linux-kernel - Re: [PATCH v6 4/4] x86/sev: register tpm-svsm platform device

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Message-ID: <CAGxU2F7r_fWgr2YRmCvh2iQ1vPg30f-+W6FXyuidbakZkwhw2w@mail.gmail.com>
Date: Wed, 9 Apr 2025 12:43:01 +0200
From: Stefano Garzarella <sgarzare@...hat.com>
To: Borislav Petkov <bp@...en8.de>
Cc: Jarkko Sakkinen <jarkko@...nel.org>, Dave Hansen <dave.hansen@...ux.intel.com>, 
	Peter Huewe <peterhuewe@....de>, Jason Gunthorpe <jgg@...pe.ca>, "H. Peter Anvin" <hpa@...or.com>, 
	linux-coco@...ts.linux.dev, linux-integrity@...r.kernel.org, 
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org, Tom Lendacky <thomas.lendacky@....com>, 
	Joerg Roedel <jroedel@...e.de>, Dionna Glaze <dionnaglaze@...gle.com>, 
	Claudio Carvalho <cclaudio@...ux.ibm.com>, 
	James Bottomley <James.Bottomley@...senpartnership.com>, linux-kernel@...r.kernel.org, 
	Dov Murik <dovmurik@...ux.ibm.com>, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v6 4/4] x86/sev: register tpm-svsm platform device

On Wed, 9 Apr 2025 at 12:21, Borislav Petkov <bp@...en8.de> wrote:
>
> On Tue, Apr 08, 2025 at 01:54:07PM +0200, Stefano Garzarella wrote:
> > I see, so IIUC I can just apply the following change to this patch and avoid
> > to export snp_svsm_vtpm_probe() at all, right?
> >
> > diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
> > index acbd9bc526b1..fa83e6c7f990 100644
> > --- a/arch/x86/coco/sev/core.c
> > +++ b/arch/x86/coco/sev/core.c
> > @@ -2702,8 +2702,10 @@ static int __init snp_init_platform_device(void)
> >         if (platform_device_register(&sev_guest_device))
> >                 return -ENODEV;
> > -       if (platform_device_register(&tpm_svsm_device))
> > -               return -ENODEV;
> > +       if (snp_svsm_vtpm_probe()) {
> > +               if (platform_device_register(&tpm_svsm_device))
> > +                       return -ENODEV;
> > +       }
> >         pr_info("SNP guest platform device initialized.\n");
> >         return 0;
>
> No, this should go in tpm_svsm_probe().

Sorry, maybe I missed something.

tpm_svsm.c registers the driver with module_platform_driver_probe().

Someone (the platform I guess) has to register the device by calling
platform_device_register(), as we already do for example for
sev_guest.

If we move platform_device_register() to tpm_svsm_probe() how will the
probe be invoked?

Thanks,
Stefano