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Date: Fri, 20 Mar 2020 17:08:31 +0000
From: Robin Murphy <robin.murphy@....com>
To: Anshuman Khandual <anshuman.khandual@....com>, linux-mm@...ck.org
Cc: Mark Rutland <mark.rutland@....com>,
Michal Hocko <mhocko@...e.com>, linux-ia64@...r.kernel.org,
David Hildenbrand <david@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Catalin Marinas <catalin.marinas@....com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
linux-riscv@...ts.infradead.org, Will Deacon <will@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
"Matthew Wilcox (Oracle)" <willy@...radead.org>,
Mike Rapoport <rppt@...ux.ibm.com>,
Ingo Molnar <mingo@...hat.com>,
Fenghua Yu <fenghua.yu@...el.com>,
Pavel Tatashin <pasha.tatashin@...een.com>,
Andy Lutomirski <luto@...nel.org>,
Paul Walmsley <paul.walmsley@...ive.com>,
Dan Williams <dan.j.williams@...el.com>,
linux-arm-kernel@...ts.infradead.org,
Tony Luck <tony.luck@...el.com>, linux-kernel@...r.kernel.org,
Palmer Dabbelt <palmer@...belt.com>,
Andrew Morton <akpm@...ux-foundation.org>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH V2 1/2] mm/sparsemem: Enable vmem_altmap support in
vmemmap_populate_basepages()
On 2020-03-04 2:10 pm, Anshuman Khandual wrote:
> vmemmap_populate_basepages() is used across platforms to allocate backing
> memory for vmemmap mapping. This is used as a standard default choice or
> as a fallback when intended huge pages allocation fails. This just creates
> entire vmemmap mapping with base pages (PAGE_SIZE).
>
> On arm64 platforms, vmemmap_populate_basepages() is called instead of the
> platform specific vmemmap_populate() when ARM64_SWAPPER_USES_SECTION_MAPS
> is not enabled as in case for ARM64_16K_PAGES and ARM64_64K_PAGES configs.
>
> At present vmemmap_populate_basepages() does not support allocating from
> driver defined struct vmem_altmap while trying to create vmemmap mapping
> for a device memory range. It prevents ARM64_16K_PAGES and ARM64_64K_PAGES
> configs on arm64 from supporting device memory with vmemap_altmap request.
>
> This enables vmem_altmap support in vmemmap_populate_basepages() unlocking
> device memory allocation for vmemap mapping on arm64 platforms with 16K or
> 64K base page configs.
>
> Each architecture should evaluate and decide on subscribing device memory
> based base page allocation through vmemmap_populate_basepages(). Hence lets
> keep it disabled on all archs in order to preserve the existing semantics.
> A subsequent patch enables it on arm64.
I guess buy-in for this change largely depends on whether any other
architectures are likely to want to share it. The existing altmap users
don't look like they would, so that's probably more a question for the
likes of S390 and RISC-V.
Failing that, simply decoupling arm64 from vmemmap_populate_basepages()
seems viable - I tried hacking up a quick proof-of-concept (attached at
the end) and it doesn't come out looking *too* disgusting.
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will@...nel.org>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Paul Walmsley <paul.walmsley@...ive.com>
> Cc: Palmer Dabbelt <palmer@...belt.com>
> Cc: Tony Luck <tony.luck@...el.com>
> Cc: Fenghua Yu <fenghua.yu@...el.com>
> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> Cc: Andy Lutomirski <luto@...nel.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: David Hildenbrand <david@...hat.com>
> Cc: Mike Rapoport <rppt@...ux.ibm.com>
> Cc: Michal Hocko <mhocko@...e.com>
> Cc: "Matthew Wilcox (Oracle)" <willy@...radead.org>
> Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Pavel Tatashin <pasha.tatashin@...een.com>
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: linux-ia64@...r.kernel.org
> Cc: linux-riscv@...ts.infradead.org
> Cc: x86@...nel.org
> Cc: linux-kernel@...r.kernel.org
>
> Acked-by: Will Deacon <will@...nel.org>
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> ---
> arch/arm64/mm/mmu.c | 2 +-
> arch/ia64/mm/discontig.c | 2 +-
> arch/riscv/mm/init.c | 2 +-
> arch/x86/mm/init_64.c | 6 +++---
> include/linux/mm.h | 5 +++--
> mm/sparse-vmemmap.c | 16 +++++++++++-----
> 6 files changed, 20 insertions(+), 13 deletions(-)
>
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 9b08f7c7e6f0..27cb95c471eb 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -1036,7 +1036,7 @@ static void free_empty_tables(unsigned long addr, unsigned long end,
> int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
> struct vmem_altmap *altmap)
> {
> - return vmemmap_populate_basepages(start, end, node);
> + return vmemmap_populate_basepages(start, end, node, NULL);
> }
> #else /* !ARM64_SWAPPER_USES_SECTION_MAPS */
> int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
> diff --git a/arch/ia64/mm/discontig.c b/arch/ia64/mm/discontig.c
> index 4f33f6e7e206..20409f3afea8 100644
> --- a/arch/ia64/mm/discontig.c
> +++ b/arch/ia64/mm/discontig.c
