Messages in this thread | | | Date | Thu, 9 Mar 2023 13:31:24 +0100 | Subject | Re: RISC-V reserved memory problems | From | Alexandre Ghiti <> |
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On 3/9/23 11:30, Alexandre Ghiti wrote: > Hi Conor, > > On 8/16/22 22:41, Conor.Dooley@microchip.com wrote: >> Hey all, >> We've run into a bit of a problem with reserved memory on PolarFire, or >> more accurately a pair of problems that seem to have opposite fixes. >> >> The first of these problems is triggered when trying to implement a >> remoteproc driver. To get the reserved memory buffer, remoteproc >> does an of_reserved_mem_lookup(), something like: >> >> np = of_parse_phandle(pdev->of_node, "memory-region", 0); >> if (!np) >> return -EINVAL; >> >> rmem = of_reserved_mem_lookup(np); >> if (!rmem) >> return -EINVAL; >> >> of_reserved_mem_lookup() then uses reserved_mem[i].name to try and find >> a match - but this was triggering kernel panics for us. We did some >> debugging and found that the name string's pointer was pointing to an >> address in the 0x4000_0000 range. The minimum reproduction for this > > > 0x4000_0000 corresponds to DTB_EARLY_BASE_VA: this is the address that > is used to map the dtb before we can access it using the linear mapping. > > >> crash is attached - it hacks in some print_reserved_mem()s into >> setup_vm_final() around a tlb flush so you can see the before/after. >> (You'll need a reserved memory node in your dts to replicate) >> >> The output is like so, with the same crash as in the remoteproc driver: >> >> [ 0.000000] Linux version 6.0.0-rc1-00001-g0d9d6953d834 >> (conor@wendy) (riscv64-unknown-linux-gnu-gcc (g5964b5cd727) 11.1.0, >> GNU ld (GNU Binutils) 2.37) #1 SMP Tue Aug 16 13:42:09 IST 2022 >> [ 0.000000] OF: fdt: Ignoring memory range 0x80000000 - 0x80200000 >> [ 0.000000] Machine model: Microchip PolarFire-SoC Icicle Kit >> [ 0.000000] earlycon: ns16550a0 at MMIO32 0x0000000020100000 >> (options '115200n8') >> [ 0.000000] printk: bootconsole [ns16550a0] enabled >> [ 0.000000] printk: debug: skip boot console de-registration. >> [ 0.000000] efi: UEFI not found. >> [ 0.000000] before flush >> [ 0.000000] OF: reserved mem: debug name is fabricbuf@ae000000 >> [ 0.000000] after flush >> [ 0.000000] Unable to handle kernel paging request at virtual >> address 00000000401c31ac > > > You take the trap here because the mapping for the dtb does not exist > in swapper_pg_dir, but you don't need this mapping anymore as you can > access the device tree through the linear mapping now.
You can forget everything below, I was completely wrong. I'll follow up on Mike's answer.
> > I would say that: you build your kernel with CONFIG_BUILTIN_DTB and > then you don't call early_init_dt_verify which resets > initial_boot_params to the linear mapping address (it was initially > set to 0x4000_0000 in parse_dtb). If that's the case, does the > following fix your issue? > > > diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c > index 376d2827e736..2b09f0bd8432 100644 > --- a/arch/riscv/kernel/setup.c > +++ b/arch/riscv/kernel/setup.c > @@ -276,6 +276,7 @@ void __init setup_arch(char **cmdline_p) > efi_init(); > paging_init(); > #if IS_ENABLED(CONFIG_BUILTIN_DTB) > + initial_boot_params = __va(XIP_FIXUP(dtb_early_pa)); > unflatten_and_copy_device_tree(); > #else > if (early_init_dt_verify(__va(XIP_FIXUP(dtb_early_pa)))) > > >> [ 0.000000] Oops [#1] >> [ 0.000000] Modules linked in: >> [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted >> 6.0.0-rc1-00001-g0d9d6953d834 #1 >> [ 0.000000] Hardware name: Microchip PolarFire-SoC Icicle Kit (DT) >> [ 0.000000] epc : string+0x4a/0xea >> [ 0.000000] ra : vsnprintf+0x1e4/0x336 >> [ 0.000000] epc : ffffffff80335ea0 ra : ffffffff80338936 sp : >> ffffffff81203be0 >> [ 0.000000] gp : ffffffff812e0a98 tp : ffffffff8120de40 t0 : >> 0000000000000000 >> [ 0.000000] t1 : ffffffff81203e28 t2 : 7265736572203a46 s0 : >> ffffffff81203c20 >> [ 0.000000] s1 : ffffffff81203e28 a0 : ffffffff81203d22 a1 : >> 0000000000000000 >> [ 0.000000] a2 : ffffffff81203d08 a3 : 0000000081203d21 a4 : >> ffffffffffffffff >> [ 0.000000] a5 : 00000000401c31ac a6 : ffff0a00ffffff04 a7 : >> ffffffffffffffff >> [ 0.000000] s2 : ffffffff81203d08 s3 : ffffffff81203d00 s4 : >> 0000000000000008 >> [ 0.000000] s5 : ffffffff000000ff s6 : 0000000000ffffff s7 : >> 00000000ffffff00 >> [ 