Hi Marek,
On Tue, 3 Nov 2026 at 20:25, Marek Szyprowski <m.szyprowski at samsung.com> wrote:
> On 03.11.2026 19:04, Geert Uytterhoeven wrote:
> > On Thu, 15 Oct 2026 at 10:29, Marek Szyprowski <m.szyprowski at samsung.com> wrote:
> >> Get rid of the static, limited-size reserved_mem array and replace it
> >> with array allocated by memblock_alloc_raw() and accessed directly or
> >> through a temporary early_memremap() mapping (depending on the
> >> architecture support). Such mapping is needed for some architectures
> >> (like ARM64), where linear map is not yet available during early boot
> >> scan. The array is allocated from the bottom of RAM to avoid placing it
> >> in highmem area, because some architectures (e.g. Xtensa, C-SKY, MIPS32)
> >> set the memblock limit to the end of lowmem only after the early scan.
> >> The early mapping is not used on PPC64, where the scan is done before
> >> early_ioremap_setup(), but the memory allocated by memblock is already
> >> accessible at that point.
> >>
> >> Having a single, writeable array with all reserved regions removes the
> >> need to perform two step initialization introduced by commit
> >> 8a6e02d0c00e ("of: reserved_mem: Restructure how the reserved memory
> >> regions are processed"), so all regions can be processed during the
> >> early scan again.
> >>
> >> The reserved_mem array is allocated only after all static (defined by
> >> the 'reg' property) regions are marked as reserved or no-map, so it
> >> cannot be placed in any of them. Errors of the early reservations are
> >> not recorded per region, only the fact that some of them failed is
> >> stored and a message asking to fix the device-tree is printed. The
> >> region specific init functions for the static regions are then called
> >> in a separate pass, once the array is available. Then all dynamically
> >> allocated reserved regions are processed.
> >>
> >> Suggested-by: Mike Rapoport <rppt at kernel.org>
> >> Link: https://lore.kernel.org/all/asc6brs_g0ky0wOM@kernel.org/
> >> Signed-off-by: Marek Szyprowski <m.szyprowski at samsung.com>
> > Thanks for your patch, which is now commit aa05faf815836c47 ("of:
> > reserved_mem: allocate and map the reserved_mem array early")
> > in dt-rh/for-next.
> >
> > This causes an early crash on BeagleV Starlight Beta:
> >
> > [...]
> > earlycon: uart0 MMIO32:0x0000000012440000 (options '115200n8')
> > printk: legacy bootconsole [uart0] enabled
> > printk: debug: skip boot console de-registration.
> > efi: UEFI not found.
> > -OF: reserved mem: 0x00000000fb000000..0x00000000fcffffff (32768 KiB)
> > map non-reusable framebuffer at fb000000
> > -OF: reserved mem: 0x00000000f9000000..0x00000000f9ffffff (16384 KiB)
> > map non-reusable framebuffer at f9000000
> > -OF: reserved mem: 0x00000000d0000000..0x00000000f7ffffff (655360 KiB)
> > map non-reusable framebuffer at d0000000
> > -OF: reserved mem: 0x00000000c9000000..0x00000000ccffffff (65536 KiB)
> > map non-reusable framebuffer at c9000000
> > -OF: reserved mem: 0x00000000fa000000..0x00000000faffffff (16384 KiB)
> > nomap non-reusable dma-reserved at fa000000
> > -Reserved memory: created DMA memory pool at 0x000000107a000000, size 16384 KiB
> > -OF: reserved mem: initialized node linux,dma at 107a000000, compatible
> > id shared-dma-pool
> > -OF: reserved mem: 0x000000107a000000..0x000000107affffff (16384 KiB)
> > nomap non-reusable linux,dma at 107a000000
> > -SBI HSM extension detected
> > -[...]
> > +Oops - store (or AMO) access fault [#1]
> > +Modules linked in:
> > +CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted
> > 7.4.0-rc1-starlight-00002-gaa05faf81583 #411 PREEMPT
> > +Hardware name: BeagleV Starlight Beta (DT)
> > +epc : __memset+0x68/0xfe
> > + ra : fdt_scan_reserved_mem+0x3a4/0x80a
> > +epc : ffffffff8087fd88 ra : ffffffff80a313c8 sp : ffffffff81403c20
> > + gp : ffffffff814dc6c0 tp : ffffffff8140cf80 t0 : ffffffc4fea38ff0
> > + t1 : 0000000080200000 t2 : ffffffc4fec03008 s0 : ffffffff81403d10
> > + s1 : ffffffffffffffff a0 : ffffffc4fea39000 a1 : 0000000000000000
> > + a2 : 00000000000000f0 a3 : ffffffc4fea390f0 a4 : 0000000000000008
> > + a5 : ffffffff8087fd88 a6 : 00000000000000f0 a7 : 0000000000001000
> > + s2 : ffffffc4fec00000 s3 : 00000000000000f0 s4 : 0000000000000000
> > + s5 : 0000000000002de0 s6 : 0000000000000006 s7 : fffffffffefefefe
> > + s8 : ffffffc4fec02fd4 s9 : ffffffff8148e318 s10: fffffffffefefeff
> > + s11: ffffffc4fea39000 t3 : ffffffff8150df00 t4 : ffffffff8150df00
> > + t5 : ffffffff8150df00 t6 : ffffffff8150df78 ssp : 0000000000000000
> > +status: 0000000200000100 badaddr: ffffffc4fea39000 cause: 0000000000000007
> > +[<ffffffff8087fd88>] __memset+0x68/0xfe
> > +[<ffffffff80a2f63a>] early_init_fdt_scan_reserved_mem+0xa4/0x110
> > +[<ffffffff80a06c8e>] paging_init+0x17c/0x46a
> > +[<ffffffff80a046dc>] setup_arch+0xdc/0x584
> > +[<ffffffff80a009b8>] start_kernel+0x98/0x940
> > +Code: 0000 8793 00e7 8305 97ba 8782 b023 00b2 b423 00b2 (b823) 00b2
> > +---[ end trace 0000000000000000 ]---
> > +Kernel panic - not syncing: Fatal exception in interrupt
> > +---[ end Kernel panic - not syncing: Fatal exception in interrupt ]---
> >
> > Reverting the commit fixes the issue.
>
> Does moving early_init_fdt_scan_reserved_mem() to the end of setup_bootmem()
> in arch/riscv/mm/init.c change anything?
Unfortunately that doesn't make a difference.
> Could You provide a full boot log from the working kernel and /proc/iomem dump?
Sent by personal email.
The relevant part of /proc/iomem is:
80000000-cfffffff : System RAM
80200000-80201fff : Reserved
80202000-81730bf7 : Kernel image
80202000-80aa7e73 : Kernel code
81000000-813fffff : Kernel rodata
81600000-816dd9ff : Kernel data
816de000-81730bf7 : Kernel bss
81730bf8-817fffff : Reserved
88000000-88007fff : Reserved
9c000000-c7ffffff : Reserved
c9000000-ccffffff : Reserved
d0000000-f7ffffff : Reserved
f8000000-f8ffffff : System RAM
f9000000-fcffffff : Reserved
fd000000-27fffffff : System RAM
2772e1000-2773a0fff : Reserved
2773a1000-277fa1fff : Reserved
277fa2000-277fcbfff : Reserved
277fce000-277fcefff : Reserved
277fcf000-27ffcffff : Reserved
27ffd0000-27fff6fff : Reserved
27fff7000-27fffffff : Reserved
Thanks!
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds