On Thu, Oct 29, 2026 at 11:45:41PM +0530, Arun Menon wrote: > From: Arun Menon <[email protected]> > > TPMs implemented with the CRB address map in the TCG PC-Client > Platform TPM Profile (PTP) for TPM 2.0 are limited to a 3968-byte > command/response buffer (v1.07, March 2026, Table 36 and section > 6.5.3.9) in [2]. This is smaller than the 7.7KB ML-DSA-87 TPM2_Load from > the previous patch. PTP 1.07 adds a chunking mode for exactly this case > (sections 6.4.2.2, 6.5.3.9, 6.5.3.10 in [2]), usable by any CRB TPM that > implements it. > > Send and receive the command/response split into pieces no larger than > priv->cmd_size/priv->rsp_size. Write CRB_START_NEXT_CHUNK to > ctrl_start after each piece but the last, and wait for the TPM to clear > it before sending the next; use CRB_START_INVOKE on the last piece, same > as the non-chunked path. Read a response back the same way, in reverse. > > On top of the previous patch's tpm_crb_send_no_chunks()/ > tpm_crb_recv_no_chunks() split, add: > - rsp_size: response-direction counterpart of cmd_size. > - intf_id: interface ID register, read once at probe time. > - CRB_INTF_CAP_CRB_CHUNK: capability bit in intf_id; crb_send()/ > crb_recv() only reject an oversized payload when it is clear. > - tpm_crb_send_chunks()/tpm_crb_recv_chunks(): drive the chunked > transfer described above. > > This corresponds to the backend implementation in QEMU [1], which > reassembles the chunks before handing the command to the TPM emulator. > > [1] > https://lore.kernel.org/qemu-devel/[email protected]/ > [2] > https://medias.cdn.trustedcomputinggroup.org/production/PC_Client_Specific_Platform_TPM_Profile_for_TPM_2p0_v1p07_Pub_5643562943.pdf > > Signed-off-by: Arun Menon <[email protected]> > --- > drivers/char/tpm/tpm_crb.c | 119 +++++++++++++++++++++++++++++++++++-- > 1 file changed, 115 insertions(+), 4 deletions(-) > > diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c > index f0bac9e1f1e8..e14b1feb3fea 100644 > --- a/drivers/char/tpm/tpm_crb.c > +++ b/drivers/char/tpm/tpm_crb.c > @@ -105,11 +105,13 @@ struct crb_priv { > u8 __iomem *cmd; > u8 __iomem *rsp; > u32 cmd_size; > + u32 rsp_size; > u32 smc_func_id; > u32 __iomem *pluton_start_addr; > u32 __iomem *pluton_reply_addr; > u8 ffa_flags; > u8 ffa_attributes; > + u32 intf_id; > }; > > struct tpm2_crb_smc { > @@ -369,6 +371,13 @@ static u8 crb_status(struct tpm_chip *chip) > return sts; > } > > +/* > + * tpm_crb_recv_chunks() below needs to drive CRB_START_NEXT_CHUNK through > + * tpm_crb_start(), which is defined later in this file next to the other > + * platform-specific start methods it dispatches to. > + */ > +static int tpm_crb_start(struct tpm_chip *chip, u32 start_cmd); > + > static int tpm_crb_recv_no_chunks(struct tpm_chip *chip, u8 *buf, size_t > count) > { > struct crb_priv *priv = dev_get_drvdata(&chip->dev); > @@ -388,12 +397,54 @@ static int tpm_crb_recv_no_chunks(struct tpm_chip > *chip, u8 *buf, size_t count) > memcpy_fromio(&buf[8], &priv->rsp[8], expected - 8); > > return expected; > +} > + > +static int tpm_crb_recv_chunks(struct tpm_chip *chip, u8 *buf, size_t count, > + unsigned int expected) > +{ > + struct crb_priv *priv = dev_get_drvdata(&chip->dev); > + size_t offset = 0; > + size_t chunk_size; > + bool expired; > + int rc; > + > + if (expected > count || expected < TPM_HEADER_SIZE) > + return -EIO; > + /* > + * Without this, a bogus zero-sized MMIO window would never make > + * forward progress below. > + */ > + if (priv->rsp_size == 0) > + return -EIO; > + > + while (offset < expected) { > + chunk_size = min_t(size_t, expected - offset, priv->rsp_size); > + memcpy_fromio(buf + offset, priv->rsp, chunk_size); > + offset += chunk_size; > > + if (offset == expected) > + break; > + > + rc = tpm_crb_start(chip, CRB_START_NEXT_CHUNK); > + if (rc) > + return rc; > + > + expired = !crb_wait_for_reg_32(&priv->regs_t->ctrl_start, > + CRB_START_NEXT_CHUNK, 0, > + TPM2_TIMEOUT_C); > + if (expired) { > + dev_err(&chip->dev, > + "Timeout waiting for backend response\n"); > + return -ETIME; > + } > + } > + return expected; > } > > static int crb_recv(struct tpm_chip *chip, u8 *buf, size_t count) > { > struct crb_priv *priv = dev_get_drvdata(&chip->dev); > + unsigned int expected; > > /* > * A sanity check that the upper layer wants to get at least the header > @@ -409,7 +460,17 @@ static int crb_recv(struct tpm_chip *chip, u8 *buf, > size_t count) > if (ioread32(&priv->regs_t->ctrl_sts) & CRB_CTRL_STS_ERROR) > return -EIO; > > - return tpm_crb_recv_no_chunks(chip, buf, count); > + /* Peek at the first 8 bytes to determine the response size */ > + expected = be32_to_cpup((__be32 *)&priv->rsp[2]); > + > + if (expected <= priv->rsp_size) > + return tpm_crb_recv_no_chunks(chip, buf, count); > + if (!(priv->intf_id & CRB_INTF_CAP_CRB_CHUNK)) { > + dev_err(&chip->dev, > + "Response larger than MMIO and chunking not > supported\n"); > + return -EIO; > + } > + return tpm_crb_recv_chunks(chip, buf, count, expected); > } > > static int crb_do_acpi_start(struct tpm_chip *chip) > @@ -502,6 +563,46 @@ static int tpm_crb_send_no_chunks(struct tpm_chip *chip, > u8 *buf, size_t len) > return crb_try_pluton_doorbell(priv, false); > } > > +static int tpm_crb_send_chunks(struct tpm_chip *chip, u8 *buf, size_t len) > +{ > + struct crb_priv *priv = dev_get_drvdata(&chip->dev); > + size_t chunk_size; > + size_t offset = 0; > + int rc; > + bool expired; > + > + while (offset < len) { > + chunk_size = min_t(size_t, len - offset, priv->cmd_size); > + if (chunk_size == 0) > + break; > + > + memcpy_toio(priv->cmd, buf + offset, chunk_size); > + offset += chunk_size; > + > + /* Make sure that cmd is populated before issuing start. */ > + wmb(); > + > + if (offset < len) { > + rc = tpm_crb_start(chip, CRB_START_NEXT_CHUNK); > + if (rc) > + return rc; > + expired = > !crb_wait_for_reg_32(&priv->regs_t->ctrl_start, > + CRB_START_NEXT_CHUNK, 0, > + TPM2_TIMEOUT_C); > + if (expired) { > + dev_err(&chip->dev, > + "Timeout waiting for backend to consume > chunk\n"); > + return -ETIME; > + } > + } else { > + rc = tpm_crb_start(chip, CRB_START_INVOKE); > + if (rc) > + return rc; > + } > + } > + return crb_try_pluton_doorbell(priv, false); > +} > + > static int crb_send(struct tpm_chip *chip, u8 *buf, size_t bufsiz, size_t > len) > { > struct crb_priv *priv = dev_get_drvdata(&chip->dev); > @@ -512,7 +613,7 @@ static int crb_send(struct tpm_chip *chip, u8 *buf, > size_t bufsiz, size_t len) > */ > iowrite32(0, &priv->regs_t->ctrl_cancel); > > - if (len > priv->cmd_size) { > + if (len > priv->cmd_size && !(priv->intf_id & CRB_INTF_CAP_CRB_CHUNK)) { > dev_err(&chip->dev, "invalid command count value %zd %d\n", > len, priv->cmd_size); > return -E2BIG; > @@ -522,7 +623,10 @@ static int crb_send(struct tpm_chip *chip, u8 *buf, > size_t bufsiz, size_t len) > if (priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_PLUTON) > __crb_cmd_ready(&chip->dev, priv, chip->locality); > > - return tpm_crb_send_no_chunks(chip, buf, len); > + if (len <= priv->cmd_size) > + return tpm_crb_send_no_chunks(chip, buf, len); > + > + return tpm_crb_send_chunks(chip, buf, len); > } > > static void crb_cancel(struct tpm_chip *chip) > @@ -748,6 +852,11 @@ static int crb_map_io(struct device *dev, struct > crb_priv *priv, > ret = PTR_ERR(priv->cmd); > goto out; > } > + if (priv->regs_h) > + priv->intf_id = ioread32((u32 __iomem *)&priv->regs_h->intf_id); > + > + if (priv->intf_id & CRB_INTF_CAP_CRB_CHUNK) > + dev_info(dev, "CRB Chunking is supported by backend\n"); > > memcpy_fromio(&__rsp_pa, &priv->regs_t->ctrl_rsp_pa, 8); > rsp_pa = le64_to_cpu(__rsp_pa); > @@ -786,8 +895,10 @@ static int crb_map_io(struct device *dev, struct > crb_priv *priv, > priv->rsp = priv->cmd; > > out: > - if (!ret) > + if (!ret) { > priv->cmd_size = cmd_size; > + priv->rsp_size = rsp_size; > + } > > __crb_go_idle(dev, priv, 0); > > -- > 2.56.0 >
Reviewed-by: Jarkko Sakkinen <[email protected]> Br, Jarkko