0.000000] s8 : ffffffff80d9821a s9 : ffffffff81203d22 s10: >> 0000000000000002 >> [ 0.000000] s11: ffffffff80d9821c t3 : ffffffff812f3617 t4 : >> ffffffff812f3617 >> [ 0.000000] t5 : ffffffff812f3618 t6 : ffffffff81203d08 >> [ 0.000000] status: 0000000200000100 badaddr: 00000000401c31ac >> cause: 000000000000000d >> [ 0.000000] [<ffffffff80338936>] vsnprintf+0x1e4/0x336 >> [ 0.000000] [<ffffffff80055ae2>] vprintk_store+0xf6/0x344 >> [ 0.000000] [<ffffffff80055d86>] vprintk_emit+0x56/0x192 >> [ 0.000000] [<ffffffff80055ed8>] vprintk_default+0x16/0x1e >> [ 0.000000] [<ffffffff800563d2>] vprintk+0x72/0x80 >> [ 0.000000] [<ffffffff806813b2>] _printk+0x36/0x50 >> [ 0.000000] [<ffffffff8068af48>] print_reserved_mem+0x1c/0x24 >> [ 0.000000] [<ffffffff808057ec>] paging_init+0x528/0x5bc >> [ 0.000000] [<ffffffff808031ae>] setup_arch+0xd0/0x592 >> [ 0.000000] [<ffffffff8080070e>] start_kernel+0x82/0x73c >> [ 0.000000] ---[ end trace 0000000000000000 ]--- >> [ 0.000000] Kernel panic - not syncing: Attempted to kill the idle >> task! >> [ 0.000000] ---[ end Kernel panic - not syncing: Attempted to kill >> the idle task! ]--- >> >> We traced this back to early_init_fdt_scan_reserved_mem() in >> setup_bootmem() - moving it later back up the boot sequence to >> after the dt has been remapped etc has fixed the problem for us. >> >> The least movement to get it working is attached, and also pushed >> here: git.kernel.org/conor/c/1735589baefc >> >> The second problem is a bit more complicated to explain - but we >> found the solution conflicted with the remoteproc fix as we had >> to move early_init_fdt_scan_reserved_mem() _earlier_ in the boot >> process to solve this one. >> >> We want to have a node in our devicetree that contains some memory >> that is non-cached & marked as reserved-memory. Maybe we have just >> missed something, but from what we've seen: >> - the really early setup looks at the dtb, picks the highest bit >> of memory and puts the dtb etc there so it can start using it >> - early_init_fdt_scan_reserved_mem() is then called, which figures >> out if memory is reserved or not. >> >> Unfortunately, the highest bit of memory is the non-cached bit so >> everything falls over, but we can avoid this by moving the call to >> early_init_fdt_scan_reserved_mem() above the dtb memblock alloc that >> takes place right before it in setup_bootmem(). > > > And then I suppose the allocations you are mentioning happen in > unflatten_XXX, so parsing the device tree for reserved memory nodes > before this should do the trick. Does the following fix your second > issue? > > diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c > index 2b09f0bd8432..94b3d049fe9d 100644 > --- a/arch/riscv/kernel/setup.c > +++ b/arch/riscv/kernel/setup.c > @@ -277,14 +277,15 @@ void __init setup_arch(char **cmdline_p) > paging_init(); > #if IS_ENABLED(CONFIG_BUILTIN_DTB) > initial_boot_params = __va(XIP_FIXUP(dtb_early_pa)); > + early_init_fdt_scan_reserved_mem(); > unflatten_and_copy_device_tree(); > #else > - if (early_init_dt_verify(__va(XIP_FIXUP(dtb_early_pa)))) > + if (early_init_dt_verify(__va(XIP_FIXUP(dtb_early_pa)))) { > + early_init_fdt_scan_reserved_mem(); > unflatten_device_tree(); > - else > + } else > pr_err("No DTB found in kernel mappings\n"); > #endif > - early_init_fdt_scan_reserved_mem(); > misc_mem_init(); > > init_resources(); > > > >> >> Obviously, both of these changes are moving the function call in >> opposite directions and we can only really do one of them. We are not >> sure if what we are doing with the non-cached reserved-memory section >> is just not permitted & cannot work - or if this is something that >> was overlooked for RISC-V specifically and works for other archs. >> >> It does seem like the first issue is a real bug, and I am happy to >> submit the patch for that whenever - but having two problems with >> opposite fixes seemed as if there was something else lurking that we >> just don't have enough understanding to detect. >> >> Any help would be great! >> >> Thanks, >> Conor. >> > > Even if that does not fix your issue, the first patch is necessary as > it fixes initial_boot_params. > > >> >> >> _______________________________________________ >> linux-riscv mailing list >> linux-riscv@lists.infradead.org >> http://lists.infradead.org/mailman/listinfo/linux-riscv
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