[PATCH v5 4/4] tpm/tpm_svsm: support TPM_CHIP_FLAG_SYNC

[Jarkko Sakkinen]

On Tue, May 20, 2025 at 06:06:50PM +0200, Stefano Garzarella wrote:
> On Thu, 15 May 2025 at 03:45, Jarkko Sakkinen <jarkko at kernel.org> wrote:
> >
> > On Wed, May 14, 2025 at 03:46:30PM +0200, Stefano Garzarella wrote:
> > > From: Stefano Garzarella <sgarzare at redhat.com>
> > >
> > > 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 at redhat.com>
> > > ---
> > > v5:
> > > - changed order and parameter names to match tpm_try_transmit() [Jarkko]
> > > v4:
> > > - reworked commit description [Jarkko]
> > > ---
> > >  drivers/char/tpm/tpm_svsm.c | 27 +++++++++++----------------
> > >  1 file changed, 11 insertions(+), 16 deletions(-)
> > >
> > > diff --git a/drivers/char/tpm/tpm_svsm.c b/drivers/char/tpm/tpm_svsm.c
> > > index 0847cbf450b4..f5ba0f64850b 100644
> > > --- a/drivers/char/tpm/tpm_svsm.c
> > > +++ b/drivers/char/tpm/tpm_svsm.c
> > > @@ -26,37 +26,31 @@ struct tpm_svsm_priv {
> > >  };
> > >
> > >  static int tpm_svsm_send(struct tpm_chip *chip, u8 *buf, size_t bufsiz,
> > > -                      size_t len)
> > > +                      size_t cmd_len)
> > >  {
> > >       struct tpm_svsm_priv *priv = dev_get_drvdata(&chip->dev);
> > >       int ret;
> > >
> > > -     ret = svsm_vtpm_cmd_request_fill(priv->buffer, 0, buf, len);
> > > +     ret = svsm_vtpm_cmd_request_fill(priv->buffer, 0, buf, cmd_len);
> > >       if (ret)
> > >               return ret;
> > >
> > >       /*
> > >        * The SVSM call uses the same buffer for the command and for the
> > > -      * response, so after this call, the buffer will contain the response
> > > -      * that can be used by .recv() op.
> > > +      * response, so after this call, the buffer will contain the response.
> > > +      *
> > > +      * Note: we have to use an internal buffer because the device in SVSM
> > > +      * expects the svsm_vtpm header + data to be physically contiguous.
> > >        */
> > > -     return snp_svsm_vtpm_send_command(priv->buffer);
> > > -}
> > > -
> > > -static int tpm_svsm_recv(struct tpm_chip *chip, u8 *buf, size_t len)
> > > -{
> > > -     struct tpm_svsm_priv *priv = dev_get_drvdata(&chip->dev);
> > > +     ret = snp_svsm_vtpm_send_command(priv->buffer);
> > > +     if (ret)
> > > +             return ret;
> > >
> > > -     /*
> > > -      * The internal buffer contains the response after we send the command
> > > -      * to SVSM.
> > > -      */
> > > -     return svsm_vtpm_cmd_response_parse(priv->buffer, buf, len);
> > > +     return svsm_vtpm_cmd_response_parse(priv->buffer, buf, bufsiz);
> > >  }
> > >
> > >  static struct tpm_class_ops tpm_chip_ops = {
> > >       .flags = TPM_OPS_AUTO_STARTUP,
> > > -     .recv = tpm_svsm_recv,
> > >       .send = tpm_svsm_send,
> > >  };
> > >
> > > @@ -85,6 +79,7 @@ static int __init tpm_svsm_probe(struct platform_device *pdev)
> > >
> > >       dev_set_drvdata(&chip->dev, priv);
> > >
> > > +     chip->flags |= TPM_CHIP_FLAG_SYNC;
> > >       err = tpm2_probe(chip);
> > >       if (err)
> > >               return err;
> > > --
> > > 2.49.0
> > >
> > >
> >
> > I can pick this for 6.16.
> 
> Great, thanks!

Can you rebase this on top of my next branch and send one more version
of the series (fake ancestor crap)?

> 
> Stefano
> 

BR, Jarkko