131 @@ void __init evtchn_allocate(struct domain *d)
d->arch.hvm.params[HVM_PARAM_CALLBACK_IRQ] = val;
}
+static int __init get_evtchn_dt_property(const struct dt_device_node *np,
+ uint32_t *port, uint32_t *phandle)
+{
+ const __be32 *prop = NULL;
+ uint32_t len;
+
+ prop = dt_get_property(np, "xen,evtchn", &len);
+ if ( !prop )
+ {
+ printk(XENLOG_ERR "xen,evtchn property should not be empty.\n");
+ return -EINVAL;
+ }
+
+ if ( !len || len < dt_cells_to_size(STATIC_EVTCHN_NODE_SIZE_CELLS) )
+ {
+ printk(XENLOG_ERR "xen,evtchn property value is not valid.\n");
+ return -EINVAL;
+ }
+
+ *port = dt_next_cell(1, &prop);
+ *phandle = dt_next_cell(1, &prop);
+
+ return 0;
+}
+
+static int __init alloc_domain_evtchn(struct dt_device_node *node)
+{
+ int rc;
+ uint32_t domU1_port, domU2_port, remote_phandle;
+ struct dt_device_node *remote_node;
+ struct evtchn_alloc_unbound alloc_unbound;
+ struct evtchn_bind_interdomain bind_interdomain;
+ struct domain *d1 = NULL, *d2 = NULL;
+
+ if ( dt_device_static_evtchn_created(node) )
I think this deserve a comment explain why the node would be created.
I.e it would happen if the other side was created first. I will comment
about dt_device_static_evtchn_created() futher down.
+ return 0;
+
+ rc = get_evtchn_dt_property(node, &domU1_port, &remote_phandle);
+ if ( rc )
+ return rc;
+
+ remote_node = dt_find_node_by_phandle(remote_phandle);
+ if ( !remote_node )
+ {
+ printk(XENLOG_ERR
+ "evtchn: could not find remote evtchn phandle\n");
+ return -EINVAL;
+ }
+
+ rc = get_evtchn_dt_property(remote_node, &domU2_port, &remote_phandle);
+ if ( rc )
+ return rc;
+
+ if ( node->phandle != remote_phandle )
+ {
+ printk(XENLOG_ERR "xen,evtchn property is not setup correctly.\n");
+ return -EINVAL;
+ }
+
+ d1 = get_domain_by_id(dt_get_parent(node)->used_by);
+ d2 = get_domain_by_id(dt_get_parent(remote_node)->used_by);
I think dt_get_parent() could return NULL (i.e. for the root). So I
think you want to check that at least remote_node() has a parent. For
convenience, this check could be done in
+
+ if ( !d1 || !d2 )
+ {
+ printk(XENLOG_ERR "evtchn: could not find domains\n" );
+ return -EINVAL;
+ }
+
+ alloc_unbound.dom = d1->domain_id;
+ alloc_unbound.remote_dom = d2->domain_id;
+
+ rc = evtchn_alloc_unbound(&alloc_unbound, domU1_port);
+ if ( rc < 0 )
+ {
+ printk(XENLOG_ERR
+ "evtchn_alloc_unbound() failure (Error %d) \n", rc);
+ return rc;
+ }
+
+ bind_interdomain.remote_dom = d1->domain_id;
+ bind_interdomain.remote_port = domU1_port;
+
+ rc = evtchn_bind_interdomain(&bind_interdomain, d2, domU2_port);
+ if ( rc < 0 )
+ {
+ printk(XENLOG_ERR
+ "evtchn_bind_interdomain() failure (Error %d) \n", rc);
+ return rc;
+ }
+
+ dt_device_set_static_evtchn_created(node);
+ dt_device_set_static_evtchn_created(remote_node);
+
+ return 0;
+}
+
+void __init process_static_evtchn_node(struct dt_device_node *node)
This is missing a prototype. So I guess this wants to be static?
