linux-kernel - Re: [PATCH v5 4/4] tpm/tpm_svsm: support TPM_CHIP_FLAG

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Message-ID: <CAGxU2F5AsNY5mQPd=qajW1seFYHSYpB0Fa1iuR_f2QavtoB6sA@mail.gmail.com>
Date: Tue, 20 May 2025 18:06:50 +0200
From: Stefano Garzarella <sgarzare@...hat.com>
To: Jarkko Sakkinen <jarkko@...nel.org>
Cc: linuxppc-dev@...ts.ozlabs.org, Peter Huewe <peterhuewe@....de>, 
	Jens Wiklander <jens.wiklander@...aro.org>, linux-integrity@...r.kernel.org, 
	Alexandre Belloni <alexandre.belloni@...tlin.com>, linux-arm-kernel@...ts.infradead.org, 
	Nicolas Ferre <nicolas.ferre@...rochip.com>, Nicholas Piggin <npiggin@...il.com>, 
	Sumit Garg <sumit.garg@...nel.org>, 
	James Bottomley <James.Bottomley@...senpartnership.com>, 
	Claudiu Beznea <claudiu.beznea@...on.dev>, Madhavan Srinivasan <maddy@...ux.ibm.com>, 
	Jason Gunthorpe <jgg@...pe.ca>, linux-kernel@...r.kernel.org, 
	Christophe Leroy <christophe.leroy@...roup.eu>, Naveen N Rao <naveen@...nel.org>, 
	Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH v5 4/4] tpm/tpm_svsm: support TPM_CHIP_FLAG_SYNC

On Thu, 15 May 2025 at 03:45, Jarkko Sakkinen <jarkko@...nel.org> wrote:
>
> On Wed, May 14, 2025 at 03:46:30PM +0200, Stefano Garzarella wrote:
> > From: Stefano Garzarella <sgarzare@...hat.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@...hat.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!

Stefano