arm64: Kexec: Warning: virt_to_phys used for non-linear address

[Breno Leitao <leitao@debian.org>]

Hello,

I am setting the following warning when loading a kdump kernel in
ACPI-based aarch64 box, running upstream and linux-next (stack below
against 5f703ce5c981).

  virt_to_phys used for non-linear address: 00000000cf9a4e41 (0xffffffffff5e0000)
  WARNING: CPU: 35 PID: 2279 at arch/arm64/mm/physaddr.c:15 __virt_to_phys (arch/arm64/mm/physaddr.c:17)
  Modules linked in: sunrpc(E) ipmi_ssif(E) nvidia_cspmu(E) arm_cspmu_module(E) arm_smmuv3_pmu(E) coresight_trbe(E) mlx5_ib(E) ib_uverbs(E) ipmi_devintf(E) ipmi_msghandler(E) coresight_stm(E) coresight_tmc(E) coresight_funnel(E) stm_core(E) coresight_etm4x(E) coresight(E) cppc_cpufreq(E) sch_fq_codel(E) drm(E) backlight(E) drm_panel_orientation_quirks(E) crct10dif_ce(E) sm3_ce(E) sm3(E) sha3_ce(E) sha512_ce(E) sha512_arm64(E) xhci_pci(E) xhci_hcd(E) spi_tegra210_quad(E) nbd(E) acpi_power_meter(E) loop(E) efivarfs(E) autofs4(E)
  Hardware name: Quanta Java Island EVT 29F0EMAZ046/Java Island, BIOS F0EJ3A01 06/03/2024
  pstate: 63400009 (nZCv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
  pc : __virt_to_phys (arch/arm64/mm/physaddr.c:17)
  lr : __virt_to_phys (arch/arm64/mm/physaddr.c:17)
  sp : ffff8000be1cf9f0
  x29: ffff8000be1cf9f0 x28: dfff800000000000 x27: ffff800083ca9630
  x26: ffff800083ca9000 x25: 1ffff000107952c6 x24: ffff0000ff1b6800
  x23: 0000000000000000 x22: 0000000000001687 x21: ffff0001ecd46800
  x20: ffff000103524000 x19: ffffffffff5e0000 x18: ffffffffffffffff
  x17: ffff8000802d07d4 x16: 2930303030653566 x15: 0000000000000001
  x14: 1ffff00017c39ed8 x13: 0000000000000000 x12: 0000000000000000
  x11: ffff700017c39ed9 x10: 0000000000000002 x9 : e7a4565c7b34a200
  x8 : ffff800083c50000 x7 : 0000000000000001 x6 : 0000000000000001
  x5 : ffff8000be1cf6a0 x4 : ffff800084a5ff40 x3 : ffff800081580960
  x2 : 0000000000000001 x1 : ffff800083253340 x0 : 000000000000004f
  Call trace:
  __virt_to_phys (arch/arm64/mm/physaddr.c:17)
  of_kexec_alloc_and_setup_fdt (drivers/of/kexec.c:305)
  load_other_segments (arch/arm64/kernel/machine_kexec_file.c:162)
  image_load (arch/arm64/kernel/kexec_image.c:103)
  __arm64_sys_kexec_file_load (kernel/kexec_file.c:73 kernel/kexec_file.c:257 kernel/kexec_file.c:296 kernel/kexec_file.c:374 kernel/kexec_file.c:332 kernel/kexec_file.c:332)
  invoke_syscall (arch/arm64/kernel/syscall.c:? arch/arm64/kernel/syscall.c:48)
  el0_svc_common (./include/linux/thread_info.h:127 arch/arm64/kernel/syscall.c:141)
  do_el0_svc (arch/arm64/kernel/syscall.c:153)
  el0_svc (arch/arm64/kernel/entry-common.c:165 arch/arm64/kernel/entry-common.c:178 arch/arm64/kernel/entry-common.c:713)
  el0t_64_sync_handler (arch/arm64/kernel/entry-common.c:781)
  el0t_64_sync (arch/arm64/kernel/entry.S:598)
  irq event stamp: 49964
  hardirqs last enabled at (49963): console_unlock (kernel/printk/printk.c:? kernel/printk/printk.c:2746 kernel/printk/printk.c:3065)
  hardirqs last disabled at (49964): el1_dbg (arch/arm64/kernel/entry-common.c:371 arch/arm64/kernel/entry-common.c:471)
  softirqs last enabled at (49942): handle_softirqs (./arch/arm64/include/asm/preempt.h:13 kernel/softirq.c:401 kernel/softirq.c:582)
  softirqs last disabled at (49937): __do_softirq (kernel/softirq.c:589)
  ---[ end trace 0000000000000000 ]---


This is happening on the following code:

        /* Remove memory reservation for the current device tree. */
        ret = fdt_find_and_del_mem_rsv(fdt, __pa(initial_boot_params),
                                       fdt_totalsize(initial_boot_params));


Where `initial_boot_params` contains a copy of the fdt allocated at init
time, and as I've analyzed, it is a virtual address and can be
translated by the MMU.

Since __pa() is a macro to __virt_to_phys():

	#define __pa(x)                 __virt_to_phys((unsigned long)(x))

I am curious why this address is special that makes __virt_to_phys()
unhappy.

Have you seen this before? Any tip on how to debug this further?

Thanks