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Subject[PATCH 1/6] xen: add functions for mapping foreign pages over pages
Date
From: David Vrabel <david.vrabel@citrix.com>

Add xenbus_map_ring_page() and xenbus_unmap_ring_page() which map and
unmap foreign pages over a page instead of mapping them into vmalloc
address space. This avoids having to do an expensive
vmalloc_sync_all().

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
---
drivers/xen/xenbus/xenbus_client.c | 68 ++++++++++++++++++++++++++++++++++++
include/xen/xenbus.h | 3 ++
2 files changed, 71 insertions(+), 0 deletions(-)
diff --git a/drivers/xen/xenbus/xenbus_client.c b/drivers/xen/xenbus/xenbus_client.c
index cdacf92..504325b 100644
--- a/drivers/xen/xenbus/xenbus_client.c
+++ b/drivers/xen/xenbus/xenbus_client.c
@@ -32,6 +32,7 @@

#include <linux/slab.h>
#include <linux/types.h>
+#include <linux/mm.h>
#include <linux/vmalloc.h>
#include <asm/xen/hypervisor.h>
#include <xen/interface/xen.h>
@@ -39,6 +40,7 @@
#include <xen/events.h>
#include <xen/grant_table.h>
#include <xen/xenbus.h>
+#include <xen/page.h>

const char *xenbus_strstate(enum xenbus_state state)
{
@@ -509,6 +511,44 @@ EXPORT_SYMBOL_GPL(xenbus_map_ring);


/**
+ * xenbus_map_ring_page - map a foreign page into a kernel page
+ * @dev: xenbus device
+ * @gnt_ref: grant reference
+ * @page: return the page the foreign page has been mapped to
+ *
+ * Map a foreign page from another domain's grant table into a newly
+ * allocated page in this domain. The page must be unmapped with
+ * xenbus_unmap_ring_page().
+ *
+ * Returns 0 on success, and -ENOMEM or GNTST_* (see
+ * include/xen/interface/grant_table.h) on error.
+ */
+int xenbus_map_ring_page(struct xenbus_device *dev, int gnt_ref,
+ struct page **page)
+{
+ struct page *new_page;
+ grant_ref_t handle;
+ int ret;
+
+ new_page = alloc_page(GFP_KERNEL);
+ if (!new_page)
+ return -ENOMEM;
+
+ ret = xenbus_map_ring(dev, gnt_ref, &handle, page_address(new_page));
+ if (ret < 0)
+ goto err;
+
+ new_page->private = handle;
+ *page = new_page;
+ return 0;
+
+err:
+ __free_page(new_page);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(xenbus_map_ring_page);
+
+/**
* xenbus_unmap_ring_vfree
* @dev: xenbus device
* @vaddr: addr to unmap
@@ -593,6 +633,34 @@ int xenbus_unmap_ring(struct xenbus_device *dev,
}
EXPORT_SYMBOL_GPL(xenbus_unmap_ring);

+/**
+ * xenbus_unmap_ring_page - unmap an foreign page from a kernel page
+ * @dev: xenbus device
+ * @page: page the foreign page was mapped to
+ *
+ * Unmap a foreign page previously mapped with xenbus_map_ring_page().
+ * The page is freed.
+ */
+void xenbus_unmap_ring_page(struct xenbus_device *dev, struct page *page)
+{
+ int ret;
+
+ ret = xenbus_unmap_ring(dev, page->private, page_address(page));
+ if (ret < 0)
+ return;
+
+ /*
+ * Restore the original PTE of this page before freeing it.
+ */
+ ret = HYPERVISOR_update_va_mapping(
+ (unsigned long)page_address(page),
+ mfn_pte(get_phys_to_machine(page_to_pfn(page)), PAGE_KERNEL),
+ 0);
+ BUG_ON(ret);
+
+ __free_page(page);
+}
+EXPORT_SYMBOL_GPL(xenbus_unmap_ring_page);

/**
* xenbus_read_driver_state
diff --git a/include/xen/xenbus.h b/include/xen/xenbus.h
index aceeca7..ebde2fd 100644
--- a/include/xen/xenbus.h
+++ b/include/xen/xenbus.h
@@ -212,10 +212,13 @@ int xenbus_map_ring_valloc(struct xenbus_device *dev,
int gnt_ref, void **vaddr);
int xenbus_map_ring(struct xenbus_device *dev, int gnt_ref,
grant_handle_t *handle, void *vaddr);
+int xenbus_map_ring_page(struct xenbus_device *dev, int gnt_ref,
+ struct page **page);

int xenbus_unmap_ring_vfree(struct xenbus_device *dev, void *vaddr);
int xenbus_unmap_ring(struct xenbus_device *dev,
grant_handle_t handle, void *vaddr);
+void xenbus_unmap_ring_page(struct xenbus_device *dev, struct page *page);

int xenbus_alloc_evtchn(struct xenbus_device *dev, int *port);
int xenbus_bind_evtchn(struct xenbus_device *dev, int remote_port, int *port);
--
1.7.2.5


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