| Message ID | 20211225123806.113368-1-ykonotopov@gnome.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | tpm: fixed be_buffer_size size in in tpm_crb | expand |
+Marc-André On 12/25/21 13:38, Yuri Konotopov wrote: > Trying to boot VM with TPM 2.0 CRB in passthrough mode without this change > I got "Requested buffer size of 3968 is smaller than host TPM's fixed > buffer size of 4096". > Looks like it can not be less than backend buffer size nor less than > CRB_CTRL_CMD_SIZE. > > Signed-off-by: Yuri Konotopov <ykonotopov@gnome.org> > --- > hw/tpm/tpm_crb.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/hw/tpm/tpm_crb.c b/hw/tpm/tpm_crb.c > index 58ebd1469c..8243645453 100644 > --- a/hw/tpm/tpm_crb.c > +++ b/hw/tpm/tpm_crb.c > @@ -270,7 +270,7 @@ static void tpm_crb_reset(void *dev) > s->regs[R_CRB_CTRL_RSP_SIZE] = CRB_CTRL_CMD_SIZE; > s->regs[R_CRB_CTRL_RSP_ADDR] = TPM_CRB_ADDR_BASE + A_CRB_DATA_BUFFER; > > - s->be_buffer_size = MIN(tpm_backend_get_buffer_size(s->tpmbe), > + s->be_buffer_size = MAX(tpm_backend_get_buffer_size(s->tpmbe), > CRB_CTRL_CMD_SIZE); > > if (tpm_backend_startup_tpm(s->tpmbe, s->be_buffer_size) < 0) { This doesn't look correct: if the backend buffer size is smaller, we can not use a bigger size, otherwise we might end up overflowing the buffer. What about checking the backend buffer size at realization? Could the backend change this size on reset? -- >8 -- diff --git a/hw/tpm/tpm_crb.c b/hw/tpm/tpm_crb.c index 58ebd1469c3..57346eaa857 100644 --- a/hw/tpm/tpm_crb.c +++ b/hw/tpm/tpm_crb.c @@ -270,9 +270,6 @@ static void tpm_crb_reset(void *dev) s->regs[R_CRB_CTRL_RSP_SIZE] = CRB_CTRL_CMD_SIZE; s->regs[R_CRB_CTRL_RSP_ADDR] = TPM_CRB_ADDR_BASE + A_CRB_DATA_BUFFER; - s->be_buffer_size = MIN(tpm_backend_get_buffer_size(s->tpmbe), - CRB_CTRL_CMD_SIZE); - if (tpm_backend_startup_tpm(s->tpmbe, s->be_buffer_size) < 0) { exit(1); } @@ -290,6 +287,12 @@ static void tpm_crb_realize(DeviceState *dev, Error **errp) error_setg(errp, "'tpmdev' property is required"); return; } + s->be_buffer_size = tpm_backend_get_buffer_size(s->tpmbe); + if (s->be_buffer_size < CRB_CTRL_CMD_SIZE) { + error_setg(errp, "'tpmdev' buffer size too small (%zu, minimum: %u)", + s->be_buffer_size, CRB_CTRL_CMD_SIZE); + return; + } memory_region_init_io(&s->mmio, OBJECT(s), &tpm_crb_memory_ops, s, "tpm-crb-mmio", sizeof(s->regs)); ---
On 12/25/21 07:38, Yuri Konotopov wrote: > Trying to boot VM with TPM 2.0 CRB in passthrough mode without this change > I got "Requested buffer size of 3968 is smaller than host TPM's fixed > buffer size of 4096". I suppose the host has a TIS interface. The reason it gives this message is that the response this TPM may send back could be 4096 bytes in size but the CRB of the VM can only catch 3968 bytes, so there's a mismatch. You may not be able to use the CRB in passthrough mode. I would try to have the VM use the TIS. Stefan > Looks like it can not be less than backend buffer size nor less than > CRB_CTRL_CMD_SIZE. > > Signed-off-by: Yuri Konotopov <ykonotopov@gnome.org> > --- > hw/tpm/tpm_crb.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/hw/tpm/tpm_crb.c b/hw/tpm/tpm_crb.c > index 58ebd1469c..8243645453 100644 > --- a/hw/tpm/tpm_crb.c > +++ b/hw/tpm/tpm_crb.c > @@ -270,7 +270,7 @@ static void tpm_crb_reset(void *dev) > s->regs[R_CRB_CTRL_RSP_SIZE] = CRB_CTRL_CMD_SIZE; > s->regs[R_CRB_CTRL_RSP_ADDR] = TPM_CRB_ADDR_BASE + A_CRB_DATA_BUFFER; > > - s->be_buffer_size = MIN(tpm_backend_get_buffer_size(s->tpmbe), > + s->be_buffer_size = MAX(tpm_backend_get_buffer_size(s->tpmbe), > CRB_CTRL_CMD_SIZE); > > if (tpm_backend_startup_tpm(s->tpmbe, s->be_buffer_size) < 0) {
On 12/26/21 21:24, Stefan Berger wrote: > > On 12/25/21 07:38, Yuri Konotopov wrote: >> Trying to boot VM with TPM 2.0 CRB in passthrough mode without this >> change >> I got "Requested buffer size of 3968 is smaller than host TPM's fixed >> buffer size of 4096". > > I suppose the host has a TIS interface. > > The reason it gives this message is that the response this TPM may > send back could be 4096 bytes in size but the CRB of the VM can only > catch 3968 bytes, so there's a mismatch. You may not be able to use > the CRB in passthrough mode. I would try to have the VM use the TIS. For TPM passthrough the host TPM's buffer size basically has to match the VM's buffer size so that - apps inside the VM cannot create longer commands than what the host device can accept - apps inside the VM cannot create commands that cause the TPM to return responses that are bigger than what the VM's TPM buffer can accept Stefan
27.12.2021 06:24, Stefan Berger пишет: > I suppose the host has a TIS interface. Hello, Stefan. I do not think so. There is only tpm_crb tpm kernel module compiled in my system # systemd-cryptenroll --tpm2-device=list PATH DEVICE DRIVER /dev/tpmrm0 MSFT0101:00 tpm_crb > > The reason it gives this message is that the response this TPM may > send back could be 4096 bytes in size but the CRB of the VM can only > catch 3968 bytes, so there's a mismatch. You may not be able to use > the CRB in passthrough mode. I would try to have the VM use the TIS.
diff --git a/hw/tpm/tpm_crb.c b/hw/tpm/tpm_crb.c index 58ebd1469c..8243645453 100644 --- a/hw/tpm/tpm_crb.c +++ b/hw/tpm/tpm_crb.c @@ -270,7 +270,7 @@ static void tpm_crb_reset(void *dev) s->regs[R_CRB_CTRL_RSP_SIZE] = CRB_CTRL_CMD_SIZE; s->regs[R_CRB_CTRL_RSP_ADDR] = TPM_CRB_ADDR_BASE + A_CRB_DATA_BUFFER; - s->be_buffer_size = MIN(tpm_backend_get_buffer_size(s->tpmbe), + s->be_buffer_size = MAX(tpm_backend_get_buffer_size(s->tpmbe), CRB_CTRL_CMD_SIZE); if (tpm_backend_startup_tpm(s->tpmbe, s->be_buffer_size) < 0) {
Trying to boot VM with TPM 2.0 CRB in passthrough mode without this change I got "Requested buffer size of 3968 is smaller than host TPM's fixed buffer size of 4096". Looks like it can not be less than backend buffer size nor less than CRB_CTRL_CMD_SIZE. Signed-off-by: Yuri Konotopov <ykonotopov@gnome.org> --- hw/tpm/tpm_crb.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)