[PATCH v2] kho: skip KHO for crash kernel

[PATCH v2] kho: skip KHO for crash kernel

[Evangelos Petrongonas]

kho_fill_kimage() unconditionally populates the kimage with KHO
metadata for every kexec image type. When the image is a crash kernel,
this can be problematic as the crash kernel can run in a small reserved
region and the KHO scratch areas can sit outside it.
The crash kernel then faults during kho_memory_init() when it
tries phys_to_virt() on the KHO FDT address:

  Unable to handle kernel paging request at virtual address xxxxxxxx
  ...
    fdt_offset_ptr+...
    fdt_check_node_offset_+...
    fdt_first_property_offset+...
    fdt_get_property_namelen_+...
    fdt_getprop+...
    kho_memory_init+...
    mm_core_init+...
    start_kernel+...

kho_locate_mem_hole() already skips KHO logic for KEXEC_TYPE_CRASH
images, but kho_fill_kimage() was missing the same guard. As
kho_fill_kimage() is the single point that populates image->kho.fdt
and image->kho.scratch, fixing it here is sufficient for both arm64
and x86 as the FDT and boot_params path are bailing out when these
fields are unset.

Fixes: d7255959b69a ("kho: allow kexec load before KHO finalization")
Signed-off-by: Evangelos Petrongonas <epetron@amazon.de>
---

v2: Per Mike's review [1], move the guard into kho_fill_kimage() instead
    of patching the arch-level producers and consumers. This fixes
    both arm64 and x86 in one place and avoids redundant checks. Tested again.

Note regarding backporting
The offending commit was deployed with 6.19. The only other supported
kernel version with 6.18, unless I miss someting uses
```
if (!kho_out.finalized)
```
which in the case of crash kernel it shouldn't be finalised.


[1] https://lore.kernel.org/all/ade2ExpM8ROXV-vy@kernel.org/

 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 cc68a3692905..1029fe8778f2 100644
--- a/kernel/liveupdate/kexec_handover.c
+++ b/kernel/liveupdate/kexec_handover.c
@@ -1551,7 +1551,7 @@ int kho_fill_kimage(struct kimage *image)
 	int err = 0;
 	struct kexec_buf scratch;
 
-	if (!kho_enable)
+	if (!kho_enable || image->type == KEXEC_TYPE_CRASH)
 		return 0;
 
 	image->kho.fdt = virt_to_phys(kho_out.fdt);
-- 
2.47.3




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