linux-kernel - Re: [PATCH 4/5] platform/x86/intel/ifs: Implement Array BIST test

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Date:   Wed, 1 Feb 2023 06:02:17 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Jithu Joseph <jithu.joseph@...el.com>
Cc:     hdegoede@...hat.com, markgross@...nel.org, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        x86@...nel.org, hpa@...or.com, rostedt@...dmis.org,
        ashok.raj@...el.com, tony.luck@...el.com,
        linux-kernel@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        patches@...ts.linux.dev, ravi.v.shankar@...el.com,
        thiago.macieira@...el.com, athenas.jimenez.gonzalez@...el.com,
        sohil.mehta@...el.com
Subject: Re: [PATCH 4/5] platform/x86/intel/ifs: Implement Array BIST test

On Tue, Jan 31, 2023 at 03:43:01PM -0800, Jithu Joseph wrote:
> Array BIST test (for a particlular core) is triggered by writing
> to MSR_ARRAY_BIST from one sibling of the core.
> 
> This will initiate a test for all supported arrays on that
> CPU. Array BIST test may be aborted before completing all the
> arrays in the event of an interrupt or other reasons.
> In this case, kernel will restart the test from that point
> onwards. Array test will also be aborted when the test fails,
> in which case the test is stopped immediately without further
> retry.
> 
> Signed-off-by: Jithu Joseph <jithu.joseph@...el.com>
> Reviewed-by: Tony Luck <tony.luck@...el.com>
> ---
>  drivers/platform/x86/intel/ifs/ifs.h     | 12 ++++
>  drivers/platform/x86/intel/ifs/runtest.c | 92 ++++++++++++++++++++++++
>  2 files changed, 104 insertions(+)
> 
> diff --git a/drivers/platform/x86/intel/ifs/ifs.h b/drivers/platform/x86/intel/ifs/ifs.h
> index 07423bc4e368..b1a997e39216 100644
> --- a/drivers/platform/x86/intel/ifs/ifs.h
> +++ b/drivers/platform/x86/intel/ifs/ifs.h
> @@ -127,6 +127,7 @@
>  #include <linux/device.h>
>  #include <linux/miscdevice.h>
>  
> +#define MSR_ARRAY_BIST				0x00000105
>  #define MSR_COPY_SCAN_HASHES			0x000002c2
>  #define MSR_SCAN_HASHES_STATUS			0x000002c3
>  #define MSR_AUTHENTICATE_AND_COPY_CHUNK		0x000002c4
> @@ -194,6 +195,17 @@ union ifs_status {
>  	};
>  };
>  
> +/* MSR_ARRAY_BIST bit fields */
> +union ifs_array {
> +	u64	data;
> +	struct {
> +		u32	array_bitmask		:32;
> +		u32	array_bank		:16;
> +		u32	rsvd			:15;
> +		u32	ctrl_result		:1;

This isn't going to work well over time, just mask the bits you want off
properly, don't rely on the compiler to lay them out like this.

Note, we have bitmask and bitfield operations, please use them.

thanks,

greg k-h