On 28.04.20 22:55, Julien Grall wrote:
Hi Juergen,
On Tue, 28 Apr 2020 at 16:53, Juergen Gross <jgr...@suse.com> wrote:
The XS_INTRODUCE command has two parameters: the mfn (or better: gfn)
of the domain's xenstore ring page and the event channel of the
domain for communicating with Xenstore.
The gfn is not really needed. It is stored in the per-domain struct
in xenstored and in case of another XS_INTRODUCE for the domain it
is tested to match the original value. If it doesn't match the
command is aborted via EINVAL.
Today there shouldn't be multiple XS_INTRODUCE requests for the same
domain issued, so the mfn/gfn can just be ignored and multiple
XS_INTRODUCE commands can be rejected without testing the mfn/gfn.
So there is a comment in the else part:
/* Use XS_INTRODUCE for recreating the xenbus event-channel. */
From the commit message this is not entirely clear why we want to
prevent recreating the event-channel. Can you expand it?
Recreating the event channel would be fine, but I don't see why it
would ever be needed. And XS_INTRODUCE is called only at domain creation
time today, so there is obviously no need for repeating this call.
Maybe the idea was to do this after sending a XS_RESUME command, which
isn't used anywhere in Xen and is another part of Xenstore which doesn't
make any sense today.
Signed-off-by: Juergen Gross <jgr...@suse.com>
---
tools/xenstore/xenstored_domain.c | 47 ++++++++++++++++-----------------------
1 file changed, 19 insertions(+), 28 deletions(-)
diff --git a/tools/xenstore/xenstored_domain.c
b/tools/xenstore/xenstored_domain.c
index 5858185211..17328f9fc9 100644
--- a/tools/xenstore/xenstored_domain.c
+++ b/tools/xenstore/xenstored_domain.c
@@ -369,7 +369,6 @@ int do_introduce(struct connection *conn, struct
buffered_data *in)
struct domain *domain;
char *vec[3];
unsigned int domid;
- unsigned long mfn;
evtchn_port_t port;
int rc;
struct xenstore_domain_interface *interface;
@@ -381,7 +380,7 @@ int do_introduce(struct connection *conn, struct
buffered_data *in)
return EACCES;
domid = atoi(vec[0]);
- mfn = atol(vec[1]);
+ /* Ignore the mfn, we don't need it. */
s/mfn/GFN/
Okay, then I should probably change the parameter description, too.
port = atoi(vec[2]);
/* Sanity check args. */
@@ -390,34 +389,26 @@ int do_introduce(struct connection *conn, struct
buffered_data *in)
domain = find_domain_by_domid(domid);
- if (domain == NULL) {
- interface = map_interface(domid);
- if (!interface)
- return errno;
- /* Hang domain off "in" until we're finished. */
- domain = new_domain(in, domid, port);
- if (!domain) {
- rc = errno;
- unmap_interface(interface);
- return rc;
- }
- domain->interface = interface;
- domain->mfn = mfn;
AFAICT domain->mfn is not used anymore, so could we remove the field?
Oh, yes, I missed that.
Juergen
