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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v5 7/7] xen/arm: introduce xen-evtchn dom0less property
On Wed, 7 Sep 2022, 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>
For the DT binding:
Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> ---
> Changes in v5:
> - fix minor comments
> Changes in v4:
> - move documentation to common place for evtchn node in booting.txt
> - Add comment why we use dt_device_static_evtchn_created()
> - check if dt_get_parent() returns NULL
> - fold process_static_evtchn_node() in alloc_static_evtchn()
> 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 | 98 +++++++++++++++++
> xen/arch/arm/domain_build.c | 147 ++++++++++++++++++++++++++
> xen/arch/arm/include/asm/setup.h | 1 +
> xen/arch/arm/setup.c | 2 +
> xen/include/xen/device_tree.h | 16 +++
> 5 files changed, 264 insertions(+)
>
> diff --git a/docs/misc/arm/device-tree/booting.txt
> b/docs/misc/arm/device-tree/booting.txt
> index 47567b3906..e03e5e9e4c 100644
> --- a/docs/misc/arm/device-tree/booting.txt
> +++ b/docs/misc/arm/device-tree/booting.txt
> @@ -382,3 +382,101 @@ device-tree:
>
> This will reserve a 512MB region starting at the host physical address
> 0x30000000 to be exclusively used by DomU1.
> +
> +Static Event Channel
> +====================
> +The event channel communication will be established statically between two
> +domains (dom0 and domU also). Event channel connection information between
> +domains will be passed to Xen via the device tree node. The event channel
> +will be created and established in Xen before the domain started. The domain
> +does not need to do any operation to establish a connection. Domain only
> +needs hypercall EVTCHNOP_send(local port) to send notifications to the
> +remote guest.
> +
> +There is no need to describe the static event channel info in the domU device
> +tree. Static event channels are only useful in fully static configurations,
> +and in those configurations, the domU device tree dynamically generated by
> Xen
> +is not needed.
> +
> +To enable the event-channel interface for domU guests include the
> +xen,enhanced = "no-xenstore" property in the domU Xen device tree node.
> +
> +Under the "xen,domain" compatible node for domU, there needs to be sub-nodes
> +with compatible "xen,evtchn" that describe the event channel connection
> +between two domUs. For dom0, there needs to be sub-nodes with compatible
> +"xen,evtchn" under the chosen node.
> +
> +The static event channel 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 {
> +
> + /* One sub-node per local event channel. This sub-node is for Dom0. */
> + ec1: evtchn@1 {
> + compatible = "xen,evtchn-v1";
> + /* local-evtchn link-to-foreign-evtchn */
> + xen,evtchn = <0xa &ec2>;
> + };
> +
> + domU1 {
> + compatible = "xen,domain";
> + #address-cells = <0x2>;
> + #size-cells = <0x1>;
> + xen,enhanced = "no-xenstore";
> +
> + /* 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 {
> + compatible = "xen,domain";
> + #address-cells = <0x2>;
> + #size-cells = <0x1>;
> + xen,enhanced = "no-xenstore";
> +
> + /* 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 580ed70b9c..1a59bd7e29 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 +3054,150 @@ 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;
> + const struct dt_device_node *p1_node, *p2_node;
> + struct evtchn_alloc_unbound alloc_unbound;
> + struct evtchn_bind_interdomain bind_interdomain;
> + struct domain *d1 = NULL, *d2 = NULL;
> +
> + if ( !dt_device_is_compatible(node, "xen,evtchn-v1") )
> + return 0;
> +
> + /*
> + * Event channel is already created while parsing the other side of
> + * evtchn node.
> + */
> + if ( dt_device_static_evtchn_created(node) )
> + 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;
> + }
> +
> + p1_node = dt_get_parent(node);
> + if ( !p1_node )
> + {
> + printk(XENLOG_ERR "evtchn: evtchn parent node is NULL\n" );
> + return -EINVAL;
> + }
> +
> + p2_node = dt_get_parent(remote_node);
> + if ( !p2_node )
> + {
> + printk(XENLOG_ERR "evtchn: remote parent node is NULL\n" );
> + return -EINVAL;
> + }
> +
> + d1 = get_domain_by_id(p1_node->used_by);
> + d2 = get_domain_by_id(p2_node->used_by);
> +
> + 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 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 )
> + {
> + if ( alloc_domain_evtchn(node) != 0 )
> + panic("Could not set up domains evtchn\n");
> + }
> +
> + dt_for_each_child_node(node, evtchn_node)
> + {
> + if ( alloc_domain_evtchn(evtchn_node) != 0 )
> + panic("Could not set up domains evtchn\n");
> + }
> + }
> +}
> +
> static void __init find_gnttab_region(struct domain *d,
> struct kernel_info *kinfo)
> {
> @@ -3369,6 +3515,7 @@ 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 7814fe323d..909013992e 100644
> --- a/xen/arch/arm/setup.c
> +++ b/xen/arch/arm/setup.c
> @@ -1078,6 +1078,8 @@ 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..a28937d12a 100644
> --- a/xen/include/xen/device_tree.h
> +++ b/xen/include/xen/device_tree.h
> @@ -92,6 +92,10 @@ struct dt_device_node {
>
> /* IOMMU specific fields */
> bool is_protected;
> +
> + /* HACK: Remove this if there is a need of space */
> + bool_t static_evtchn_created;
> +
> /*
> * The main purpose of this list is to link the structure in the list
> * of devices assigned to domain.
> @@ -317,6 +321,18 @@ 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
> --
> 2.25.1
>
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