From: Chengkaitao <chengkaitao@kylinos.cn>
1. In the SPARC architecture, reimplemented vmemmap_populate using
vmemmap_populate_hugepages.
2. Allow the SPARC arch to fallback to vmemmap_populate_basepages(),
when vmemmap_alloc_block returns NULL.
Signed-off-by: Chengkaitao <chengkaitao@kylinos.cn>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
arch/sparc/mm/init_64.c | 47 ++++++++++++++---------------------------
1 file changed, 16 insertions(+), 31 deletions(-)
diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
index df9f7c444c39..858eaa6615ea 100644
--- a/arch/sparc/mm/init_64.c
+++ b/arch/sparc/mm/init_64.c
@@ -2581,8 +2581,8 @@ unsigned long _PAGE_CACHE __read_mostly;
EXPORT_SYMBOL(_PAGE_CACHE);
#ifdef CONFIG_SPARSEMEM_VMEMMAP
-int __meminit vmemmap_populate(unsigned long vstart, unsigned long vend,
- int node, struct vmem_altmap *altmap)
+void __meminit vmemmap_set_pmd(pmd_t *pmd, void *p, int node,
+ unsigned long addr, unsigned long next)
{
unsigned long pte_base;
@@ -2595,39 +2595,24 @@ int __meminit vmemmap_populate(unsigned long vstart, unsigned long vend,
pte_base |= _PAGE_PMD_HUGE;
- vstart = vstart & PMD_MASK;
- vend = ALIGN(vend, PMD_SIZE);
- for (; vstart < vend; vstart += PMD_SIZE) {
- pgd_t *pgd = vmemmap_pgd_populate(vstart, node);
- unsigned long pte;
- p4d_t *p4d;
- pud_t *pud;
- pmd_t *pmd;
-
- if (!pgd)
- return -ENOMEM;
-
- p4d = vmemmap_p4d_populate(pgd, vstart, node);
- if (!p4d)
- return -ENOMEM;
-
- pud = vmemmap_pud_populate(p4d, vstart, node);
- if (!pud)
- return -ENOMEM;
+ pmd_val(*pmd) = pte_base | __pa(p);
+}
- pmd = pmd_offset(pud, vstart);
- pte = pmd_val(*pmd);
- if (!(pte & _PAGE_VALID)) {
- void *block = vmemmap_alloc_block(PMD_SIZE, node);
+int __meminit vmemmap_check_pmd(pmd_t *pmdp, int node,
+ unsigned long addr, unsigned long next)
+{
+ int large = pmd_leaf(*pmdp);
- if (!block)
- return -ENOMEM;
+ if (large)
+ vmemmap_verify((pte_t *)pmdp, node, addr, next);
- pmd_val(*pmd) = pte_base | __pa(block);
- }
- }
+ return large;
+}
- return 0;
+int __meminit vmemmap_populate(unsigned long vstart, unsigned long vend,
+ int node, struct vmem_altmap *altmap)
+{
+ return vmemmap_populate_hugepages(vstart, vend, node, altmap);
}
#endif /* CONFIG_SPARSEMEM_VMEMMAP */
--
2.50.1 (Apple Git-155)On 2026-01-11 08:44, chengkaitao wrote:
> From: Chengkaitao <chengkaitao@kylinos.cn>
>
> 1. In the SPARC architecture, reimplemented vmemmap_populate using
> vmemmap_populate_hugepages.
> 2. Allow the SPARC arch to fallback to vmemmap_populate_basepages(),
> when vmemmap_alloc_block returns NULL.
This patch seems to potentially make more functional changes than what
the descriptions gives impression of.
Given the amount of changes this seems to introduce, more on that below,
I'd like to see more description on the changes and why they can be done
than this.
Nit: use active language, "reimplement", not "reimplemented".
> Signed-off-by: Chengkaitao <chengkaitao@kylinos.cn>
> Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> ---
> arch/sparc/mm/init_64.c | 47 ++++++++++++++---------------------------
> 1 file changed, 16 insertions(+), 31 deletions(-)
>
> diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
> index df9f7c444c39..858eaa6615ea 100644
> --- a/arch/sparc/mm/init_64.c
> +++ b/arch/sparc/mm/init_64.c
> @@ -2581,8 +2581,8 @@ unsigned long _PAGE_CACHE __read_mostly;
> EXPORT_SYMBOL(_PAGE_CACHE);
>
> #ifdef CONFIG_SPARSEMEM_VMEMMAP
> -int __meminit vmemmap_populate(unsigned long vstart, unsigned long vend,
> - int node, struct vmem_altmap *altmap)
> +void __meminit vmemmap_set_pmd(pmd_t *pmd, void *p, int node,
> + unsigned long addr, unsigned long next)
> {
> unsigned long pte_base;
>
> @@ -2595,39 +2595,24 @@ int __meminit vmemmap_populate(unsigned long vstart, unsigned long vend,
>
> pte_base |= _PAGE_PMD_HUGE;
>
> - vstart = vstart & PMD_MASK;
> - vend = ALIGN(vend, PMD_SIZE);
It seems that this patch removes alignment of both start and end. Is
this a functional change in practice or are these always aligned for
some other reason?
