On Mon, 2011-08-01 at 13:38 +0100, Olaf Hering wrote:
> # HG changeset patch
> # User Olaf Hering <olaf@xxxxxxxxx>
> # Date 1312202176 -7200
> # Node ID edb96c34f4a638e8ba97933b6bd76ff72836353e
> # Parent 0f36c2eec2e1576b4db6538b5f22d625587c1a15
> xenstored: allow guests to reintroduce themselves
>
> During kexec all old watches have to be removed, otherwise the new
> kernel will receive unexpected events. Allow a guest to introduce itself
> and cleanup all of its watches.
Just out of interest what happens if a guest tries to use this operation
on an older xenstored which does not support it? I guess it gets an
enosys type response?
Is there any way we can arrange to probe for this feature in order to
fail to register for kexec/kdump early on rather than failing at the
point where we attempt to actually kexec (where failure might come as
rather an unpleasant surprise). I don't think we've historically had a
mechanism for negotiating features with xenstored itself so I'm not sure
what would be best here. Perhaps xenstored itself should
expose /xenstored/feature-FOO nodes?
Ian.
>
> Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>
>
> diff -r 0f36c2eec2e1 -r edb96c34f4a6 tools/xenstore/xenstored_domain.c
> --- a/tools/xenstore/xenstored_domain.c
> +++ b/tools/xenstore/xenstored_domain.c
> @@ -315,7 +315,7 @@ void do_introduce(struct connection *con
> {
> struct domain *domain;
> char *vec[3];
> - unsigned int domid;
> + unsigned int domid, target;
> unsigned long mfn;
> evtchn_port_t port;
> int rc;
> @@ -326,7 +326,7 @@ void do_introduce(struct connection *con
> return;
> }
>
> - if (conn->id != 0 || !conn->can_write) {
> + if (!conn->can_write) {
> send_error(conn, EACCES);
> return;
> }
> @@ -340,19 +340,26 @@ void do_introduce(struct connection *con
> send_error(conn, EINVAL);
> return;
> }
> + /* Allow guest to reset all watches */
> + if (domid != DOMID_SELF && conn->id != 0) {
> + send_error(conn, EACCES);
> + return;
> + }
>
> - domain = find_domain_by_domid(domid);
> + target = domid == DOMID_SELF ? conn->id : domid;
> +
> + domain = find_domain_by_domid(target);
>
> if (domain == NULL) {
> interface = xc_map_foreign_range(
> - *xc_handle, domid,
> + *xc_handle, target,
> getpagesize(), PROT_READ|PROT_WRITE, mfn);
> if (!interface) {
> send_error(conn, errno);
> return;
> }
> /* Hang domain off "in" until we're finished. */
> - domain = new_domain(in, domid, port);
> + domain = new_domain(in, target, port);
> if (!domain) {
> munmap(interface, getpagesize());
> send_error(conn, errno);
> @@ -365,11 +372,11 @@ void do_introduce(struct connection *con
> talloc_steal(domain->conn, domain);
>
> fire_watches(NULL, "@introduceDomain", false);
> - } else if ((domain->mfn == mfn) && (domain->conn != conn)) {
> + } else if ((domain->mfn == mfn) && ((domain->conn != conn) || domid ==
> DOMID_SELF)) {
> /* Use XS_INTRODUCE for recreating the xenbus event-channel. */
> if (domain->port)
> xc_evtchn_unbind(xce_handle, domain->port);
> - rc = xc_evtchn_bind_interdomain(xce_handle, domid, port);
> + rc = xc_evtchn_bind_interdomain(xce_handle, target, port);
> domain->port = (rc == -1) ? 0 : rc;
> domain->remote_port = port;
> } else {
>
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