[Qemu-devel] [PATCH v4 1/2] spapr: Add a "no HPT" encoding to HTAB migration stream

[Bharata B Rao]

Add a "no HPT" encoding (using value -1) to the HTAB migration
stream (in the place of HPT size) when the guest doesn't allocate HPT.
This will help the target side to match target HPT with the source HPT
and thus enable successful migration.

A few more fixes to enable TCG migration to work correctly are also
included in this commit:

- HTAB savevm handlers have a few asserts on kvm_enabled() when
  spapr->htab != 0. Convert these into conditional checks as it is now
  possible to have no HTAB with TCG radix guests.
- htab_save_setup() asserts for kvm_enabled() when spapr->htab != 0.
  Remove this as we can't assert this for TCG radix guests.

Suggested-by: David Gibson <da...@gibson.dropbear.id.au>
              [no HPT encoding suggestion]
Signed-off-by: Bharata B Rao <bhar...@linux.vnet.ibm.com>
---
 hw/ppc/spapr.c | 31 +++++++++++++++++--------------
 1 file changed, 17 insertions(+), 14 deletions(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index ab3aab1..b589ed4 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1559,17 +1559,18 @@ static int htab_save_setup(QEMUFile *f, void *opaque)
 {
     sPAPRMachineState *spapr = opaque;
 
-    /* "Iteration" header */
-    qemu_put_be32(f, spapr->htab_shift);
+    /* "Iteration" header: no-HPT or HPT size encoding */
+    if (!spapr->htab_shift) {
+        qemu_put_be32(f, -1);
+    } else {
+        qemu_put_be32(f, spapr->htab_shift);
+    }
 
     if (spapr->htab) {
         spapr->htab_save_index = 0;
         spapr->htab_first_pass = true;
-    } else {
-        assert(kvm_enabled());
     }
 
-
     return 0;
 }
 
@@ -1714,9 +1715,7 @@ static int htab_save_iterate(QEMUFile *f, void *opaque)
     /* Iteration header */
     qemu_put_be32(f, 0);
 
-    if (!spapr->htab) {
-        assert(kvm_enabled());
-
+    if (!spapr->htab && kvm_enabled()) {
         fd = get_htab_fd(spapr);
         if (fd < 0) {
             return fd;
@@ -1748,7 +1747,7 @@ static int htab_save_complete(QEMUFile *f, void *opaque)
     /* Iteration header */
     qemu_put_be32(f, 0);
 
-    if (!spapr->htab) {
+    if (!spapr->htab && kvm_enabled()) {
         int rc;
 
         assert(kvm_enabled());
@@ -1793,6 +1792,12 @@ static int htab_load(QEMUFile *f, void *opaque, int 
version_id)
     if (section_hdr) {
         Error *local_err = NULL;
 
+        if (section_hdr == -1) {
+            spapr_free_hpt(spapr);
+            unregister_savevm(NULL, "spapr/htab", spapr);
+            return 0;
+        }
+
         /* First section gives the htab size */
         spapr_reallocate_hpt(spapr, section_hdr, &local_err);
         if (local_err) {
@@ -1802,9 +1807,7 @@ static int htab_load(QEMUFile *f, void *opaque, int 
version_id)
         return 0;
     }
 
-    if (!spapr->htab) {
-        assert(kvm_enabled());
-
+    if (!spapr->htab && kvm_enabled()) {
         fd = kvmppc_get_htab_fd(true);
         if (fd < 0) {
             error_report("Unable to open fd to restore KVM hash table: %s",
@@ -1843,7 +1846,7 @@ static int htab_load(QEMUFile *f, void *opaque, int 
version_id)
                 memset(HPTE(spapr->htab, index + n_valid), 0,
                        HASH_PTE_SIZE_64 * n_invalid);
             }
-        } else {
+        } else if (kvm_enabled()) {
             int rc;
 
             assert(fd >= 0);
@@ -1855,7 +1858,7 @@ static int htab_load(QEMUFile *f, void *opaque, int 
version_id)
         }
     }
 
-    if (!spapr->htab) {
+    if (!spapr->htab && kvm_enabled()) {
         assert(fd >= 0);
         close(fd);
     }
-- 
2.7.4