linux-kernel - Re: [PATCH v6 12/14] platform/x86: dell-smbios-smm: test for WSMT

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Date:   Tue, 10 Oct 2017 21:11:09 +0200
From:   Pali Rohár <pali.rohar@...il.com>
To:     Mario Limonciello <mario.limonciello@...l.com>
Cc:     dvhart@...radead.org, Andy Shevchenko <andy.shevchenko@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        platform-driver-x86@...r.kernel.org,
        Andy Lutomirski <luto@...nel.org>, quasisec@...gle.com,
        rjw@...ysocki.net, mjg59@...gle.com, hch@....de,
        Greg KH <greg@...ah.com>
Subject: Re: [PATCH v6 12/14] platform/x86: dell-smbios-smm: test for WSMT

On Monday 09 October 2017 17:51:50 Mario Limonciello wrote:
> WSMT is as an attestation to the OS that the platform won't
> modify memory outside of pre-defined areas.
> 
> If a platform has WSMT enabled in BIOS setup, SMM calls through
> dcdbas will fail.  The only way to access platform data in these
> instances is through the WMI SMBIOS calling interface.
> 
> Signed-off-by: Mario Limonciello <mario.limonciello@...l.com>
> ---
>  drivers/platform/x86/dell-smbios-smm.c | 34 ++++++++++++++++++++++++++++++++++
>  1 file changed, 34 insertions(+)
> 
> diff --git a/drivers/platform/x86/dell-smbios-smm.c b/drivers/platform/x86/dell-smbios-smm.c
> index 223531e43fea..ba315753e847 100644
> --- a/drivers/platform/x86/dell-smbios-smm.c
> +++ b/drivers/platform/x86/dell-smbios-smm.c
> @@ -25,6 +25,8 @@ static struct calling_interface_buffer *buffer;
>  struct platform_device *platform_device;
>  static DEFINE_MUTEX(smm_mutex);
>  
> +#define WSMT_EN_TOKEN	0x04EC

Maybe there should be some comment in code what does this WSMT
abbreviation mean...

>  static const struct dmi_system_id dell_device_table[] __initconst = {
>  	{
>  		.ident = "Dell laptop",

-- 
Pali Rohár
pali.rohar@...il.com