Re: [PATCH v3 5/6] sparc32: move early memory setup to setup_arch

[Magnus Lindholm]

Hi Andreas,

On Fri, Sep 25, 2026 at 5:58 PM Andreas Larsson <andreas@xxxxxxxxxxx> wrote:
>
> On 2026-09-01 23:45, Magnus Lindholm wrote:
> > Move the early memory configuration out of SRMMU paging setup and next to
> > the rest of setup_arch(). Derive the PFN limits from memblock, reserve the
> > kernel and initrd there, and retain mem= support with
> > memblock_enforce_memory_limit().
> >
> > Use for_each_mem_pfn_range() to find the lowmem boundary and replace
> > last_valid_pfn with the standard max_low_pfn variable. Set the standard
> > max_pfn variable to the end of physical memory and use it as the highmem
> > zone limit. This tightens LEON's _pfn_valid() upper bound from all RAM to
> > the lowmem limit, with no functional change because LEON does not use
> > highmem.
>
> It is not at all true that LEON systems do not use highmem. Rather, they
> can make heavy use of highmen. Continued further down.
>
>

Oh, yeah you're right, I'll remove the incorrect statement that LEON does
not use highmem.

> > The removed bootmem code also printed a private HIGHMEM summary. Generic
> > memory initialization already reports the highmem zone, so do not retain
> > the duplicate message.
> >
> > When PAGE_OFFSET maps a relocated kernel, remove memory below phys_base
> > from memblock because it cannot be reached through the linear map. This
> > replaces the equivalent trimming of sp_banks.
> >
> > Suggested-by: Sam Ravnborg <sam@xxxxxxxxxxxx>
> > Signed-off-by: Magnus Lindholm <linmag7@xxxxxxxxx>
> > ---
> >  arch/sparc/include/asm/highmem.h    |   3 -
> >  arch/sparc/include/asm/leon.h       |   2 +-
> >  arch/sparc/include/asm/pgtable_32.h |   3 +-
> >  arch/sparc/include/asm/pgtsrmmu.h   |   1 -
> >  arch/sparc/kernel/setup_32.c        | 112 ++++++++++++-----------
> >  arch/sparc/mm/init_32.c             | 132 +---------------------------
> >  arch/sparc/mm/leon_mm.c             |   1 +
> >  arch/sparc/mm/srmmu.c               |   8 +-
> >  8 files changed, 67 insertions(+), 195 deletions(-)
> >
> > diff --git a/arch/sparc/include/asm/highmem.h b/arch/sparc/include/asm/highmem.h
> > index c7b2e208328b..b1b915ac604d 100644
> > --- a/arch/sparc/include/asm/highmem.h
> > +++ b/arch/sparc/include/asm/highmem.h
> > @@ -26,9 +26,6 @@
> >  #include <asm/vaddrs.h>
> >  #include <asm/pgtsrmmu.h>
> >
> > -/* declarations for highmem.c */
> > -extern unsigned long highstart_pfn, highend_pfn;
> > -
> >  #define kmap_prot __pgprot(SRMMU_ET_PTE | SRMMU_PRIV | SRMMU_CACHE)
> >  extern pte_t *pkmap_page_table;
> >
> > diff --git a/arch/sparc/include/asm/leon.h b/arch/sparc/include/asm/leon.h
> > index 053a24b67aed..815131c77ed7 100644
> > --- a/arch/sparc/include/asm/leon.h
> > +++ b/arch/sparc/include/asm/leon.h
> > @@ -251,7 +251,7 @@ extern int leon_ipi_irq;
> >
> >  /* macros used in leon_mm.c */
> >  #define PFN(x)           ((x) >> PAGE_SHIFT)
> > -#define _pfn_valid(pfn)       ((pfn < last_valid_pfn) && (pfn >= PFN(phys_base)))
> > +#define _pfn_valid(pfn)       ((pfn < max_low_pfn) && (pfn >= PFN(phys_base)))
>
> What is the reason for doing this change? When leon_swprobe() is called
> max_pfn has already been set up. Is there a reason for not using that?
>
>
> However, in the scope of the calls to leon_swprobe(), no parts of the
> inherited MMU table's PTDs/PTEs are outside of lowmem. If there indeed
> is some technical reason for needing to do this change I suggest that
> you, in a separate patch before this one:
>
> - Remove PFN() and replace the callers in leon_mm.c with the standard
>   PFN_DOWN() instead, as also Sam lifted as "future work", and
>
> - Move the _pfn_valid define to leon_mm.c, make it only check for lowmem
>   pfns and rename it to _pfn_lowmem() or something like that.
>

Thanks, you are right: last_valid_pfn previously held the value of max_pfn, so
changing the upper bound to max_low_pfn was incorrect and could reject valid
LEON highmem PFNs.

