linux-kernel - Re: [PATCH v3 3/8] x86/psp: Register PSP platform device when ASP table is present

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Message-ID: <20230320192504.GCZBizEGDjVtGWpNP3@fat_crate.local>
Date:   Mon, 20 Mar 2023 20:25:04 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Jeremi Piotrowski <jpiotrowski@...ux.microsoft.com>
Cc:     linux-kernel@...r.kernel.org,
        Brijesh Singh <brijesh.singh@....com>,
        Tom Lendacky <thomas.lendacky@....com>,
        "Kalra, Ashish" <ashish.kalra@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org
Subject: Re: [PATCH v3 3/8] x86/psp: Register PSP platform device when ASP
 table is present

On Mon, Mar 20, 2023 at 07:19:51PM +0000, Jeremi Piotrowski wrote:
> The ASP table contains the memory location of the register window for
> communication with the Platform Security Processor. The device is not
> exposed as an acpi node, so it is necessary to probe for the table and
> register a platform_device to represent it in the kernel.
> 
> At least conceptually, the same PSP may be exposed on the PCIe bus as
> well, in which case it would be necessary to choose whether to use a PCI
> BAR or the register window defined in ASPT for communication. There is
> no advantage to using the ACPI and there are no known bare-metal systems
> that expose the ASP table, so device registration is restricted to the
> only systems known to provide an ASPT: Hyper-V VMs. Hyper-V VMs also do
> not expose the PSP over PCIe.
> 
> This is a skeleton device at this point, as the ccp driver is not yet
> prepared to correctly probe it. Interrupt configuration will come later
> on as well.
> 
> Acked-by: Tom Lendacky <thomas.lendacky@....com>
> Signed-off-by: Jeremi Piotrowski <jpiotrowski@...ux.microsoft.com>
> ---
>  arch/x86/kernel/Makefile |  1 +
>  arch/x86/kernel/psp.c    | 42 ++++++++++++++++++++++++++++++++++++++++

If this is a platform device (driver), why isn't it part of
the drivers/platform/x86/ lineup?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette