linux-kernel - Re: [PATCH 3/3] x86/sev: add a SVSM vTPM platform device

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Message-ID: <20241211150048.GJ1888283@ziepe.ca>
Date: Wed, 11 Dec 2024 11:00:48 -0400
From: Jason Gunthorpe <jgg@...pe.ca>
To: Stefano Garzarella <sgarzare@...hat.com>
Cc: James Bottomley <James.Bottomley@...senpartnership.com>,
	linux-coco@...ts.linux.dev, Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Peter Huewe <peterhuewe@....de>, "H. Peter Anvin" <hpa@...or.com>,
	linux-integrity@...r.kernel.org, x86@...nel.org,
	Joerg Roedel <jroedel@...e.de>, Jarkko Sakkinen <jarkko@...nel.org>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Claudio Carvalho <cclaudio@...ux.ibm.com>,
	Dov Murik <dovmurik@...ux.ibm.com>,
	Tom Lendacky <thomas.lendacky@....com>
Subject: Re: [PATCH 3/3] x86/sev: add a SVSM vTPM platform device

On Wed, Dec 11, 2024 at 09:19:04AM +0100, Stefano Garzarella wrote:

> > After that, there is no meaningful shared code here, and maybe the
> > TPM_CHIP_FLAG_IRQ hack can be avoided too.
> 
> IIUC you are proposing the following steps:
> - extend tpm_class_ops to add a new send_recv() op and use it in
> tpm_try_transmit()

Yes, that seems to be the majority of your shared code.

> - call the code in tpm_platform_probe() directly in sev

Yes

> This would remove the intermediate driver, but at this point is it
> worth keeping tpm_platform_send() and tpm_platform_recv() in a header
> or module, since these are not related to sev, but to MSSIM?

Reuse *what* exactly? These are 10 both line funtions that just call
another function pointer. Where exactly is this common MSSIM stuff?

Stated another way, by adding send_Recv() op to tpm_class_ops you have
already allowed reuse of all the code in tpm_platform_send/recv().

Jason