> >  #define _SRMMU_PTE_PMASK_LEON 0xffffffff
> >
> >  /*
> > diff --git a/arch/sparc/include/asm/pgtable_32.h b/arch/sparc/include/asm/pgtable_32.h
> > index f89b1250661d..91a6032cf6a2 100644
> > --- a/arch/sparc/include/asm/pgtable_32.h
> > +++ b/arch/sparc/include/asm/pgtable_32.h
> > @@ -37,8 +37,7 @@ struct vm_area_struct;
> >  struct page;
> >
> >  void load_mmu(void);
> > -unsigned long calc_highpages(void);
> > -unsigned long __init bootmem_init(unsigned long *pages_avail);
> > +void __init find_ramdisk(unsigned long end_of_phys_memory);
> >
> >  #define pte_ERROR(e)   __builtin_trap()
> >  #define pmd_ERROR(e)   __builtin_trap()
> > diff --git a/arch/sparc/include/asm/pgtsrmmu.h b/arch/sparc/include/asm/pgtsrmmu.h
> > index a265822a475e..a2a6c8564c3e 100644
> > --- a/arch/sparc/include/asm/pgtsrmmu.h
> > +++ b/arch/sparc/include/asm/pgtsrmmu.h
> > @@ -98,7 +98,6 @@
> >        restore %g0, %g0, %g0;
> >
> >  #ifndef __ASSEMBLER__
> > -extern unsigned long last_valid_pfn;
> >
> >  /* This makes sense. Honest it does - Anton */
> >  /* XXX Yes but it's ugly as sin.  FIXME. -KMW */
> > diff --git a/arch/sparc/kernel/setup_32.c b/arch/sparc/kernel/setup_32.c
> > index 795714959da6..6ad85538964d 100644
> > --- a/arch/sparc/kernel/setup_32.c
> > +++ b/arch/sparc/kernel/setup_32.c
> > @@ -23,6 +23,7 @@
> >  #include <linux/syscalls.h>
> >  #include <linux/kdev_t.h>
> >  #include <linux/major.h>
> > +#include <linux/memblock.h>
> >  #include <linux/string.h>
> >  #include <linux/init.h>
> >  #include <linux/interrupt.h>
> > @@ -254,28 +255,71 @@ static __init void leon_patch(void)
> >
> >  struct tt_entry *sparc_ttable;
> >
> > -/* Drop RAM below the kernel; the linear map runs upward from phys_base
> > - * and cannot reach it.
> > - */
> > -static void __init trim_sp_banks_below(unsigned long base)
> > +unsigned long phys_base;
> > +EXPORT_SYMBOL(phys_base);
> > +
> > +unsigned long pfn_base;
> > +EXPORT_SYMBOL(pfn_base);
> > +
> > +static unsigned long __init calc_max_low_pfn(void)
> >  {
> > -     int i, j = 0;
> > +     unsigned long limit = pfn_base + PHYS_PFN(SRMMU_MAXMEM);
> > +     unsigned long start_pfn, end_pfn;
> > +     unsigned long last_pfn = 0;
> > +     int i;
> > +
> > +     for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, NULL) {
> > +             if (start_pfn >= limit) {
> > +                     if (last_pfn < limit)
> > +                             limit = last_pfn;
> > +                     break;
> > +             }
> >
> > -     for (i = 0; sp_banks[i].num_bytes != 0; i++) {
> > -             unsigned long start = sp_banks[i].base_addr;
> > -             unsigned long end = start + sp_banks[i].num_bytes;
> > +             last_pfn = end_pfn;
> > +     }
> >
> > -             if (end <= base)
> > -                     continue;               /* wholly below - drop it */
> > -             if (start < base)
> > -                     start = base;           /* straddles - trim the front */
> > +     return limit;
> > +}
> >
> > -             sp_banks[j].base_addr = start;
> > -             sp_banks[j].num_bytes = end - start;
> > -             j++;
> > +static void __init setup_memory(void)
> > +{
> > +     unsigned long ram_base = memblock_start_of_DRAM();
> > +     unsigned long real_base = __get_phys(PAGE_OFFSET);
> > +     unsigned long size;
> > +
> > +     memblock_set_bottom_up(true);
> > +     memblock_allow_resize();
> > +
> > +     phys_base = ram_base;
> > +     if (real_base && real_base != phys_base) {
> > +             prom_printf("phys_base: RAM starts 0x%x but kernel is at 0x%x\n",
