vfio: Add capability chain helpers

Allow sub-modules to easily reallocate a buffer for managing
capability chains for info ioctls.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 4cc961b..6fd6fa5 100644 (file)
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -1729,6 +1729,60 @@ long vfio_external_check_extension(struct vfio_group *group, unsigned long arg)
 EXPORT_SYMBOL_GPL(vfio_external_check_extension);
 
 /**
+ * Sub-module support
+ */
+/*
+ * Helper for managing a buffer of info chain capabilities, allocate or
+ * reallocate a buffer with additional @size, filling in @id and @version
+ * of the capability.  A pointer to the new capability is returned.
+ *
+ * NB. The chain is based at the head of the buffer, so new entries are
+ * added to the tail, vfio_info_cap_shift() should be called to fixup the
+ * next offsets prior to copying to the user buffer.
+ */
+struct vfio_info_cap_header *vfio_info_cap_add(struct vfio_info_cap *caps,
+                                              size_t size, u16 id, u16 version)
+{
+       void *buf;
+       struct vfio_info_cap_header *header, *tmp;
+
+       buf = krealloc(caps->buf, caps->size + size, GFP_KERNEL);
+       if (!buf) {
+               kfree(caps->buf);
+               caps->size = 0;
+               return ERR_PTR(-ENOMEM);
+       }
+
+       caps->buf = buf;
+       header = buf + caps->size;
+
+       /* Eventually copied to user buffer, zero */
+       memset(header, 0, size);
+
+       header->id = id;
+       header->version = version;
+
+       /* Add to the end of the capability chain */
+       for (tmp = caps->buf; tmp->next; tmp = (void *)tmp + tmp->next)
+               ; /* nothing */
+
+       tmp->next = caps->size;
+       caps->size += size;
+
+       return header;
+}
+EXPORT_SYMBOL_GPL(vfio_info_cap_add);
+
+void vfio_info_cap_shift(struct vfio_info_cap *caps, size_t offset)
+{
+       struct vfio_info_cap_header *tmp;
+
+       for (tmp = caps->buf; tmp->next; tmp = (void *)tmp + tmp->next - offset)
+               tmp->next += offset;
+}
+EXPORT_SYMBOL_GPL(vfio_info_cap_shift);
+
+/**
  * Module/class support
  */
 static char *vfio_devnode(struct device *dev, umode_t *mode)

diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index 610a86a..0ecae0b 100644 (file)
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -92,6 +92,17 @@ extern int vfio_external_user_iommu_id(struct vfio_group *group);
 extern long vfio_external_check_extension(struct vfio_group *group,
                                          unsigned long arg);
 
+/*
+ * Sub-module helpers
+ */
+struct vfio_info_cap {
+       struct vfio_info_cap_header *buf;
+       size_t size;
+};
+extern struct vfio_info_cap_header *vfio_info_cap_add(
+               struct vfio_info_cap *caps, size_t size, u16 id, u16 version);
+extern void vfio_info_cap_shift(struct vfio_info_cap *caps, size_t offset);
+
 struct pci_dev;
 #ifdef CONFIG_EEH
 extern void vfio_spapr_pci_eeh_open(struct pci_dev *pdev);