As part of hunting down a race-condition with SWIOTLB, I resurrected this
patch from Virtual Iron's patchset to help me along. It didn't help that much
(still working on the bug), but this might be useful for other situations
Here it is:
 Provided a routine to print the active grant table entries.
 This can be called by command 'g' from the xen console.
 Also, provided a command (invoked by 'G' from the xen console)
 to forcibly increment the pin count of some arbitrary
 grant table entry. This can be used to test the
 printing feature.
Authored-By: Robert Phillips
Signed-off-By: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
diff -r 8b0f1f37e145 xen/common/grant_table.c
--- a/xen/common/grant_table.c Sun Aug 16 08:46:08 2009 +0100
+++ b/xen/common/grant_table.c Mon Sep 14 11:33:32 2009 -0400
@@ -1857,6 +1857,119 @@
 d->grant_table = NULL;
 }
 
+#define GNTTAB_USAGE_PROFILE
+#ifdef GNTTAB_USAGE_PROFILE
+
+#include <xen/keyhandler.h>
+
+void gnttab_usage_print(struct domain *rd)
+{
+ int first = 1;
+ grant_ref_t ref;
+ printk(" -------- active -------- -------- shared --------\n");
+ printk("[ref] localdom mfn pin localdom gmfn flags\n");
+
+ spin_lock(&rd->grant_table->lock);
+ for (ref = 0; ref != nr_grant_entries(rd->grant_table); ref++) {
+ struct active_grant_entry *act;
+ struct grant_entry *sha;
+ act = &active_entry(rd->grant_table, ref);
+ sha = &shared_entry(rd->grant_table, ref);
+ if (act->pin) {
+ if (first) {
+ printk("grant-table for remote domain:%5d\n", rd->domain_id);
+ first = 0;
+ }
+ // [ddd] ddddd 0xXXXXXX 0xXXXXXXXX ddddd 0xXXXXXX 0xXX
+ printk("[%3d] %5d 0x%06lx 0x%08x %5d 0x%06x 0x%02x\n",
+ ref, act->domid, act->frame, act->pin, sha->domid, 
sha->frame, sha->flags);
+ }
+ }
+ spin_unlock(&rd->grant_table->lock);
+ if (first)
+ printk("grant-table for remote domain:%5d ... no active grant table 
entries\n", rd->domain_id);
+}
+
+static void gnttab_usage_print_all(unsigned char key)
+{
+ struct domain *d;
+ printk("%s [ key '%c' pressed\n", __FUNCTION__, key);
+ for_each_domain(d) {
+ gnttab_usage_print(d);
+ }
+ printk("%s ] done\n", __FUNCTION__);
+}
+
+static int gnttab_incr_pin_one(struct domain *rd)
+{
+ int first = 1;
+ grant_ref_t ref;
+ printk(" -------- active -------- -------- shared --------\n");
+ printk("[ref] localdom mfn pin localdom gmfn flags\n");
+
+ spin_lock(&rd->grant_table->lock);
+ for (ref = 0; ref != nr_grant_entries(rd->grant_table); ref++) {
+ struct active_grant_entry *act;
+ struct grant_entry *sha;
+ act = &active_entry(rd->grant_table, ref);
+ sha = &shared_entry(rd->grant_table, ref);
+ if (act->pin) {
+ printk("grant-table for remote domain:%5d\n", rd->domain_id);
+ first = 0;
+ // [ddd] ddddd 0xXXXXXX 0xXXXXXXXX ddddd 0xXXXXXX 0xXX
+ printk("[%3d] %5d 0x%06lx 0x%08x %5d 0x%06x 0x%02x <== 
BEFORE\n",
+ ref, act->domid, act->frame, act->pin, sha->domid, 
sha->frame, sha->flags);
+ act->pin++;
+ get_page(mfn_to_page(act->frame), rd);
+ printk("[%3d] %5d 0x%06lx 0x%08x %5d 0x%06x 0x%02x <== 
AFTER\n",
+ ref, act->domid, act->frame, act->pin, sha->domid, 
sha->frame, sha->flags);
+ break;
+ }
+ }
+ spin_unlock(&rd->grant_table->lock);
+ if (first) {
+ printk("grant-table for remote domain:%5d ... no active grant table 
entries\n", rd->domain_id);
+ return 0;
+ }
+ return 1;
+}
+
+static void gnttab_incr_pin(unsigned char key)
+{
+ struct domain *d;
+ printk("%s [ key '%c' pressed\n", __FUNCTION__, key);
+ for_each_domain(d) {
+ if (gnttab_incr_pin_one(d))
+ break;
+ }
+ printk("%s ] done\n", __FUNCTION__);
+}
+static struct keyhandler gnttab_usage_print_all_keyhandler = {
+ .diagnostic = 1,
+ .u.fn = gnttab_usage_print_all,
+ .desc = "print grant table usage"
+};
+
+
+static struct keyhandler gnttab_incr_pin_keyhandler = {
+ .diagnostic = 1,
+ .u.fn = gnttab_incr_pin,
+ .desc = "force +1 in grant table pin entry"
+};
+
+
+static int __init gnttab_usage_init(void)
+{
+ register_keyhandler('g', &gnttab_usage_print_all_keyhandler);
+ register_keyhandler('G', &gnttab_incr_pin_keyhandler);
+ return 0;
+}
+
+__initcall(gnttab_usage_init);
+
+#endif
+
+
 /*
 * Local variables:
 * mode: C
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