From: Arun Menon <armenon@redhat.com>

- Add subsection in VMState for TPM CRB with the newly introduced
  command and response buffers, along with a needed callback, so that
  newer QEMU only sends the buffers if it is necessary.
- Add hw_compat blocker because the feature is only supported for
  machine type 11.1 and higher.
- If the VM has no pending chunked TPM commands in the internal buffers
  during a VM migration, or if the machine type does not support newly
  introduced buffers, then the needed callback will return false, as it
  checks the hw_compat blocker and thus the subsection will not be sent
  to the destination host.

Signed-off-by: Arun Menon <armenon@redhat.com>
---
 hw/core/machine.c |  4 +++-
 hw/tpm/tpm_crb.c  | 31 +++++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/hw/core/machine.c b/hw/core/machine.c
index 1abc8ae737..fb290c6c53 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -38,7 +38,9 @@
 #include "hw/acpi/generic_event_device.h"
 #include "qemu/audio.h"
 
-GlobalProperty hw_compat_11_0[] = {};
+GlobalProperty hw_compat_11_0[] = {
+    { "tpm-crb", "migrate-buffers", "off"},
+};
 const size_t hw_compat_11_0_len = G_N_ELEMENTS(hw_compat_11_0);
 
 GlobalProperty hw_compat_10_2[] = {
diff --git a/hw/tpm/tpm_crb.c b/hw/tpm/tpm_crb.c
index b9f295db7a..81471dd9f8 100644
--- a/hw/tpm/tpm_crb.c
+++ b/hw/tpm/tpm_crb.c
@@ -49,6 +49,8 @@ struct CRBState {
 
     bool ppi_enabled;
     TPMPPI ppi;
+
+    bool migrate_buffers;
 };
 typedef struct CRBState CRBState;
 
@@ -345,18 +347,47 @@ static int tpm_crb_pre_save(void *opaque)
     return 0;
 }
 
+static bool tpm_crb_chunk_needed(void *opaque)
+{
+    CRBState *s = opaque;
+
+    if (!s->migrate_buffers) {
+        return false;
+    }
+
+    return ((s->command_buffer && s->command_buffer->len > 0) ||
+            (s->response_buffer && s->response_buffer->len > 0));
+}
+
+static const VMStateDescription vmstate_tpm_crb_chunk = {
+    .name = "tpm-crb/chunk",
+    .version_id = 0,
+    .needed = tpm_crb_chunk_needed,
+    .fields = (const VMStateField[]) {
+        VMSTATE_GBYTEARRAY(command_buffer, CRBState, 0),
+        VMSTATE_GBYTEARRAY(response_buffer, CRBState, 0),
+        VMSTATE_UINT32(response_offset, CRBState),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 static const VMStateDescription vmstate_tpm_crb = {
     .name = "tpm-crb",
     .pre_save = tpm_crb_pre_save,
     .fields = (const VMStateField[]) {
         VMSTATE_UINT32_ARRAY(regs, CRBState, TPM_CRB_R_MAX),
         VMSTATE_END_OF_LIST(),
+    },
+    .subsections = (const VMStateDescription * const []) {
+        &vmstate_tpm_crb_chunk,
+        NULL,
     }
 };
 
 static const Property tpm_crb_properties[] = {
     DEFINE_PROP_TPMBE("tpmdev", CRBState, tpmbe),
     DEFINE_PROP_BOOL("ppi", CRBState, ppi_enabled, true),
+    DEFINE_PROP_BOOL("migrate-buffers", CRBState, migrate_buffers, true),
 };
 
 static void tpm_crb_reset(void *dev)
-- 
2.53.0