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Date:   Tue, 25 Oct 2022 12:25:36 +0200
From:   Borislav Petkov <bp@alien8.de>
To:     "Kalra, Ashish" <ashish.kalra@amd.com>, vbabka@suse.cz
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Subject: Re: [PATCH Part2 v6 14/49] crypto: ccp: Handle the legacy TMR
 allocation when SNP is enabled
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References: <cover.1655761627.git.ashish.kalra@amd.com>
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On Fri, Oct 14, 2022 at 03:00:09PM -0500, Kalra, Ashish wrote:
> If it is "still" accessed/touched then it can cause RMP #PF.
> On the other hand,
> 
>  * PG_hwpoison... Accessing is
>  * not safe since it may cause another machine check. Don't touch!
> 
> That sounds exactly the state we want these page(s) to be in ?
> 
> Another possibility is PG_error.

Something like this:

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index e66f7aa3191d..baffa9c0dc30 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -186,6 +186,7 @@ enum pageflags {
 	 * THP.
 	 */
 	PG_has_hwpoisoned = PG_error,
+	PG_offlimits = PG_hwpoison,
 #endif
 
 	/* non-lru isolated movable page */

and SNP will have to depend on CONFIG_MEMORY_FAILURE.

But I'd let mm folks correct me here on the details.

-- 
Regards/Gruss,
    Boris.

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