> - for (; vstart < vend; vstart += PMD_SIZE) {
> - pgd_t *pgd = vmemmap_pgd_populate(vstart, node);
> - unsigned long pte;
> - p4d_t *p4d;
> - pud_t *pud;
> - pmd_t *pmd;
> -
> - if (!pgd)
> - return -ENOMEM;
> -
> - p4d = vmemmap_p4d_populate(pgd, vstart, node);
> - if (!p4d)
> - return -ENOMEM;
> -
> - pud = vmemmap_pud_populate(p4d, vstart, node);
> - if (!pud)
> - return -ENOMEM;
> + pmd_val(*pmd) = pte_base | __pa(p);
> +}
>
> - pmd = pmd_offset(pud, vstart);
> - pte = pmd_val(*pmd);
> - if (!(pte & _PAGE_VALID)) {
It is not the same thing, but is this equivalent to if
(pmd_none(pmdp_get(pmd))) at this point?
> - void *block = vmemmap_alloc_block(PMD_SIZE, node);
> +int __meminit vmemmap_check_pmd(pmd_t *pmdp, int node,
> + unsigned long addr, unsigned long next)
> +{
> + int large = pmd_leaf(*pmdp);
>
> - if (!block)
> - return -ENOMEM;
> + if (large)
> + vmemmap_verify((pte_t *)pmdp, node, addr, next);
>
> - pmd_val(*pmd) = pte_base | __pa(block);
> - }
> - }
> + return large;
> +}
>
> - return 0;
> +int __meminit vmemmap_populate(unsigned long vstart, unsigned long vend,
> + int node, struct vmem_altmap *altmap)
> +{
> + return vmemmap_populate_hugepages(vstart, vend, node, altmap);
> }
> #endif /* CONFIG_SPARSEMEM_VMEMMAP */
>
This change introduces using vmemmap_alloc_block_buf() instead of
vmemmap_alloc_block() seems to introduce two new behaviours that was not
in use for sparc64 before:
1) Using altmap_alloc_block_buf() for a non-null altmap, that was not
used before. Also the fallback to vmemmap_populate_basepages() passes
on altmap.
2) Trying sparse_buffer_alloc() before vmemmap_alloc_block(), which was
not done before.
Neither the commit message nor the cover letter touches upon this. Could
you elaborate here?
Given all the (at least seeming) functional changes could you share how
you tested this change?
Cheers,
Andreas
On Mon, Jan 26, 2026 at 10:50 PM Andreas Larsson <andreas@gaisler.com> wrote:
>
> On 2026-01-11 08:44, chengkaitao wrote:
> > From: Chengkaitao <chengkaitao@kylinos.cn>
> >
> > 1. In the SPARC architecture, reimplemented vmemmap_populate using
> > vmemmap_populate_hugepages.
> > 2. Allow the SPARC arch to fallback to vmemmap_populate_basepages(),
> > when vmemmap_alloc_block returns NULL.
>
> This patch seems to potentially make more functional changes than what
> the descriptions gives impression of.
>
> Given the amount of changes this seems to introduce, more on that below,
> I'd like to see more description on the changes and why they can be done
> than this.
>
> Nit: use active language, "reimplement", not "reimplemented".
>
>
> > Signed-off-by: Chengkaitao <chengkaitao@kylinos.cn>
> > Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> > ---
> > arch/sparc/mm/init_64.c | 47 ++++++++++++++---------------------------
> > 1 file changed, 16 insertions(+), 31 deletions(-)
> >
> > diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
> > index df9f7c444c39..858eaa6615ea 100644
> > --- a/arch/sparc/mm/init_64.c
> > +++ b/arch/sparc/mm/init_64.c
> > @@ -2581,8 +2581,8 @@ unsigned long _PAGE_CACHE __read_mostly;
> > EXPORT_SYMBOL(_PAGE_CACHE);
> >
> > #ifdef CONFIG_SPARSEMEM_VMEMMAP
> > -int __meminit vmemmap_populate(unsigned long vstart, unsigned long vend,
> > - int node, struct vmem_altmap *altmap)
> > +void __meminit vmemmap_set_pmd(pmd_t *pmd, void *p, int node,
> > + unsigned long addr, unsigned long next)
> > {
> > unsigned long pte_base;
> >
> > @@ -2595,39 +2595,24 @@ int __meminit vmemmap_populate(unsigned long vstart, unsigned long vend,
> >
> > pte_base |= _PAGE_PMD_HUGE;
> >
> > - vstart = vstart & PMD_MASK;
> > - vend = ALIGN(vend, PMD_SIZE);
>
> It seems that this patch removes alignment of both start and end. Is
> this a functional change in practice or are these always aligned for
> some other reason?
