From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B815B21325A; Thu, 27 Mar 2025 11:53:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743076439; cv=none; b=RXxM+MHzGVR8YsmWCc1mx3IfKsQGde3v8aeAjdhvpWOKe3QtFDcHQ2layyfXYL0wdZR1pDOxEdO/e+fRpMdYXwWOOwBI6lw+tMtE5MVOdZBcwf0XZc1LRsOI8Dkx4oeF4YqtqCCRn3nbRy2TptBH9+vDauiga9YbRQ+hdl+PlqE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743076439; c=relaxed/simple; bh=NchHAJlPW5YBoy+sbFXJsNxaHec074HCzzirreu6RGE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=PqF7nGb2bH+N/APgQ6SLHp3tTXvYwWa13ZhBTSF9T9ndqujaTdyESDVJc7fUlfL2nMit1r7wsYW9ME0X15s6TtgXCTvCEQcnxFeQJLDGLLJWcJIXqRt97F8N9uoVgHeJe9kII+ZqCXiKZS+9Es12iVovaXDDpS2kjMonmtf/FH8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=EqCOQlJ9; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="EqCOQlJ9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D347DC4CEDD; Thu, 27 Mar 2025 11:53:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1743076439; bh=NchHAJlPW5YBoy+sbFXJsNxaHec074HCzzirreu6RGE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=EqCOQlJ9ZRsHN9ixfoPHIAE2jM6VclPNEQaDQMYYpvZSxGW5B+EfFzwHYDs5fc4Y3 8iN4RUyGjTTIoq7st4cwGXmgiz2fgZ4dkWWgdu6fVRe2w13OuZyUj4A29fNkS3XjQ6 sNSgGqDEI0qUrTS9xECfOlGH7sfR+Htojrti9Ffz4LVTgXCduagVMN58/Kcfy0SjYN 13sO41IOj33ak7st/F2PcDnYmbGv1Uf5RyXihsAvOu8+xBnCzB0CJiIq8rmvF1FCv1 gh31HvILg1Pzh+YrYYbmMZi1Q385pTklwf1IgLQBwDIKeR3w1FAsEaY6yfx13YyI9U mehva9pBJYKIg== Date: Thu, 27 Mar 2025 13:53:55 +0200 From: Jarkko Sakkinen To: Stefano Garzarella Cc: Joerg Roedel , Ingo Molnar , Dave Hansen , Peter Huewe , Tom Lendacky , Thomas Gleixner , x86@kernel.org, James Bottomley , linux-kernel@vger.kernel.org, Borislav Petkov , Jason Gunthorpe , "H. Peter Anvin" , linux-coco@lists.linux.dev, Claudio Carvalho , Dov Murik , Dionna Glaze , linux-integrity@vger.kernel.org Subject: Re: [PATCH v4 3/4] tpm: add SNP SVSM vTPM driver Message-ID: References: <20250324104653.138663-1-sgarzare@redhat.com> <20250324104653.138663-4-sgarzare@redhat.com> Precedence: bulk X-Mailing-List: linux-integrity@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Mar 27, 2025 at 11:03:07AM +0100, Stefano Garzarella wrote: > On Wed, Mar 26, 2025 at 09:30:53PM +0200, Jarkko Sakkinen wrote: > > On Mon, Mar 24, 2025 at 11:46:48AM +0100, Stefano Garzarella wrote: > > > From: Stefano Garzarella > > > > > > 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 two functions exposed by x86/sev > > > to verify that the device is actually emulated by the platform and to > > > send commands and receive responses. > > > > > > The device cannot be hot-plugged/unplugged as it is emulated by the > > > platform, so we can use module_platform_driver_probe(). The probe > > > function will only check whether in the current runtime configuration, > > > SVSM is present and provides a vTPM. > > > > > > 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 returns 0, and both > > > .req_complete_mask and .req_complete_val are set to 0. > > > > > > [1] "Secure VM Service Module for SEV-SNP Guests" > > > Publication # 58019 Revision: 1.00 > > > > > > Signed-off-by: Stefano Garzarella > > > --- > > > v4: > > > - moved "asm" includes after the "linux" includes [Tom] > > > - allocated buffer separately [Tom/Jarkko/Jason] > > > v3: > > > - removed send_recv() ops and