linux-kernel - Re: [PATCH v2] x86/sev: Fix making shared pages private during kdump

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Message-ID: <20250430133159.GEaBImTw8E1cqU3k5C@fat_crate.local>
Date: Wed, 30 Apr 2025 15:31:59 +0200
From: Borislav Petkov <bp@...en8.de>
To: Ashish Kalra <Ashish.Kalra@....com>
Cc: tglx@...utronix.de, mingo@...hat.com, dave.hansen@...ux.intel.com,
	x86@...nel.org, thomas.lendacky@....com, hpa@...or.com,
	michael.roth@....com, nikunj@....com, seanjc@...gle.com,
	ardb@...nel.org, stable@...r.kernel.org,
	linux-kernel@...r.kernel.org, kexec@...ts.infradead.org,
	linux-coco@...ts.linux.dev
Subject: Re: [PATCH v2] x86/sev: Fix making shared pages private during kdump

On Mon, Apr 28, 2025 at 07:26:57PM +0000, Ashish Kalra wrote:
> There is a bug in this additional check for GHCB page contained

You don't write in the commit message that there is a bug - you explain what
the bug is.

> within a huge page which causes any shared page just below the
> per-cpu GHCB getting skipped from being transitioned back to private
> before kdump preparation which subsequently causes a 0x404 #VC
> exception when this shared page is accessed later while dumping guest
> memory during vmcore generation via kdump.

And you explain that *not* in a single, never-ending sentence but in simpler,
smaller, more palatable sentences. Imagine you're trying to explain this to
your colleagues who are not in your head.

I've been staring at the diff and trying to reverse-engineer what you're
trying to tell me in the commit message and I have an idea but I'm not sure.
And when I'm not sure, it often means the commit message needs more work.

So try again pls.

Thx.

-- 
Regards/Gruss,
    Boris.

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