This driver does not support interrupts, and receiving the response is
synchronous with sending the command.
Enable synchronous send() with TPM_CHIP_FLAG_SYNC, which implies that
->send() already fills the provided buffer with a response, and ->recv()
is not implemented.
Keep using the same pre-allocated buffer to avoid having to allocate
it for each command. We need the buffer to have the header required by
the SVSM protocol and the command contiguous in memory.
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Add a new `bufsiz` parameter to the `.send` callback in `tpm_class_ops`.
This parameter will allow drivers to differentiate between the actual
command length to send and the total buffer size. Currently `bufsiz` is
not used, but it will be used to implement devices with synchronous send()
to send the command and receive the response on the same buffer.
Also rename the previous parameter `len` to `cmd_len` in the declaration
to make it clear that it contains the length in bytes of the command
stored in the buffer. The semantics don't change and it can be used as
before by drivers. This is an optimization since the drivers could get it
from the header, but let's avoid duplicating code.
While we are here, resolve a checkpatch warning:
WARNING: Unnecessary space before function pointer arguments
#66: FILE: include/linux/tpm.h:90:
+ int (*send) (struct tpm_chip *chip, u8 *buf, size_t bufsiz,
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Suggested-by: Jarkko Sakkinen <jarkko@kernel.org>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Add driver for the vTPM defined by the AMD SVSM spec [1].
The specification defines a protocol that a SEV-SNP guest OS can use to
discover and talk to a vTPM emulated by the Secure VM Service Module (SVSM) in
the guest context, but at a more privileged level (VMPL0).
The new tpm-svsm platform driver uses API exposed by the x86/sev core
implementation interface to a SVSM to send commands and receive responses.
The device cannot be hot-plugged/unplugged as it is emulated by the platform,
so module_platform_driver_probe() can be used. The device will be registered
by the platform only when it's available, so the probe function just needs to
setup the tpm_chip.
This device does not support interrupts and sends responses to commands
synchronously.
In order to have .recv() called just after .send() in tpm_try_transmit(), the
.status() callback is not implemented as recently supported by commit
980a573621 ("tpm: Make chip->{status,cancel,req_canceled} opt").
[1] "Secure VM Service Module for SEV-SNP Guests"
Publication # 58019 Revision: 1.00
[ bp: Massage commit message. ]
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Link: https://lore.kernel.org/r/20250410135118.133240-4-sgarzare@redhat.com
