Re: [PATCH 1/2] arm64: mm: Do not defer reserve_crashkernel() if only ZONE_DMA32

[Kefeng Wang]

On 2022/3/30 6:29, Vijay Balakrishna wrote:
> On 3/24/2022 10:53 PM, Kefeng Wang wrote:
> > The kernel could be benifit due to BLOCK_MAPPINGS, see commit
> > 031495635b46 ("arm64: Do not defer reserve_crashkernel() for
> > platforms with no DMA memory zones"), if there is only with
> > ZONE_DMA32, we could set arm64_dma_phys_limit to max_zone_phys(32)
> > earlier in arm64_memblock_init(), then we will benifit too.
>
> Thanks for noticing platforms with just ZONE_DMA32 config can also 
> benefit BLOCK_MAPPINGS.  I assume you have access to one where you 
> notice the difference with proposed changes and able to test.  I did 
> test proposed changes on SoC we use with IOMMU (no ZONE_DMA configs 
> enabled).
I backported your patches into 5.10 and tested(unixbench will benifit 
due to block mapping, only with DMA32 and rodata=false)
> Nits --
> - benifit -> benefit
> - consider making commit message clear, "then we will.." seems you are 
> referring to platforms with just ZONE_DMA32 config enabled
> - to reflect new change consider updating comment added in commit 
> 031495635b46
Thanks for your reviewing,  will update and test with upstream.
> > Cc: Vijay Balakrishna <vijayb@xxxxxxxxxxxxxxxxxxx>
> > Cc: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>
> > Cc: Will Deacon <will@xxxxxxxxxx>
> > Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
>
> Reviewed-by: Vijay Balakrishna <vijayb@xxxxxxxxxxxxxxxxxxx>
>
> > ---
> >   arch/arm64/mm/init.c | 18 ++++++++++--------
> >   arch/arm64/mm/mmu.c  |  6 ++----
> >   2 files changed, 12 insertions(+), 12 deletions(-)
> >
> > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> > index 8ac25f19084e..9dded8779d72 100644
> > --- a/arch/arm64/mm/init.c
> > +++ b/arch/arm64/mm/init.c
> > @@ -157,14 +157,14 @@ static phys_addr_t __init 
> > max_zone_phys(unsigned int zone_bits)
> >       return min(zone_mask, memblock_end_of_DRAM() - 1) + 1;
> >   }
> >   +phys_addr_t __ro_after_init dma32_phys_limit;
Will make it static, suggested by Florian
> >   static void __init zone_sizes_init(unsigned long min, unsigned long 
> > max)
> >   {
> >       unsigned long max_zone_pfns[MAX_NR_ZONES]  = {0};
> > -    unsigned int __maybe_unused acpi_zone_dma_bits;
> > -    unsigned int __maybe_unused dt_zone_dma_bits;
> > -    phys_addr_t __maybe_unused dma32_phys_limit = max_zone_phys(32);
> > -
> >   #ifdef CONFIG_ZONE_DMA
> > +    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);
> > @@ -173,8 +173,6 @@ static void __init zone_sizes_init(unsigned long 
> > min, unsigned long max)
> >   #endif
> >   #ifdef CONFIG_ZONE_DMA32
> >       max_zone_pfns[ZONE_DMA32] = PFN_DOWN(dma32_phys_limit);
> > -    if (!arm64_dma_phys_limit)
> > -        arm64_dma_phys_limit = dma32_phys_limit;
> >   #endif
> >       max_zone_pfns[ZONE_NORMAL] = max;
> >   @@ -336,8 +334,12 @@ void __init arm64_memblock_init(void)
> >         early_init_fdt_scan_reserved_mem();
> >   -    if (!IS_ENABLED(CONFIG_ZONE_DMA) && 
> > !IS_ENABLED(CONFIG_ZONE_DMA32))
> > +    dma32_phys_limit = max_zone_phys(32);
> > +    if (!IS_ENABLED(CONFIG_ZONE_DMA)) {
> > +        if (IS_ENABLED(CONFIG_ZONE_DMA32))
> > +            arm64_dma_phys_limit = dma32_phys_limit;
> >           reserve_crashkernel();
> > +    }
> >         high_memory = __va(memblock_end_of_DRAM() - 1) + 1;
> >   }
> > @@ -385,7 +387,7 @@ 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) || IS_ENABLED(CONFIG_ZONE_DMA32))
> > +    if (IS_ENABLED(CONFIG_ZONE_DMA))
> >           reserve_crashkernel();
> >         memblock_dump_all();
> > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> > index 626ec32873c6..23734481318a 100644
> > --- a/arch/arm64/mm/mmu.c
> > +++ b/arch/arm64/mm/mmu.c
> > @@ -529,8 +529,7 @@ static void __init map_mem(pgd_t *pgdp)
> >     #ifdef CONFIG_KEXEC_CORE
> >       if (crash_mem_map) {
> > -        if (IS_ENABLED(CONFIG_ZONE_DMA) ||
> > -            IS_ENABLED(CONFIG_ZONE_DMA32))
> > +        if (IS_ENABLED(CONFIG_ZONE_DMA))
> >               flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
> >           else if (crashk_res.end)
> >               memblock_mark_nomap(crashk_res.start,
> > @@ -571,8 +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) && 
> > !IS_ENABLED(CONFIG_ZONE_DMA32)) {
> > +    if (crash_mem_map && !IS_ENABLED(CONFIG_ZONE_DMA)) {
> >           if (crashk_res.end) {
> >               __map_memblock(pgdp, crashk_res.start,
> >                          crashk_res.end + 1,
> .