From: Will Deacon <will@kernel.org>
To: Catalin Marinas <catalin.marinas@arm.com>,
Ard Biesheuvel <ardb@kernel.org>,
Breno Leitao <leitao@debian.org>
Cc: kernel-team@android.com, Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, kernel-team@meta.com
Subject: Re: [PATCH] arm64: trans_pgd: clone only the linear map that exists at runtime
Date: Thu, 3 Sep 2026 14:59:18 +0100 [thread overview]
Message-ID: <178844047586.4162266.2394578462363547662.b4-ty@kernel.org> (raw)
In-Reply-To: <20260828-b4-arm64-trans-pgd-va52-v1-1-a66644372673@debian.org>
On Fri, 28 Aug 2026 02:28:18 -0700, Breno Leitao wrote:
> kexec_file_load() fails on arm64 if we have CONFIG_ARM64_VA_BITS_52 but
> it runs on a !FEAT_LPA2 host (such as my loving Grace machine).
>
> That is because trans_pgd_create_copy() uses the compile time
> PAGE_OFFSET (VA 52) instead of the actual VA size (48 -- due to the lack
> of LPA2). With the fifth level folded, pgd_none() is always false, so
> the walk cannot skip the 15 extra PGDIR_SIZE slots, and they all alias
> back to the same table: the whole kernel page table gets cloned 16
> times, KASAN shadow included. Without KASAN it does not blow up, it just
> wastes ~RAM/32 in page tables.
>
> [...]
Applied to arm64 (for-next/fixes), thanks!
[1/1] arm64: trans_pgd: clone only the linear map that exists at runtime
https://git.kernel.org/arm64/c/1537e55728ec
Cheers,
--
Will
https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev
prev parent reply other threads:[~2026-09-03 13:59 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-28 9:28 [PATCH] arm64: trans_pgd: clone only the linear map that exists at runtime Breno Leitao
2026-09-02 13:16 ` Yury MonZon
2026-09-03 13:59 ` Will Deacon [this message]
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