[xen stable-4.15] docs/design: Update xenstore-migration.md

[patchbot@xxxxxxx]

commit 7ff29c96dee274826bc375b77dee8db0ce930344
Author:     Julien Grall <jgrall@xxxxxxxxxx>
AuthorDate: Thu Mar 25 10:42:46 2021 +0000
Commit:     Julien Grall <jgrall@xxxxxxxxxx>
CommitDate: Fri Mar 26 12:13:16 2021 +0000

    docs/design: Update xenstore-migration.md
    
    It is not very clear the shared page adddress is not contained in the
    connection record. Additionally, it is misleading to say the grant
    will always point to the share paged as a domain is free to revoke the
    permission. The restore code would need to make sure it doesn't
    fail/crash if this is happening.
    
    The sentence is now replaced with a paragraph explaining why the GFN is
    not preserved and that the grant is not guarantee to exist during
    restore.
    
    Take the opportunity to replace "code" with "node" when description the
    permission.
    
    Reported-by: Raphael Ning <raphning@xxxxxxxxxx>
    Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
    Reviewed-by: Juergen Gross <jgross@xxxxxxxx>
    Release-Acked-by: Ian Jackson <iwj@xxxxxxxxxxxxxx>
    (cherry picked from commit 7b6d288ef648c76da70fd9e41e73617631025cfe)
---
 docs/designs/xenstore-migration.md | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/docs/designs/xenstore-migration.md 
b/docs/designs/xenstore-migration.md
index 1a5b94b31d..5f1155273e 100644
--- a/docs/designs/xenstore-migration.md
+++ b/docs/designs/xenstore-migration.md
@@ -216,8 +216,10 @@ For `shared ring` connections it is as follows:
 |           | by xenstored to communicate with `domid`          |
 |           |                                                   |
 
-Since the ABI guarantees that entry 1 in `domid`'s grant table will always
-contain the GFN of the shared page.
+The GFN of the shared page is not preserved because the ABI reserves
+entry 1 in `domid`'s grant table to point to the xenstore shared page.
+Note there is no guarantee the page will still be valid at the time of
+the restore because a domain can revoke the permission.
 
 For `socket` connections it is as follows:
 
@@ -398,7 +400,7 @@ A node permission specifier has the following format:
 |         |                                                     |
 | `domid` | The domain-id to which the permission relates       |
 
-Note that perm1 defines the domain owning the code. See [4] for more
+Note that perm1 defines the domain owning the node. See [4] for more
 explanation of node permissions.
 
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