> > +                         (unsigned int)phys_base, (unsigned int)real_base);
> > +             phys_base = real_base;
> > +             memblock_remove(0, phys_base);
> > +             prom_printf("phys_base: adopted 0x%x, RAM below it dropped\n",
> > +                         (unsigned int)phys_base);
> >       }
> > -     sp_banks[j].base_addr = 0;
> > -     sp_banks[j].num_bytes = 0;
> > +
> > +     if (cmdline_memory_size)
> > +             memblock_enforce_memory_limit(cmdline_memory_size);
> > +
> > +     min_low_pfn = PFN_DOWN(memblock_start_of_DRAM());
> > +     pfn_base = PHYS_PFN(phys_base);
> > +     max_pfn = PFN_DOWN(memblock_end_of_DRAM());
> > +     max_low_pfn = max_pfn;
> > +
> > +     if (max_low_pfn > pfn_base + PHYS_PFN(SRMMU_MAXMEM))
> > +             max_low_pfn = calc_max_low_pfn();
> > +
> > +     find_ramdisk(memblock_end_of_DRAM());
> > +
> > +     /* Reserve the kernel text/data/bss. */
> > +     size = __pa(PAGE_ALIGN((unsigned long)&_end)) - phys_base;
> > +     memblock_reserve(phys_base, size);
> > +     memblock_add(phys_base, size);
> > +
> > +     /* Only allow low memory to be allocated by memblock. */
> > +     memblock_set_current_limit(PFN_PHYS(max_low_pfn));
> >  }
> >
> >  /* Called from head_32.S - before we have setup anything
> > @@ -306,9 +350,6 @@ void __init sparc32_start_kernel(struct linux_romvec *rp)
> >
> >  void __init setup_arch(char **cmdline_p)
> >  {
> > -     int i;
> > -     unsigned long highest_paddr;
> > -
> >       sparc_ttable = &trapbase[0];
> >
> >       /* Initialize PROM console and command line. */
> > @@ -343,36 +384,7 @@ void __init setup_arch(char **cmdline_p)
> >
> >       idprom_init();
> >       load_mmu();
> > -
> > -     phys_base = 0xffffffffUL;
> > -     highest_paddr = 0UL;
> > -     for (i = 0; sp_banks[i].num_bytes != 0; i++) {
> > -             unsigned long top;
> > -
> > -             if (sp_banks[i].base_addr < phys_base)
> > -                     phys_base = sp_banks[i].base_addr;
> > -             top = sp_banks[i].base_addr +
> > -                     sp_banks[i].num_bytes;
> > -             if (highest_paddr < top)
> > -                     highest_paddr = top;
> > -     }
> > -
> > -     /* phys_base must describe what PAGE_OFFSET maps to, not where RAM starts. */
> > -     {
> > -             unsigned long real_base = __get_phys(PAGE_OFFSET);
> > -
> > -             if (real_base && real_base != phys_base) {
> > -                     prom_printf("phys_base: RAM starts 0x%x but kernel is at 0x%x\n",
> > -                                 (unsigned int)phys_base,
> > -                                 (unsigned int)real_base);
> > -                     phys_base = real_base;
> > -                     trim_sp_banks_below(phys_base);
> > -                     prom_printf("phys_base: adopted 0x%x, RAM below it dropped\n",
> > -                                 (unsigned int)phys_base);
> > -             }
> > -     }
> > -
> > -     pfn_base = phys_base >> PAGE_SHIFT;
> > +     setup_memory();
> >
> >       if (!root_flags)
> >               root_mountflags &= ~MS_RDONLY;
> > diff --git a/arch/sparc/mm/init_32.c b/arch/sparc/mm/init_32.c
> > index 6880d9cb30a5..ac4462f1cf76 100644
> > --- a/arch/sparc/mm/init_32.c
> > +++ b/arch/sparc/mm/init_32.c
> > @@ -35,66 +35,13 @@
> >
> >  #include "mm_32.h"
> >
> > -unsigned long phys_base;
> > -EXPORT_SYMBOL(phys_base);
> > -
> > -unsigned long pfn_base;
> > -EXPORT_SYMBOL(pfn_base);
> > -
> >  struct sparc_phys_banks sp_banks[SPARC_PHYS_BANKS+1];
> >
> >  /* Initial ramdisk setup */