followed the ftpm driver implementing .status, > > > .req_complete_mask, .req_complete_val, etc. [Jarkko] > > > - removed link to the spec because those URLs are unstable [Borislav] > > > --- > > > drivers/char/tpm/tpm_svsm.c | 155 ++++++++++++++++++++++++++++++++++++ > > > drivers/char/tpm/Kconfig | 10 +++ > > > drivers/char/tpm/Makefile | 1 + > > > 3 files changed, 166 insertions(+) > > > create mode 100644 drivers/char/tpm/tpm_svsm.c > > > > > > diff --git a/drivers/char/tpm/tpm_svsm.c b/drivers/char/tpm/tpm_svsm.c > > > new file mode 100644 > > > index 000000000000..1281ff265927 > > > --- /dev/null > > > +++ b/drivers/char/tpm/tpm_svsm.c > > > @@ -0,0 +1,155 @@ > > > +// SPDX-License-Identifier: GPL-2.0-only > > > +/* > > > + * Copyright (C) 2025 Red Hat, Inc. All Rights Reserved. > > > + * > > > + * 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 (usually VMPL0). > > > + * > > > + * [1] "Secure VM Service Module for SEV-SNP Guests" > > > + * Publication # 58019 Revision: 1.00 > > > + */ > > > + > > > +#include > > > +#include > > > +#include > > > +#include > > > + > > > +#include > > > + > > > +#include "tpm.h" > > > + > > > +struct tpm_svsm_priv { > > > + void *buffer; > > > + u8 locality; > > > +}; > > > + > > > +static int tpm_svsm_send(struct tpm_chip *chip, u8 *buf, size_t len) > > > +{ > > > + struct tpm_svsm_priv *priv = dev_get_drvdata(&chip->dev); > > > + int ret; > > > + > > > + ret = svsm_vtpm_cmd_request_fill(priv->buffer, priv->locality, buf, 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. > > > + */ > > > + 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); > > > + > > > + /* > > > + * The internal buffer contains the response after we send the command > > > + * to SVSM. > > > + */ > > > + return svsm_vtpm_cmd_response_parse(priv->buffer, buf, len); > > > +} > > > + > > > +static void tpm_svsm_cancel(struct tpm_chip *chip) > > > +{ > > > + /* not supported */ > > > +} > > > + > > > +static u8 tpm_svsm_status(struct tpm_chip *chip) > > > +{ > > > + return 0; > > > +} > > > + > > > +static bool tpm_svsm_req_canceled(struct tpm_chip *chip, u8 status) > > > +{ > > > + return false; > > > +} > > > + > > > +static struct tpm_class_ops tpm_chip_ops = { > > > + .flags = TPM_OPS_AUTO_STARTUP, > > > + .recv = tpm_svsm_recv, > > > + .send = tpm_svsm_send, > > > + .cancel = tpm_svsm_cancel, > > > + .status = tpm_svsm_status, > > > + .req_complete_mask = 0, > > > + .req_complete_val = 0, > > > + .req_canceled = tpm_svsm_req_canceled, > > > > If this was bundled with the patch set, this would short a lot: > > > > https://lore.kernel.org/linux-integrity/20250326161838.123606-1-jarkko@kernel.org/T/#u > > > > So maybe for v5? Including this patch does not take send_recv() > > out of consideration, it is just smart thing to do in all cases. > > > > It would be probably easiest to roll out my patch together with > > rest of the patch set. > > Yeah, I agree. I'll include it in this series and adapt this patch on top of > it. Yeah, and you could simplify to goal in the other patch set: it's about avoiding double-copy of a buffer. It's a totally legit argument that we can measure. So in the end this will help out landing that too because it takes away the extra cruft and streamlines the goal. > > Thanks, > Stefano > > BR, Jarkko