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xen/xenbus: report a ring's host node only when Xen resolved it #109

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xen/xenbus: report a ring's host node only when Xen resolved it #109

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33 changes: 23 additions & 10 deletions drivers/xen/xenbus/xenbus_client.c
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Original file line number Diff line number Diff line change
Expand Up @@ -67,6 +67,10 @@ struct xenbus_map_node {
struct page *pages[XENBUS_MAX_RING_PAGES];
unsigned long addrs[XENBUS_MAX_RING_GRANTS];
void *addr;
/* Host node of the foreign frames; NUMA_NO_NODE if Xen
* did not say.
*/
int host_node;
} hvm;
};
grant_handle_t handles[XENBUS_MAX_RING_GRANTS];
Expand Down Expand Up @@ -868,6 +872,7 @@ static int xenbus_map_ring_hvm(struct xenbus_device *dev,
}

node->hvm.addr = addr;
node->hvm.host_node = host_node;

spin_lock(&xenbus_valloc_lock);
list_add(&node->next, &xenbus_valloc_pages);
Expand Down Expand Up @@ -912,24 +917,32 @@ EXPORT_SYMBOL_GPL(xenbus_unmap_ring_vfree);

int xenbus_ring_host_node(struct xenbus_device *dev, void *vaddr)
{
struct page *page;
struct xenbus_map_node *node;
int host_node = NUMA_NO_NODE;

/*
* PV mappings install foreign MFNs directly in the PTEs and have
* no struct page in dom0's mem_map for the foreign frame. PVH
* dom0 keeps a placeholder struct page (allocated from the
* matching per-node pool of xen_alloc_unpopulated_pages_node)
* whose page_to_nid() reports the host node of the foreign frame
* by construction.
* no struct page in dom0's mem_map for the foreign frame. An HVM
* mapping records the node Xen reported for the frame when it was
* mapped. Its placeholder pages' own node is no substitute: when
* Xen did not say (a driver domain, a hypervisor without the query,
* a kernel without CONFIG_XEN_BACKEND_NUMA_AFFINITY), they come from
* the pool of whichever CPU xenwatch happened to run on, and every
* ring would report that one node.
*/
if (xen_pv_domain())
return NUMA_NO_NODE;

page = vmalloc_to_page(vaddr);
if (!page)
return NUMA_NO_NODE;
spin_lock(&xenbus_valloc_lock);
list_for_each_entry(node, &xenbus_valloc_pages, next) {
if (node->hvm.addr == vaddr) {
host_node = node->hvm.host_node;
break;
}
}
spin_unlock(&xenbus_valloc_lock);

return page_to_nid(page);
return host_node;
}
EXPORT_SYMBOL_GPL(xenbus_ring_host_node);

Expand Down
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