linux-kernel - Re: [PATCH] kdump, vmcoreinfo: Export sme_me

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Date:   Sat, 27 Oct 2018 00:25:17 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Petr Tesarik <ptesarik@...e.cz>
Cc:     lijiang <lijiang@...hat.com>, linux-kernel@...r.kernel.org,
        bhe@...hat.com, x86@...nel.org, kexec@...ts.infradead.org,
        mingo@...hat.com, tglx@...utronix.de, dyoung@...hat.com
Subject: Re: [PATCH] kdump, vmcoreinfo: Export sme_me_mask value to vmcoreinfo

On Fri, Oct 26, 2018 at 06:24:40PM +0200, Petr Tesarik wrote:
> But we need the MSR value from the panic kernel environment, not while
> the production kernel is still running, right?

Actually, we need only the encryption bit number (and it should be 0
otherwise to denote SME wasn't enabled).

I guess something like

	VMCOREINFO_NUMBER(sme_mask);

which gets written by the kexec-ed kernel.

> If so, then this reminds me that I have wanted for a long time to store
> more of the hardware state in a vmcore NOTE after a kernel crash ...
> control registers, MSRs and whatnot. Of course, this would be a
> long-term project, but I wonder what other people think about it in
> general.

I guess that sounds like a good idea - the more relevant hw info for
debugging, the better. Determining the important MSRs to save would need
a bit of a pondering over though. For example, some MSRs are per-core,
some per-socket, etc...

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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