This should be backported to the 4.1 branch; it causes a hypervisor
BUG() if guests are using netchannel2 transtiive grants to talk to
each other when debug mode is on.
-George
On Tue, Mar 8, 2011 at 3:02 PM, George Dunlap
<george.dunlap@xxxxxxxxxxxxx> wrote:
> When acquiring a transitive grant for copy then the owning domain needs to
> be locked down as well as the granting domain. This was being done, but the
> unlocking was not. The acquire code now stores the struct domain * of the
> owning domain (rather than the domid) in the active entry in the granting
> domain. The release code then does the unlock on the owning domain.
> Note that I believe I also fixed a bug where, for non-transitive grants
> the active entry contained a reference to the acquiring domain rather
> than the granting domain. From my reading of the code this would stop the
> release code for transitive grants from terminating its recursion
> correctly.
>
> Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
> CC: Steven Smith <steven.smith@xxxxxxxxxx>
>
> diff -r f071d8e9f744 -r 14211e98efac xen/common/grant_table.c
> --- a/xen/common/grant_table.c Tue Mar 08 10:23:52 2011 +0000
> +++ b/xen/common/grant_table.c Tue Mar 08 14:39:03 2011 +0000
> @@ -1626,11 +1626,10 @@
> struct active_grant_entry *act;
> unsigned long r_frame;
> uint16_t *status;
> - domid_t trans_domid;
> grant_ref_t trans_gref;
> int released_read;
> int released_write;
> - struct domain *trans_dom;
> + struct domain *td;
>
> released_read = 0;
> released_write = 0;
> @@ -1644,15 +1643,13 @@
> if (rd->grant_table->gt_version == 1)
> {
> status = &sha->flags;
> - trans_domid = rd->domain_id;
> - /* Shut the compiler up. This'll never be used, because
> - trans_domid == rd->domain_id, but gcc doesn't know that. */
> - trans_gref = 0x1234567;
> + td = rd;
> + trans_gref = gref;
> }
> else
> {
> status = &status_entry(rd->grant_table, gref);
> - trans_domid = act->trans_dom;
> + td = act->trans_domain;
> trans_gref = act->trans_gref;
> }
>
> @@ -1680,21 +1677,16 @@
>
> spin_unlock(&rd->grant_table->lock);
>
> - if ( trans_domid != rd->domain_id )
> + if ( td != rd )
> {
> - if ( released_write || released_read )
> - {
> - trans_dom = rcu_lock_domain_by_id(trans_domid);
> - if ( trans_dom != NULL )
> - {
> - /* Recursive calls, but they're tail calls, so it's
> - okay. */
> - if ( released_write )
> - __release_grant_for_copy(trans_dom, trans_gref, 0);
> - else if ( released_read )
> - __release_grant_for_copy(trans_dom, trans_gref, 1);
> - }
> - }
> + /* Recursive calls, but they're tail calls, so it's
> + okay. */
> + if ( released_write )
> + __release_grant_for_copy(td, trans_gref, 0);
> + else if ( released_read )
> + __release_grant_for_copy(td, trans_gref, 1);
> +
> + rcu_unlock_domain(td);
> }
> }
>
> @@ -1731,7 +1723,7 @@
> uint32_t old_pin;
> domid_t trans_domid;
> grant_ref_t trans_gref;
> - struct domain *rrd;
> + struct domain *td;
> unsigned long gfn;
> unsigned long grant_frame;
> unsigned trans_page_off;
> @@ -1785,8 +1777,8 @@
> status) ) != GNTST_okay )
> goto unlock_out;
>
> - trans_domid = ld->domain_id;
> - trans_gref = 0;
> + td = rd;
> + trans_gref = gref;
> if ( sha2 && (shah->flags & GTF_type_mask) == GTF_transitive )
> {
> if ( !allow_transitive )
> @@ -1808,14 +1800,15 @@
> that you don't need to go out of your way to avoid it
> in the guest. */
>
> - rrd = rcu_lock_domain_by_id(trans_domid);
> - if ( rrd == NULL )
> + /* We need to leave the rrd locked during the grant copy */
> + td = rcu_lock_domain_by_id(trans_domid);
> + if ( td == NULL )
> PIN_FAIL(unlock_out, GNTST_general_error,
> "transitive grant referenced bad domain %d\n",
> trans_domid);
> spin_unlock(&rd->grant_table->lock);
>
> - rc = __acquire_grant_for_copy(rrd, trans_gref, rd,
> + rc = __acquire_grant_for_copy(td, trans_gref, rd,
> readonly, &grant_frame,
> &trans_page_off, &trans_length,
> 0, &ignore);
> @@ -1823,6 +1816,7 @@
> spin_lock(&rd->grant_table->lock);
> if ( rc != GNTST_okay ) {
> __fixup_status_for_pin(act, status);
> + rcu_unlock_domain(td);
> spin_unlock(&rd->grant_table->lock);
> return rc;
> }
> @@ -1834,6 +1828,7 @@
> if ( act->pin != old_pin )
> {
> __fixup_status_for_pin(act, status);
> + rcu_unlock_domain(td);
> spin_unlock(&rd->grant_table->lock);
> return __acquire_grant_for_copy(rd, gref, ld, readonly,
> frame, page_off, length,
> @@ -1845,7 +1840,7 @@
> sub-page, but we always treat it as one because that
> blocks mappings of transitive grants. */
> is_sub_page = 1;
> - *owning_domain = rrd;
> + *owning_domain = td;
> act->gfn = -1ul;
> }
> else if ( sha1 )
> @@ -1891,7 +1886,7 @@
> act->is_sub_page = is_sub_page;
> act->start = trans_page_off;
> act->length = trans_length;
> - act->trans_dom = trans_domid;
> + act->trans_domain = td;
> act->trans_gref = trans_gref;
> act->frame = grant_frame;
> }
> diff -r f071d8e9f744 -r 14211e98efac xen/include/xen/grant_table.h
> --- a/xen/include/xen/grant_table.h Tue Mar 08 10:23:52 2011 +0000
> +++ b/xen/include/xen/grant_table.h Tue Mar 08 14:39:03 2011 +0000
> @@ -32,7 +32,7 @@
> struct active_grant_entry {
> u32 pin; /* Reference count information. */
> domid_t domid; /* Domain being granted access. */
> - domid_t trans_dom;
> + struct domain *trans_domain;
> uint32_t trans_gref;
> unsigned long frame; /* Frame being granted. */
> unsigned long gfn; /* Guest's idea of the frame being granted. */
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-devel
>
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