Hi Geert,
On 1/11/22 17:04, Geert Uytterhoeven wrote:
Hi Palmer,
On Fri, Nov 19, 2021 at 5:47 PM Palmer Dabbelt palmer@rivosinc.com wrote:
From: Palmer Dabbelt palmer@rivosinc.com
For non-relocatable kernels we need to be able to link the kernel at approximately PAGE_OFFSET, thus requiring medany (as medlow requires the code to be linked within 2GiB of 0). The inverse doesn't apply, though: since medany code can be linked anywhere it's fine to link it close to 0, so we can support the smaller memory config.
Fixes: de5f4b8f634b ("RISC-V: Define MAXPHYSMEM_1GB only for RV32") Cc: stable@vger.kernel.org Signed-off-by: Palmer Dabbelt palmer@rivosinc.com
Thanks for your patch, which is now commit 9f36b96bc70f9707 ("RISC-V: MAXPHYSMEM_2GB doesn't depend on CMODEL_MEDLOW").
I found this when going through the savedefconfig diffs for the K210 defconfigs. I'm not entirely sure they're doing the right thing here (they should probably be setting CMODEL_LOW to take advantage of the better code generation), but I don't have any way to test those platforms so I don't want to change too much.
I can confirm MAXPHYSMEM_2GB works on K210 with CMODEL_MEDANY.
As the Icicle has 1760 MiB of RAM, I gave it a try with MAXPHYSMEM_2GB (and CMODEL_MEDANY), too. Unfortunately it crashes very early (needs earlycon to see):
OF: fdt: Ignoring memory range 0x80000000 - 0x80200000 Machine model: Microchip PolarFire-SoC Icicle Kit printk: debug: ignoring loglevel setting. earlycon: ns16550a0 at MMIO32 0x0000000020100000 (options '115200n8') printk: bootconsole [ns16550a0] enabled printk: debug: skip boot console de-registration. efi: UEFI not found. Unable to handle kernel paging request at virtual address ffffffff87e00001 Oops [#1] Modules linked in: CPU: 0 PID: 0 Comm: swapper Not tainted 5.16.0-08771-g85515233477d #56 Hardware name: Microchip PolarFire-SoC Icicle Kit (DT) epc : fdt_check_header+0x14/0x208 ra : early_init_dt_verify+0x16/0x94 epc : ffffffff802ddacc ra : ffffffff8082415a sp : ffffffff81203ee0 gp : ffffffff812ec3a8 tp : ffffffff8120cd80 t0 : 0000000000000005 t1 : 0000001040000000 t2 : ffffffff80000000 s0 : ffffffff81203f00 s1 : ffffffff87e00000 a0 : ffffffff87e00000 a1 : 000000040ffffce7 a2 : 00000000000000e7 a3 : ffffffff8080394c a4 : 0000000000000000 a5 : 0000000000000000 a6 : 0000000000000000 a7 : 0000000000000000 s2 : ffffffff81203f98 s3 : 8000000a00006800 s4 : fffffffffffffff3 s5 : 0000000000000000 s6 : 0000000000000001 s7 : 0000000000000000 s8 : 0000000020236c20 s9 : 0000000000000000 s10: 0000000000000000 s11: 0000000000000000 t3 : 0000000000000018 t4 : 00ff000000000000 t5 : 0000000000000000 t6 : 0000000000000010 status: 0000000200000100 badaddr: ffffffff87e00001 cause: 000000000000000d [<ffffffff802ddacc>] fdt_check_header+0x14/0x208 [<ffffffff8082415a>] early_init_dt_verify+0x16/0x94 [<ffffffff80802dee>] setup_arch+0xec/0x4ec [<ffffffff80800700>] start_kernel+0x88/0x6d6 random: get_random_bytes called fromprint_oops_end_marker+0x22/0x44 with crng_init=0 ---[ end trace 903df1a0ade0b876 ]--- Kernel panic - not syncing: Attempted to kill the idle task! ---[ end Kernel panic - not syncing: Attempted to kill the idle task! ]---
So the FDT is at 0xffffffff87e00000, i.e. at 0x7e00000 from the start of virtual memory (CONFIG_PAGE_OFFSET=0xffffffff80000000), and thus within the 2 GiB range.
I think you have just encountered what I suspected and mentioned in [1]: we recently moved the kernel to the PAGE_OFFSET address used with MAXPHYSMEM_2GB.
I would try to cherry-pick [1] and see if that works better :)
Alex
[1] https://patchwork.kernel.org/project/linux-riscv/patch/20211206104657.433304...
--- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -280,7 +280,7 @@ choice depends on 32BIT bool "1GiB" config MAXPHYSMEM_2GB
depends on 64BIT && CMODEL_MEDLOW
depends on 64BIT bool "2GiB" config MAXPHYSMEM_128GB depends on 64BIT && CMODEL_MEDANYGr{oetje,eeting}s,
Geert-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@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
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