Messages in this thread Patch in this message | | | Date | Fri, 1 Apr 2022 15:09:03 -0700 | Subject | Re: [PATCH v2 resend 2/3] arm64: mm: Don't defer reserve_crashkernel() with dma_force_32bit | From | Vijay Balakrishna <> |
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On 3/31/2022 12:40 AM, Kefeng Wang wrote: > ARM64 enable ZONE_DMA by default, and with ZONE_DMA crash kernel > memory reservation is delayed until DMA zone memory range size > initilazation performed in zone_sizes_init(), but for most platforms > use 32bit dma_zone_bits, so add dma_force_32bit kernel parameter > if ZONE_DMA enabled, and initialize arm64_dma_phys_limit to > dma32_phys_limit in arm64_memblock_init() if dma_force_32bit > is setup, this could let the crash kernel reservation earlier, > and allows linear creation with block mapping. > > Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
I don't see any problem with the approach. Hope you or someone can test to make sure no surprises on RPi4 with the proposed change. I do understand on RPi4 --
- both ZONE_DMA and ZONE_DMA32 are enabled - one wouldn't use dma_force_32bit kernel parameter - crashkernel_could_early_reserve() would return false to preserve late reserve of crash kernel memory
nit -- - consider renaming crashkernel_could_early_reserve() => crashkernel_early_reserve()
Reviewed-by: Vijay Balakrishna <vijayb@linux.microsoft.com>
> --- > arch/arm64/include/asm/kexec.h | 1 + > arch/arm64/mm/init.c | 42 ++++++++++++++++++++++++++-------- > arch/arm64/mm/mmu.c | 4 ++-- > 3 files changed, 36 insertions(+), 11 deletions(-) > > diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h > index 9839bfc163d7..8bea40aea359 100644 > --- a/arch/arm64/include/asm/kexec.h > +++ b/arch/arm64/include/asm/kexec.h > @@ -95,6 +95,7 @@ void cpu_soft_restart(unsigned long el2_switch, unsigned long entry, > unsigned long arg0, unsigned long arg1, > unsigned long arg2); > #endif > +bool crashkernel_could_early_reserve(void); > > #define ARCH_HAS_KIMAGE_ARCH > > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > index fb01eb489fa9..0aafa9181607 100644 > --- a/arch/arm64/mm/init.c > +++ b/arch/arm64/mm/init.c > @@ -66,7 +66,8 @@ EXPORT_SYMBOL(memstart_addr); > * depending on DMA memory zones configs (ZONE_DMA) -- > * > * In absence of ZONE_DMA and ZONE_DMA32 configs arm64_dma_phys_limit > - * initialized here and if only with ZONE_DMA32 arm64_dma_phys_limit > + * initialized here, and if only with ZONE_DMA32 or if with ZONE_DMA > + * and dma_force_32bit kernel parameter, the arm64_dma_phys_limit is > * initialised to dma32_phys_limit. This lets early reservation of > * crash kernel memory which has a dependency on arm64_dma_phys_limit. > * Reserving memory early for crash kernel allows linear creation of block > @@ -92,6 +93,27 @@ phys_addr_t __ro_after_init arm64_dma_phys_limit; > phys_addr_t __ro_after_init arm64_dma_phys_limit = PHYS_MASK + 1; > #endif > > +static bool __ro_after_init arm64_dma_force_32bit; > +#ifdef CONFIG_ZONE_DMA > +static int __init arm64_dma_force_32bit_setup(char *p) > +{ > + zone_dma_bits = 32; > + arm64_dma_force_32bit = true; > + > + return 0; > +} > +early_param("dma_force_32bit", arm64_dma_force_32bit_setup); > +#endif > + > +bool __init crashkernel_could_early_reserve(void) > +{ > + if (!IS_ENABLED(CONFIG_ZONE_DMA)) > + return true; > + if (arm64_dma_force_32bit) > + return true; > + return false; > +} > + > /* > * reserve_crashkernel() - reserves memory for crash kernel > * > @@ -163,12 +185,14 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max) > { > unsigned long max_zone_pfns[MAX_NR_ZONES] = {0}; > #ifdef CONFIG_ZONE_DMA > - unsigned int acpi_zone_dma_bits; > - unsigned int dt_zone_dma_bits; > + if (!arm64_dma_force_32bit) { > + unsigned int acpi_zone_dma_bits; > + unsigned int dt_zone_dma_bits; > > - acpi_zone_dma_bits = fls64(acpi_iort_dma_get_max_cpu_address()); > - dt_zone_dma_bits = fls64(of_dma_get_max_cpu_address(NULL)); > - zone_dma_bits = min3(32U, dt_zone_dma_bits, acpi_zone_dma_bits); > + acpi_zone_dma_bits = fls64(acpi_iort_dma_get_max_cpu_address()); > + dt_zone_dma_bits = fls64(of_dma_get_max_cpu_address(NULL)); > + zone_dma_bits = min3(32U, dt_zone_dma_bits, acpi_zone_dma_bits); > + } > arm64_dma_phys_limit = max_zone_phys(zone_dma_bits); > max_zone_pfns[ZONE_DMA] = PFN_DOWN(arm64_dma_phys_limit); > #endif > @@ -336,8 +360,8 @@ void __init arm64_memblock_init(void) > early_init_fdt_scan_reserved_mem(); > > dma32_phys_limit = max_zone_phys(32); > - if (!IS_ENABLED(CONFIG_ZONE_DMA)) { > - if (IS_ENABLED(CONFIG_ZONE_DMA32)) > + if (crashkernel_could_early_reserve()) { > + if (IS_ENABLED(CONFIG_ZONE_DMA32) || arm64_dma_force_32bit) > arm64_dma_phys_limit = dma32_phys_limit; > reserve_crashkernel(); > } > @@ -388,7 +412,7 @@ void __init bootmem_init(void) > * request_standard_resources() depends on crashkernel's memory being > * reserved, so do it here. > */ > - if (IS_ENABLED(CONFIG_ZONE_DMA)) > + if (!crashkernel_could_early_reserve()) > reserve_crashkernel(); > > memblock_dump_all(); > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index 23734481318a..8f7e8452d906 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -529,7 +529,7 @@ static void __init map_mem(pgd_t *pgdp) > > #ifdef CONFIG_KEXEC_CORE > if (crash_mem_map) { > - if (IS_ENABLED(CONFIG_ZONE_DMA)) > + if (!crashkernel_could_early_reserve()) > flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS; > else if (crashk_res.end) > memblock_mark_nomap(crashk_res.start, > @@ -570,7 +570,7 @@ static void __init map_mem(pgd_t *pgdp) > * through /sys/kernel/kexec_crash_size interface. > */ > #ifdef CONFIG_KEXEC_CORE > - if (crash_mem_map && !IS_ENABLED(CONFIG_ZONE_DMA)) { > + if (crash_mem_map && crashkernel_could_early_reserve()) { > if (crashk_res.end) { > __map_memblock(pgdp, crashk_res.start, > crashk_res.end + 1,
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