From: Mike Rapoport <rppt@kernel.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Usama Arif <usamaarif642@gmail.com>,
Changyuan Lyu <changyuanl@google.com>,
akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
anthony.yznaga@oracle.com, arnd@arndb.de, ashish.kalra@amd.com,
benh@kernel.crashing.org, bp@alien8.de, catalin.marinas@arm.com,
corbet@lwn.net, dave.hansen@linux.intel.com,
devicetree@vger.kernel.org, dwmw2@infradead.org,
ebiederm@xmission.com, graf@amazon.com, jgowans@amazon.com,
kexec@lists.infradead.org, krzk@kernel.org,
linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org,
linux-mm@kvack.org, luto@kernel.org, mark.rutland@arm.com,
mingo@redhat.com, pasha.tatashin@soleen.com, pbonzini@redhat.com,
peterz@infradead.org, ptyadav@amazon.de, robh@kernel.org,
rostedt@goodmis.org, saravanak@google.com,
skinsburskii@linux.microsoft.com, tglx@linutronix.de,
thomas.lendacky@amd.com, will@kernel.org, x86@kernel.org,
Breno Leitao <leitao@debian.org>,
thevlad@meta.com
Subject: Re: [PATCH v8 12/17] x86/e820: temporarily enable KHO scratch for memory below 1M
Date: Tue, 25 Nov 2025 15:53:07 +0200 [thread overview]
Message-ID: <aSW0wySe2kRl1P8e@kernel.org> (raw)
In-Reply-To: <22BDBF5C-C831-4BBC-A854-20CA77234084@zytor.com>
On Mon, Nov 24, 2025 at 04:56:34PM -0800, H. Peter Anvin wrote:
> On November 24, 2025 11:24:58 AM PST, Usama Arif <usamaarif642@gmail.com> wrote:
>
> >diff --git a/arch/x86/realmode/init.c b/arch/x86/realmode/init.c
> >index 88be32026768c..1cd80293a3e23 100644
> >--- a/arch/x86/realmode/init.c
> >+++ b/arch/x86/realmode/init.c
> >@@ -66,8 +66,9 @@ void __init reserve_real_mode(void)
> > * setup_arch().
> > */
> > memblock_reserve(0, SZ_1M);
> >-
> >+#ifdef CONFIG_MEMBLOCK_KHO_SCRATCH
> > memblock_clear_kho_scratch(0, SZ_1M);
> >+#endif
> > }
> >
> > static void __init sme_sev_setup_real_mode(struct trampoline_header *th)
>
> What does "scratch" mean in this exact context? (Sorry, don't have the code in front of me.)
In this context it's the memory kexec handover used to bootstrap the
kexec'ed kernel. Everything beyond these scratch areas could contain
preserved data and kexec handover limits all early memory allocations to
these scratch areas.
--
Sincerely yours,
Mike.
next prev parent reply other threads:[~2025-11-25 13:53 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-05-09 7:46 [PATCH v8 00/17] kexec: introduce Kexec HandOver (KHO) Changyuan Lyu
2025-05-09 7:46 ` [PATCH v8 01/17] memblock: add MEMBLOCK_RSRV_KERN flag Changyuan Lyu
2025-10-10 9:33 ` Breno Leitao
2025-10-13 14:59 ` Pratyush Yadav
2025-10-13 16:40 ` Pratyush Yadav
2025-10-14 8:34 ` Breno Leitao
2025-10-14 13:10 ` Pratyush Yadav
2025-11-05 10:18 ` Breno Leitao
2025-11-06 8:24 ` Mike Rapoport
2025-05-09 7:46 ` [PATCH v8 02/17] memblock: Add support for scratch memory Changyuan Lyu
2025-05-09 7:46 ` [PATCH v8 03/17] memblock: introduce memmap_init_kho_scratch() Changyuan Lyu
2025-05-09 7:46 ` [PATCH v8 04/17] kexec: add Kexec HandOver (KHO) generation helpers Changyuan Lyu
2025-05-09 7:46 ` [PATCH v8 05/17] kexec: add KHO parsing support Changyuan Lyu
2025-05-09 7:46 ` [PATCH v8 06/17] kexec: enable KHO support for memory preservation Changyuan Lyu
2025-05-09 7:46 ` [PATCH v8 07/17] kexec: add KHO support to kexec file loads Changyuan Lyu
2025-05-09 7:46 ` [PATCH v8 08/17] kexec: add config option for KHO Changyuan Lyu
2025-05-09 7:46 ` [PATCH v8 09/17] arm64: add KHO support Changyuan Lyu
2025-05-09 7:46 ` [PATCH v8 10/17] x86/setup: use memblock_reserve_kern for memory used by kernel Changyuan Lyu
2025-05-09 7:46 ` [PATCH v8 11/17] x86/kexec: add support for passing kexec handover (KHO) data Changyuan Lyu
2025-05-09 7:46 ` [PATCH v8 12/17] x86/e820: temporarily enable KHO scratch for memory below 1M Changyuan Lyu
2025-11-24 19:24 ` Usama Arif
2025-11-25 0:56 ` H. Peter Anvin
2025-11-25 12:23 ` Pratyush Yadav
2025-11-25 13:53 ` Mike Rapoport [this message]
2025-11-25 13:15 ` Pratyush Yadav
2025-11-25 13:50 ` Mike Rapoport
2025-11-25 18:47 ` Usama Arif
2025-11-26 6:14 ` Mike Rapoport
2025-11-26 7:25 ` Usama Arif
2025-11-25 14:31 ` Usama Arif
2025-11-25 14:39 ` Pratyush Yadav
2025-05-09 7:46 ` [PATCH v8 13/17] x86/boot: make sure KASLR does not step over KHO preserved memory Changyuan Lyu
2025-05-09 7:46 ` [PATCH v8 14/17] x86/Kconfig: enable kexec handover for 64 bits Changyuan Lyu
2025-05-09 7:46 ` [PATCH v8 15/17] memblock: add KHO support for reserve_mem Changyuan Lyu
2025-05-09 7:46 ` [PATCH v8 16/17] Documentation: add documentation for KHO Changyuan Lyu
2025-05-09 7:46 ` [PATCH v8 17/17] Documentation: KHO: Add memblock bindings Changyuan Lyu
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