From: "Ard Biesheuvel" <ardb@kernel.org>
To: "Ard Biesheuvel" <ardb+git@google.com>, linux-kernel@vger.kernel.org
Cc: linux-efi@vger.kernel.org, x86@kernel.org,
"Mike Rapoport" <rppt@kernel.org>,
"Benjamin Herrenschmidt" <benh@kernel.crashing.org>
Subject: Re: [PATCH v2 00/19] efi/x86: Avoid the need to mangle the EFI memory map
Date: Tue, 24 Mar 2026 10:50:05 +0100 [thread overview]
Message-ID: <f4c11afa-e934-4457-8a3b-89a0ad2f4263@app.fastmail.com> (raw)
In-Reply-To: <20260319090529.1091660-21-ardb+git@google.com>
On Thu, 19 Mar 2026, at 10:05, Ard Biesheuvel wrote:
> From: Ard Biesheuvel <ardb@kernel.org>
>
> At boot, x86 uses E820 tables, memblock tables and the EFI memory map to
> reason about which parts of system RAM are available to the OS, and
> which are reserved.
>
> While other EFI architectures treat the EFI memory map as immutable, the
> x86 boot code modifies it to keep track of memory reservations of boot
> services data regions, in order to distinguish which parts have been
> memblock_reserve()'d permanently, and which ones have been reserved only
> temporarily to work around buggy implementations of the EFI runtime
> service [SetVirtualAddressMap()] that reconfigures the VA space of the
> runtime services themselves.
>
> This method is mostly fine for marking entire regions as reserved, but
> it gets complicated when the code decides to split EFI memory map
> entries in order to mark some of it permanently reserved, and the rest
> of it temporarily reserved.
>
> Let's clean this up, by
> - marking permanent reservations of EFI boot services data memory as
> MEMBLOCK_RSRV_KERN
> - taking this marking into account when deciding whether or not a EFI
> boot services data region can be freed
> - dropping all of the EFI memory map insertion/splitting logic and the
> allocation/freeing logic, all of which have become redundant.
>
Please disregard this for now. Sashiko pointed out some fundamental issues in this series, and I think it might be better to take a different approach entirely.
prev parent reply other threads:[~2026-03-24 9:50 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-19 9:05 [PATCH v2 00/19] efi/x86: Avoid the need to mangle the EFI memory map Ard Biesheuvel
2026-03-19 9:05 ` [PATCH v2 01/19] memblock: Permit existing reserved regions to be marked RSRV_KERN Ard Biesheuvel
2026-03-19 9:05 ` [PATCH v2 02/19] efi: Tag memblock reservations of boot services regions as RSRV_KERN Ard Biesheuvel
2026-03-19 9:05 ` [PATCH v2 03/19] x86/efi: Unmap kernel-reserved boot regions from EFI page tables Ard Biesheuvel
2026-03-19 9:05 ` [PATCH v2 04/19] x86/efi: Drop EFI_MEMORY_RUNTIME check from __ioremap_check_other() Ard Biesheuvel
2026-03-19 9:05 ` [PATCH v2 05/19] x86/efi: Omit RSRV_KERN memblock reservations when freeing boot regions Ard Biesheuvel
2026-03-19 9:05 ` [PATCH v2 06/19] x86/efi: Defer sub-1M check from unmap to free stage Ard Biesheuvel
2026-03-19 9:05 ` [PATCH v2 07/19] x86/efi: Simplify real mode trampoline allocation quirk Ard Biesheuvel
2026-03-19 9:05 ` [PATCH v2 08/19] x86/efi: Omit redundant kernel image overlap check Ard Biesheuvel
2026-03-19 9:05 ` [PATCH v2 09/19] x86/efi: Drop redundant EFI_PARAVIRT check Ard Biesheuvel
2026-03-19 9:05 ` [PATCH v2 10/19] x86/efi: Do not rely on EFI_MEMORY_RUNTIME bit and avoid entry splitting Ard Biesheuvel
2026-03-19 9:05 ` [PATCH v2 11/19] efi: Use nr_map not map_end to find the last valid memory map entry Ard Biesheuvel
2026-03-19 9:05 ` [PATCH v2 12/19] x86/efi: Only merge EFI memory map entries on 32-bit systems Ard Biesheuvel
2026-03-19 9:05 ` [PATCH v2 13/19] x86/efi: Clean the memory map using iterator and filter API Ard Biesheuvel
2026-03-19 9:05 ` [PATCH v2 14/19] x86/efi: Update the runtime map in place Ard Biesheuvel
2026-03-19 9:05 ` [PATCH v2 15/19] x86/efi: Use iterator API when mapping EFI regions for runtime Ard Biesheuvel
2026-03-19 9:05 ` [PATCH v2 16/19] x86/efi: Reuse memory map instead of reallocating it Ard Biesheuvel
2026-03-19 9:05 ` [PATCH v2 17/19] x86/efi: Defer compaction of the EFI memory map Ard Biesheuvel
2026-03-19 9:05 ` [PATCH v2 18/19] x86/efi: Do not abuse RUNTIME bit to mark boot regions as reserved Ard Biesheuvel
2026-03-19 9:05 ` [PATCH v2 19/19] x86/efi: Free unused tail of the EFI memory map Ard Biesheuvel
2026-03-24 9:50 ` Ard Biesheuvel [this message]
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