>
Whether vstart and vend are aligned with PMD_SIZE doesn't seem to
affect the behavior pattern or output of vmemmap_populate_hugepages.
The vmemmap_populate_hugepages function performs necessary alignment
processing internally, such as pmd_addr_end and pmd/pte_index?
> > - for (; vstart < vend; vstart += PMD_SIZE) {
> > - pgd_t *pgd = vmemmap_pgd_populate(vstart, node);
> > - unsigned long pte;
> > - p4d_t *p4d;
> > - pud_t *pud;
> > - pmd_t *pmd;
> > -
> > - if (!pgd)
> > - return -ENOMEM;
> > -
> > - p4d = vmemmap_p4d_populate(pgd, vstart, node);
> > - if (!p4d)
> > - return -ENOMEM;
> > -
> > - pud = vmemmap_pud_populate(p4d, vstart, node);
> > - if (!pud)
> > - return -ENOMEM;
> > + pmd_val(*pmd) = pte_base | __pa(p);
> > +}
> >
> > - pmd = pmd_offset(pud, vstart);
> > - pte = pmd_val(*pmd);
> > - if (!(pte & _PAGE_VALID)) {
>
> It is not the same thing, but is this equivalent to if
> (pmd_none(pmdp_get(pmd))) at this point?
>
For PMD entries, there shouldn't be cases where pmd_none and
_PAGE_VALID exhibit inconsistent behavior. I've observed that
pmd_none is widely used in the SPARC architecture.
> > - void *block = vmemmap_alloc_block(PMD_SIZE, node);
> > +int __meminit vmemmap_check_pmd(pmd_t *pmdp, int node,
> > + unsigned long addr, unsigned long next)
> > +{
> > + int large = pmd_leaf(*pmdp);
> >
> > - if (!block)
> > - return -ENOMEM;
> > + if (large)
> > + vmemmap_verify((pte_t *)pmdp, node, addr, next);
> >
> > - pmd_val(*pmd) = pte_base | __pa(block);
> > - }
> > - }
> > + return large;
> > +}
> >
> > - return 0;
> > +int __meminit vmemmap_populate(unsigned long vstart, unsigned long vend,
> > + int node, struct vmem_altmap *altmap)
> > +{
> > + return vmemmap_populate_hugepages(vstart, vend, node, altmap);
> > }
> > #endif /* CONFIG_SPARSEMEM_VMEMMAP */
> >
>
>
> This change introduces using vmemmap_alloc_block_buf() instead of
> vmemmap_alloc_block() seems to introduce two new behaviours that was not
> in use for sparc64 before:
>
> 1) Using altmap_alloc_block_buf() for a non-null altmap, that was not
> used before. Also the fallback to vmemmap_populate_basepages() passes
> on altmap.
If altmap validation isn't required, I can retain the original code
logic by setting altmap to NULL.
> 2) Trying sparse_buffer_alloc() before vmemmap_alloc_block(), which was
> not done before.
In SPARC, sparse_init() is called to initialize the sparsemap_buf.
If the SPARC architecture doesn't support using sparse_buffer_alloc,
we can remove the sparse_init() call path.
> Neither the commit message nor the cover letter touches upon this. Could
> you elaborate here?
>
> Given all the (at least seeming) functional changes could you share how
> you tested this change?
My original intention was to help architectures adopt more generic
kernel APIs to reduce maintenance costs. However, due to my lack of
physical SPARC devices, I couldn't perform comprehensive testing,
I've only verified compilation correctness based on code analysis.
I sincerely apologize for this limitation. If you have access to
physical SPARC hardware, could you kindly help with testing?
--
Cheers,
Chengkaitao
On Mon, 26 Jan 2026 15:50:34 +0100 Andreas Larsson <andreas@gaisler.com> wrote: > On 2026-01-11 08:44, chengkaitao wrote: > > From: Chengkaitao <chengkaitao@kylinos.cn> > > > > 1. In the SPARC architecture, reimplemented vmemmap_populate using > > vmemmap_populate_hugepages. > > 2. Allow the SPARC arch to fallback to vmemmap_populate_basepages(), > > when vmemmap_alloc_block returns NULL. > > This patch seems to potentially make more functional changes than what > the descriptions gives impression of. > > Given the amount of changes this seems to introduce, more on that below, > I'd like to see more description on the changes and why they can be done > than this. > > Nit: use active language, "reimplement", not "reimplemented". Thanks, I'll drop the v5 version of this patchset.
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