linux-kernel - Re: [PATCH v7 12/18] x86/kexec: add support for passing kexec handover (KHO) data

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Message-ID: <9dcf8bd9-f4c3-4c7d-a717-ff3eb95f12b9@intel.com>
Date: Fri, 2 May 2025 11:39:02 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: Changyuan Lyu <changyuanl@...gle.com>, linux-kernel@...r.kernel.org
Cc: akpm@...ux-foundation.org, anthony.yznaga@...cle.com, arnd@...db.de,
 ashish.kalra@....com, benh@...nel.crashing.org, bp@...en8.de,
 catalin.marinas@....com, corbet@....net, dave.hansen@...ux.intel.com,
 devicetree@...r.kernel.org, dwmw2@...radead.org, ebiederm@...ssion.com,
 graf@...zon.com, hpa@...or.com, jgowans@...zon.com,
 kexec@...ts.infradead.org, krzk@...nel.org,
 linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
 linux-mm@...ck.org, luto@...nel.org, mark.rutland@....com, mingo@...hat.com,
 pasha.tatashin@...een.com, pbonzini@...hat.com, peterz@...radead.org,
 ptyadav@...zon.de, robh@...nel.org, rostedt@...dmis.org, rppt@...nel.org,
 saravanak@...gle.com, skinsburskii@...ux.microsoft.com, tglx@...utronix.de,
 thomas.lendacky@....com, will@...nel.org, x86@...nel.org
Subject: Re: [PATCH v7 12/18] x86/kexec: add support for passing kexec
 handover (KHO) data

On 5/1/25 15:54, Changyuan Lyu wrote:
> From: Alexander Graf <graf@...zon.com>
> 
> kexec handover (KHO) creates a metadata that the kernels pass between each
> other during kexec. This metadata is stored in memory and kexec image
> contains a (physical) pointer to that memory.
> 
> In addition, KHO keeps "scratch regions" available for kexec: physically
> contiguous memory regions that are guaranteed to not have any memory that
> KHO would preserve. The new kernel bootstraps itself using the scratch
> regions and sets all handed over memory as in use. When subsystems that
> support KHO initialize, they introspect the KHO metadata, restore preserved
> memory regions, and retrieve their state stored in the preserved memory.
> 
> Enlighten x86 kexec-file and boot path about the KHO metadata and make sure
> it gets passed along to the next kernel.

Acked-by: Dave Hansen <dave.hansen@...ux.intel.com>