* [PATCH] kho: check fdt_phys in is_kho_boot()
@ 2026-10-23 5:45 Greg Thelen
2026-10-23 5:49 ` sashiko-bot
2026-10-23 16:37 ` Pratyush Yadav
0 siblings, 2 replies; 3+ messages in thread
From: Greg Thelen @ 2026-10-23 5:45 UTC (permalink / raw)
To: Mike Rapoport, Pasha Tatashin, Pratyush Yadav, Alexander Graf
Cc: Andrew Morton, Evangelos Petrongonas, kexec, linux-mm,
linux-kernel, Greg Thelen
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:
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
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] kho: check fdt_phys in is_kho_boot()
2026-10-23 5:45 [PATCH] kho: check fdt_phys in is_kho_boot() Greg Thelen
@ 2026-10-23 5:49 ` sashiko-bot
2026-10-23 16:37 ` Pratyush Yadav
1 sibling, 0 replies; 3+ messages in thread
From: sashiko-bot @ 2026-10-23 5:49 UTC (permalink / raw)
To: Greg Thelen, Mike Rapoport, Pasha Tatashin, Pratyush Yadav,
Alexander Graf
Cc: Andrew Morton, Evangelos Petrongonas, kexec
> 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:
>
> 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>
Sashiko has reviewed this patch and found no issues.
--
Sashiko AI review · https://sashiko.dev/#/patchset/20261023054518.3258350-1-gthelen@google.com?part=1
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] kho: check fdt_phys in is_kho_boot()
2026-10-23 5:45 [PATCH] kho: check fdt_phys in is_kho_boot() Greg Thelen
2026-10-23 5:49 ` sashiko-bot
@ 2026-10-23 16:37 ` Pratyush Yadav
1 sibling, 0 replies; 3+ messages in thread
From: Pratyush Yadav @ 2026-10-23 16:37 UTC (permalink / raw)
To: Greg Thelen
Cc: Mike Rapoport, Pasha Tatashin, Pratyush Yadav, Alexander Graf,
Andrew Morton, Evangelos Petrongonas, kexec, linux-mm,
linux-kernel
On Thu, Oct 22 2026, 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:
>
> 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>
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
[...]
--
Regards,
Pratyush Yadav
^ permalink raw reply [flat|nested] 3+ messages in thread
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2026-10-23 5:45 [PATCH] kho: check fdt_phys in is_kho_boot() Greg Thelen
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2026-10-23 16:37 ` Pratyush Yadav
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