> >  extern unsigned int sparc_ramdisk_image;
> >  extern unsigned int sparc_ramdisk_size;
> >
> > -unsigned long highstart_pfn, highend_pfn;
> > -
> > -unsigned long last_valid_pfn;
> > -
> > -unsigned long calc_highpages(void)
> > -{
> > -     int i;
> > -     int nr = 0;
> > -
> > -     for (i = 0; sp_banks[i].num_bytes != 0; i++) {
> > -             unsigned long start_pfn = sp_banks[i].base_addr >> PAGE_SHIFT;
> > -             unsigned long end_pfn = (sp_banks[i].base_addr + sp_banks[i].num_bytes) >> PAGE_SHIFT;
> > -
> > -             if (end_pfn <= max_low_pfn)
> > -                     continue;
> > -
> > -             if (start_pfn < max_low_pfn)
> > -                     start_pfn = max_low_pfn;
> > -
> > -             nr += end_pfn - start_pfn;
> > -     }
> > -
> > -     return nr;
> > -}
> > -
> > -static unsigned long calc_max_low_pfn(void)
> > -{
> > -     int i;
> > -     unsigned long tmp = pfn_base + (SRMMU_MAXMEM >> PAGE_SHIFT);
> > -     unsigned long curr_pfn, last_pfn;
> > -
> > -     last_pfn = (sp_banks[0].base_addr + sp_banks[0].num_bytes) >> PAGE_SHIFT;
> > -     for (i = 1; sp_banks[i].num_bytes != 0; i++) {
> > -             curr_pfn = sp_banks[i].base_addr >> PAGE_SHIFT;
> > -
> > -             if (curr_pfn >= tmp) {
> > -                     if (last_pfn < tmp)
> > -                             tmp = last_pfn;
> > -                     break;
> > -             }
> > -
> > -             last_pfn = (sp_banks[i].base_addr + sp_banks[i].num_bytes) >> PAGE_SHIFT;
> > -     }
> > -
> > -     return tmp;
> > -}
> > -
> > -static void __init find_ramdisk(unsigned long end_of_phys_memory)
> > +void __init find_ramdisk(unsigned long end_of_phys_memory)
> >  {
> >  #ifdef CONFIG_BLK_DEV_INITRD
> >       unsigned long size;
> > @@ -124,83 +71,6 @@ static void __init find_ramdisk(unsigned long end_of_phys_memory)
> >  #endif
> >  }
> >
> > -unsigned long __init bootmem_init(unsigned long *pages_avail)
> > -{
> > -     unsigned long start_pfn, bytes_avail, size;
> > -     unsigned long end_of_phys_memory = 0;
> > -     unsigned long high_pages = 0;
> > -     int i;
> > -
> > -     memblock_set_bottom_up(true);
> > -     memblock_allow_resize();
> > -
> > -     bytes_avail = 0UL;
> > -     for (i = 0; sp_banks[i].num_bytes != 0; i++) {
> > -             end_of_phys_memory = sp_banks[i].base_addr +
> > -                     sp_banks[i].num_bytes;
> > -             bytes_avail += sp_banks[i].num_bytes;
> > -             if (cmdline_memory_size) {
> > -                     if (bytes_avail > cmdline_memory_size) {
> > -                             unsigned long slack = bytes_avail - cmdline_memory_size;
> > -
> > -                             bytes_avail -= slack;
> > -                             end_of_phys_memory -= slack;
> > -
> > -                             sp_banks[i].num_bytes -= slack;
> > -                             if (sp_banks[i].num_bytes == 0) {
> > -                                     sp_banks[i].base_addr = 0xdeadbeef;
> > -                             } else {
> > -                                     memblock_add(sp_banks[i].base_addr,
> > -                                                  sp_banks[i].num_bytes);
> > -                                     sp_banks[i+1].num_bytes = 0;
> > -                                     sp_banks[i+1].base_addr = 0xdeadbeef;
> > -                             }
> > -                             break;
> > -                     }
> > -             }
> > -             memblock_add(sp_banks[i].base_addr, sp_banks[i].num_bytes);
> > -     }
> > -
