From: Mike Rapoport <rppt@kernel.org>
To: Greg Thelen <gthelen@google.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>,
Pratyush Yadav <pratyush@kernel.org>,
Alexander Graf <graf@amazon.com>,
Andrew Morton <akpm@linux-foundation.org>,
Evangelos Petrongonas <epetron@amazon.de>,
kexec@lists.infradead.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] kho: check fdt_phys in is_kho_boot()
Date: Mon, 2 Nov 2026 10:36:09 +0200 [thread overview]
Message-ID: <auhLedAuD32WNcXW@kernel.org> (raw)
In-Reply-To: <20261023054518.3258350-1-gthelen@google.com>
Hi,
On Thu, Oct 22, 2026 at 10:45:18PM -0700, Greg Thelen wrote:
> During arm64 setup_arch(), efi_init() -> reserve_regions() calls
> is_kho_boot() before arm64_memblock_init() initializes memstart_addr.
> At this point memstart_addr still holds its initial sentinel value (-1).
>
> When booting via kexec with KHO enabled, kho_populate() sets
> kho_in.fdt_phys from the /chosen FDT node. Calling is_kho_boot() ->
> kho_get_fdt() invokes phys_to_virt(kho_in.fdt_phys), which evaluates
> PHYS_OFFSET and triggers VM_BUG_ON(memstart_addr & 1) on arm64 kernels
> built with CONFIG_DEBUG_VM=y:
Can't see the forest for the trees ;-)
Can you please translate the gist of the issue from LLMish to English?
> kernel BUG at ./arch/arm64/include/asm/memory.h:377!
> Internal error: Oops - BUG: 00000000f2000800 [#1] SMP
> Call trace:
> is_kho_boot+0x2c/0x38 (P)
> efi_init+0x94/0xf8
> setup_arch+0xf0/0x240
> start_kernel+0x84/0x490
> __primary_switched+0x88/0x98
>
> Check kho_in.fdt_phys directly in is_kho_boot() instead of calling
> kho_get_fdt() so that early boot callers do not invoke phys_to_virt()
> before the linear map offset is initialized.
>
> Fixes: d6d511639185 ("kexec: introduce is_kho_boot()")
> Assisted-by: Gemini:gemini-3.8-flash
> Signed-off-by: Greg Thelen <gthelen@google.com>
> ---
> kernel/liveupdate/kexec_handover.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
> index 7c4d86daf86d..d81baa38497f 100644
> --- a/kernel/liveupdate/kexec_handover.c
> +++ b/kernel/liveupdate/kexec_handover.c
> @@ -1630,7 +1630,7 @@ EXPORT_SYMBOL_GPL(kho_restore_free);
> */
> bool is_kho_boot(void)
> {
> - return !!kho_get_fdt();
> + return !!kho_in.fdt_phys;
> }
> EXPORT_SYMBOL_GPL(is_kho_boot);
>
> --
> 2.56.0.257.gf7497c7d27-goog
>
--
Sincerely yours,
Mike.
prev parent reply other threads:[~2026-11-02 8:36 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-23 5:45 [PATCH] kho: check fdt_phys in is_kho_boot() Greg Thelen
2026-10-23 16:37 ` Pratyush Yadav
2026-11-02 8:36 ` Mike Rapoport [this message]
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