Re: [PATCH v5 03/10] hw/tpm: Add internal buffer state for chunking

[Stefan Berger]

On 4/22/26 6:30 AM, Arun Menon wrote:

From: Arun Menon <arme...@redhat.com>

- Introduce GByteArray buffers to hold the command request and response
   data during chunked TPM CRB transactions.
- Add helper function to clean them.

Signed-off-by: Arun Menon <arme...@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lur...@redhat.com>

Reviewed-by: Stefan Berger <stef...@linux.ibm.com>

---
  hw/tpm/tpm_crb.c | 33 +++++++++++++++++++++++++++++----
  1 file changed, 29 insertions(+), 4 deletions(-)

diff --git a/hw/tpm/tpm_crb.c b/hw/tpm/tpm_crb.c
index 7edfbf8f8a..e7ec9d0679 100644
--- a/hw/tpm/tpm_crb.c
+++ b/hw/tpm/tpm_crb.c
@@ -38,10 +38,13 @@ struct CRBState {
      TPMBackend *tpmbe;
      TPMBackendCmd cmd;
      uint32_t regs[TPM_CRB_R_MAX];
+    size_t be_buffer_size;
      MemoryRegion mmio;
      MemoryRegion cmdmem;

-    size_t be_buffer_size;
+    GByteArray *command_buffer;
+    GByteArray *response_buffer;
+    uint32_t response_offset;

      bool ppi_enabled;
      TPMPPI ppi;
@@ -87,6 +90,13 @@ enum crb_cancel {

  #define TPM_CRB_NO_LOCALITY 0xff

+static void tpm_crb_clear_internal_buffers(CRBState *s)
+{
+    g_byte_array_set_size(s->response_buffer, 0);
+    g_byte_array_set_size(s->command_buffer, 0);
+    s->response_offset = 0;
+}
+
  static uint64_t tpm_crb_mmio_read(void *opaque, hwaddr addr,
                                    unsigned size)
  {
@@ -136,9 +146,11 @@ static void tpm_crb_mmio_write(void *opaque, hwaddr addr,
          }
          break;
      case A_CRB_CTRL_CANCEL:
-        if (val == CRB_CANCEL_INVOKE &&
-            s->regs[R_CRB_CTRL_START] & CRB_START_INVOKE) {
-            tpm_backend_cancel_cmd(s->tpmbe);
+        if (val == CRB_CANCEL_INVOKE) {
+            if (s->regs[R_CRB_CTRL_START] & CRB_START_INVOKE) {
+                tpm_backend_cancel_cmd(s->tpmbe);
+            }
+            tpm_crb_clear_internal_buffers(s);
          }
          break;
      case A_CRB_CTRL_START:
@@ -243,6 +255,7 @@ static void tpm_crb_reset(void *dev)
          tpm_ppi_reset(&s->ppi);
      }
      tpm_backend_reset(s->tpmbe);
+    tpm_crb_clear_internal_buffers(s);

      memset(s->regs, 0, sizeof(s->regs));

@@ -309,6 +322,9 @@ static void tpm_crb_realize(DeviceState *dev, Error **errp)
      memory_region_add_subregion(get_system_memory(),
          TPM_CRB_ADDR_BASE + sizeof(s->regs), &s->cmdmem);

+    s->command_buffer = g_byte_array_new();
+    s->response_buffer = g_byte_array_new();
+
      if (s->ppi_enabled) {
          tpm_ppi_init(&s->ppi, get_system_memory(),
                       TPM_PPI_ADDR_BASE, OBJECT(s));
@@ -321,12 +337,21 @@ static void tpm_crb_realize(DeviceState *dev, Error 
**errp)
      }
  }

+static void tpm_crb_unrealize(DeviceState *dev)
+{
+    CRBState *s = CRB(dev);
+
+    g_clear_pointer(&s->command_buffer, g_byte_array_unref);
+    g_clear_pointer(&s->response_buffer, g_byte_array_unref);
+}
+
  static void tpm_crb_class_init(ObjectClass *klass, const void *data)
  {
      DeviceClass *dc = DEVICE_CLASS(klass);
      TPMIfClass *tc = TPM_IF_CLASS(klass);

      dc->realize = tpm_crb_realize;
+    dc->unrealize = tpm_crb_unrealize;
      device_class_set_props(dc, tpm_crb_properties);
      dc->vmsd  = &vmstate_tpm_crb;
      dc->user_creatable = true;