linux-kernel - Re: [PATCH -v2] x86: Add an archinfo dumper module

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Date:	Thu, 4 Feb 2016 11:07:57 -0800
From:	"Luck, Tony" <tony.luck@...el.com>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Ingo Molnar <mingo@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andy Lutomirski <luto@...capital.net>,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Brian Gerst <brgerst@...il.com>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -v2] x86: Add an archinfo dumper module

On Thu, Feb 04, 2016 at 04:22:35PM +0100, Borislav Petkov wrote:
> Here's v2 with the stuff we talked about, implemented. I've added
> 'control_regs' file too so that you can do:
> 
> $ cat /sys/kernel/debug/x86/archinfo/control_regs
> CR4: [-|-|SMEP|OSXSAVE|-|-|-|-|OSXMMEXCPT|OSFXSR|-|PGE|MCE|PAE|PSE|-|-|-|-]: 0x1406f0
> 
> for example. Yeah, only CR4 right now.
> 
> Off the top of my head, we would need "msrs" which dumps EFER and a
> bunch of other interesting MSRs along with the names of the set bits.

It would be nce to have some helper function that makes it easier for
people to add new registers to this that just uses one string
to describe the format of a register.  E.g. if we have a register
like this:

	 63 63 62  11 10  9 8    5 4   2 1   0
	+-----+------+-----+------+-----+-----+
	| VAL | rsvd | BAZ | rsvd | BAR | FOO |
	+-----+------+-----+------+-----+-----+

	BAZ bits mean:
		00 - nope
		01 - low
		10 - mid
		11 - high

we could describe it with:

"1fVAL|52r|2[nope,low,mid,high]BAZ|4r|3xBAR|2dFOO"

syntax is <width><fmt><name>

where width is the number of bits. Format is one of:

f - flag - print the name if the field is non-zero, else print nothing
    (or "-" to match the format you used above for CR4)
r - reserved - skip this field
d - print name=%d
x - print name=0x%x
[str0,str1,...str{2^width - 1}] - print NAME=str[val]

-Tony