That said, I think it would make more sense to fold
process_static_evtchn_node() in alloc_domain_evtchn() or
alloc_static-evtchn().
+{
+ if ( dt_device_is_compatible(node, "xen,evtchn-v1") )
+ {
+ if ( alloc_domain_evtchn(node) != 0 )
+ panic("Could not set up domains evtchn\n");
+ }
+}
+
+void __init alloc_static_evtchn(void)
+{
+ struct dt_device_node *node, *evtchn_node;
+ struct dt_device_node *chosen = dt_find_node_by_path("/chosen");
+
+ BUG_ON(chosen == NULL);
+
+ if ( hardware_domain )
+ dt_device_set_used_by(chosen, hardware_domain->domain_id);
+
+ dt_for_each_child_node(chosen, node)
+ {
+ if ( hardware_domain )
+ process_static_evtchn_node(node);
+
+ dt_for_each_child_node(node, evtchn_node)
+ process_static_evtchn_node(evtchn_node);
+ }
+}
+
static void __init find_gnttab_region(struct domain *d,
struct kernel_info *kinfo)
{
@@ -3364,6 +3491,7 @@ void __init create_domUs(void)
panic("Error creating domain %s\n", dt_node_name(node));
d->is_console = true;
+ dt_device_set_used_by(node, d->domain_id);
if ( construct_domU(d, node) != 0 )
panic("Could not set up domain %s\n", dt_node_name(node));
diff --git a/xen/arch/arm/include/asm/setup.h b/xen/arch/arm/include/asm/setup.h
index 5815ccf8c5..5ee28b270f 100644
--- a/xen/arch/arm/include/asm/setup.h
+++ b/xen/arch/arm/include/asm/setup.h
@@ -106,6 +106,7 @@ int acpi_make_efi_nodes(void *fdt, struct membank
tbl_add[]);
void create_domUs(void);
void create_dom0(void);
+void alloc_static_evtchn(void);
void discard_initial_modules(void);
void fw_unreserved_regions(paddr_t s, paddr_t e,
diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
index 6e0398f3f6..cf15d359d2 100644
--- a/xen/arch/arm/setup.c
+++ b/xen/arch/arm/setup.c
@@ -1077,6 +1077,8 @@ void __init start_xen(unsigned long boot_phys_offset,
if ( acpi_disabled )
create_domUs();
+ alloc_static_evtchn();
+
/*
* This needs to be called **before** heap_init_late() so modules
* will be scrubbed (unless suppressed).
diff --git a/xen/include/xen/device_tree.h b/xen/include/xen/device_tree.h
index 430a1ef445..5579c875d2 100644
--- a/xen/include/xen/device_tree.h
+++ b/xen/include/xen/device_tree.h
@@ -82,6 +82,7 @@ struct dt_device_node {
dt_phandle phandle;
char *full_name;
domid_t used_by; /* By default it's used by dom0 */
+ bool_t static_evtchn_created;
I can see why you want to add the boolean in dt_device_node. However, I
dislike this approach because this feels an abuse of dt_device_node and
the field is only used at boot.
So this seems to be a bit of a waste to include it in the structure
(even if we are re-using padding today).
I don't have a solution that is has trivial as this approach. However,
at minimum we should document this is a HACK and should be remove if we
need space in the structure.
struct dt_property *properties;
struct dt_device_node *parent;
@@ -317,6 +318,18 @@ static inline bool_t dt_property_name_is_equal(const
struct dt_property *pp,
return !dt_prop_cmp(pp->name, name);
}
+static inline void
+dt_device_set_static_evtchn_created(struct dt_device_node *device)
+{
+ device->static_evtchn_created = true;
+}
+
+static inline bool_t
+dt_device_static_evtchn_created(const struct dt_device_node *device)
+{
+ return device->static_evtchn_created;
+}
+
/**
* dt_find_compatible_node - Find a node based on type and one of the
* tokens in its "compatible" property
Cheers,
--
Julien Grall
|