> > -     if (cmdline_memory_size)
> > -             memblock_enforce_memory_limit(cmdline_memory_size);
> > -
> > -     /* Start with page aligned address of last symbol in kernel
> > -      * image.
> > -      */
> > -     start_pfn  = (unsigned long)__pa(PAGE_ALIGN((unsigned long) &_end));
> > -
> > -     /* Now shift down to get the real physical page frame number. */
> > -     start_pfn >>= PAGE_SHIFT;
> > -
> > -     max_pfn = end_of_phys_memory >> PAGE_SHIFT;
> > -
> > -     max_low_pfn = max_pfn;
> > -     highstart_pfn = highend_pfn = max_pfn;
> > -
> > -     if (max_low_pfn > pfn_base + (SRMMU_MAXMEM >> PAGE_SHIFT)) {
> > -             highstart_pfn = pfn_base + (SRMMU_MAXMEM >> PAGE_SHIFT);
> > -             max_low_pfn = calc_max_low_pfn();
> > -             high_pages = calc_highpages();
> > -             printk(KERN_NOTICE "%ldMB HIGHMEM available.\n",
> > -                 high_pages >> (20 - PAGE_SHIFT));
> > -     }
> > -
> > -     find_ramdisk(end_of_phys_memory);
> > -
> > -     /* Reserve the kernel text/data/bss. */
> > -     size = (start_pfn << PAGE_SHIFT) - phys_base;
> > -     memblock_reserve(phys_base, size);
> > -     memblock_add(phys_base, size);
> > -
> > -     size = memblock_phys_mem_size() - memblock_reserved_size();
> > -     *pages_avail = (size >> PAGE_SHIFT) - high_pages;
> > -
> > -     /* Only allow low memory to be allocated via memblock allocation */
> > -     memblock_set_current_limit(max_low_pfn << PAGE_SHIFT);
> > -
> > -     return max_pfn;
> > -}
> > -
> >  /*
> >   * paging_init() sets up the page tables: We call the MMU specific
> >   * init routine based upon the Sun model type on the Sparc.
> > diff --git a/arch/sparc/mm/leon_mm.c b/arch/sparc/mm/leon_mm.c
> > index 1dc9b3d70eda..a43c5ffbbbe5 100644
> > --- a/arch/sparc/mm/leon_mm.c
> > +++ b/arch/sparc/mm/leon_mm.c
> > @@ -11,6 +11,7 @@
> >   */
> >
> >  #include <linux/kernel.h>
> > +#include <linux/memblock.h>
> >  #include <linux/mm.h>
> >  #include <asm/asi.h>
> >  #include <asm/leon.h>
> > diff --git a/arch/sparc/mm/srmmu.c b/arch/sparc/mm/srmmu.c
> > index f094f6c105a2..e333d3eac451 100644
> > --- a/arch/sparc/mm/srmmu.c
> > +++ b/arch/sparc/mm/srmmu.c
> > @@ -59,8 +59,6 @@ int vac_line_size;
> >
> >  extern struct resource sparc_iomap;
> >
> > -extern unsigned long last_valid_pfn;
> > -
> >  static pgd_t *srmmu_swapper_pg_dir;
> >
> >  const struct sparc32_cachetlb_ops *sparc32_cachetlb_ops;
> > @@ -871,7 +869,7 @@ void __init arch_zone_limits_init(unsigned long *max_zone_pfns)
> >  {
> >       max_zone_pfns[ZONE_DMA] = max_low_pfn;
> >       max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
> > -     max_zone_pfns[ZONE_HIGHMEM] = highend_pfn;
> > +     max_zone_pfns[ZONE_HIGHMEM] = max_pfn;
> >  }
> >
> >  void __init srmmu_paging_init(void)
> > @@ -884,7 +882,6 @@ void __init srmmu_paging_init(void)
> >       pud_t *pud;
> >       pmd_t *pmd;
> >       pte_t *pte;
> > -     unsigned long pages_avail;
> >
> >       init_mm.context = (unsigned long) NO_CONTEXT;
> >       sparc_iomap.start = SUN4M_IOBASE_VADDR; /* 16MB of IOSPACE on all sun4m's. */
> > @@ -910,9 +907,6 @@ void __init srmmu_paging_init(void)
> >               prom_halt();
> >       }
> >
> > -     pages_avail = 0;
> > -     last_valid_pfn = bootmem_init(&pages_avail);
> > -
> >       srmmu_nocache_calcsize();
> >       srmmu_nocache_init();
> >       srmmu_inherit_prom_mappings(0xfe400000, (LINUX_OPPROM_ENDVM - PAGE_SIZE));
>
> Thanks,
> Andreas
>

Thanks Andreas for taking the time to go over this patch,
I'll put out a v4 based on your feedback, asap.

Magnus