> @@ -656,7 +656,7 @@ void arch_refresh_nodedata(int update_node, pg_data_t *update_pgdat)
> int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
> struct vmem_altmap *altmap)
> {
> - return vmemmap_populate_basepages(start, end, node);
> + return vmemmap_populate_basepages(start, end, node, NULL);
> }
>
> void vmemmap_free(unsigned long start, unsigned long end,
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 965a8cf4829c..1d7451c91982 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -501,6 +501,6 @@ void __init paging_init(void)
> int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
> struct vmem_altmap *altmap)
> {
> - return vmemmap_populate_basepages(start, end, node);
> + return vmemmap_populate_basepages(start, end, node, NULL);
> }
> #endif
> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> index abbdecb75fad..3272fe0d844a 100644
> --- a/arch/x86/mm/init_64.c
> +++ b/arch/x86/mm/init_64.c
> @@ -1471,7 +1471,7 @@ static int __meminit vmemmap_populate_hugepages(unsigned long start,
> vmemmap_verify((pte_t *)pmd, node, addr, next);
> continue;
> }
> - if (vmemmap_populate_basepages(addr, next, node))
> + if (vmemmap_populate_basepages(addr, next, node, NULL))
> return -ENOMEM;
> }
> return 0;
> @@ -1483,7 +1483,7 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
> int err;
>
> if (end - start < PAGES_PER_SECTION * sizeof(struct page))
> - err = vmemmap_populate_basepages(start, end, node);
> + err = vmemmap_populate_basepages(start, end, node, NULL);
> else if (boot_cpu_has(X86_FEATURE_PSE))
> err = vmemmap_populate_hugepages(start, end, node, altmap);
> else if (altmap) {
> @@ -1491,7 +1491,7 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
> __func__);
> err = -ENOMEM;
> } else
> - err = vmemmap_populate_basepages(start, end, node);
> + err = vmemmap_populate_basepages(start, end, node, NULL);
> if (!err)
> sync_global_pgds(start, end - 1);
> return err;
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 52269e56c514..42f99c8d63c0 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2780,14 +2780,15 @@ pgd_t *vmemmap_pgd_populate(unsigned long addr, int node);
> p4d_t *vmemmap_p4d_populate(pgd_t *pgd, unsigned long addr, int node);
> pud_t *vmemmap_pud_populate(p4d_t *p4d, unsigned long addr, int node);
> pmd_t *vmemmap_pmd_populate(pud_t *pud, unsigned long addr, int node);
> -pte_t *vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, int node);
> +pte_t *vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, int node,
> + struct vmem_altmap *altmap);
> void *vmemmap_alloc_block(unsigned long size, int node);
> struct vmem_altmap;
> void *vmemmap_alloc_block_buf(unsigned long size, int node);
> void *altmap_alloc_block_buf(unsigned long size, struct vmem_altmap *altmap);
> void vmemmap_verify(pte_t *, int, unsigned long, unsigned long);
> int vmemmap_populate_basepages(unsigned long start, unsigned long end,
> - int node);
> + int node, struct vmem_altmap *altmap);
> int vmemmap_populate(unsigned long start, unsigned long end, int node,
> struct vmem_altmap *altmap);
> void vmemmap_populate_print_last(void);
> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
> index 200aef686722..a407abc9b46c 100644
> --- a/mm/sparse-vmemmap.c
> +++ b/mm/sparse-vmemmap.c
> @@ -140,12 +140,18 @@ void __meminit vmemmap_verify(pte_t *pte, int node,
> start, end - 1);
> }
>
> -pte_t * __meminit vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, int node)
> +pte_t * __meminit vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, int node,
> + struct vmem_altmap *altmap)
> {
> pte_t *pte = pte_offset_kernel(pmd, addr);
> if (pte_none(*pte)) {
> pte_t entry;
> - void *p = vmemmap_alloc_block_buf(PAGE_SIZE, node);
> + void *p;
> +
> + if (altmap)
> + p = altmap_alloc_block_buf(PAGE_SIZE, altmap);
> + else
> + p = vmemmap_alloc_block_buf(PAGE_SIZE, node);
This pattern ends up appearing a number of times by the end - if we do
go down the generic code route, might it be worth pushing it down into
vmmemmap_alloc_block_buf() itself to make it automatic? (possibly even
including the powerpc fallback behaviour too?)
Robin.
> if (!p)
> return NULL;
> entry = pfn_pte(__pa(p) >> PAGE_SHIFT, PAGE_KERNEL);
> @@ -213,8 +219,8 @@ pgd_t * __meminit vmemmap_pgd_populate(unsigned long addr, int node)
> return pgd;
> }
>
> -int __meminit vmemmap_populate_basepages(unsigned long start,
> - unsigned long end, int node)
> +int __meminit vmemmap_populate_basepages(unsigned long start, unsigned long end,
> + int node, struct vmem_altmap *altmap)
> {
> unsigned long addr = start;
> pgd_t *pgd;
> @@ -236,7 +242,7 @@ int __meminit vmemmap_populate_basepages(unsigned long start,
> pmd = vmemmap_pmd_populate(pud, addr, node);
> if (!pmd)
> return -ENOMEM;
> - pte = vmemmap_pte_populate(pmd, addr, node);
> + pte = vmemmap_pte_populate(pmd, addr, node, altmap);
> if (!pte)
> return -ENOMEM;
> vmemmap_verify(pte, node, addr, addr + PAGE_SIZE);
>
----->8-----
From: Robin Murphy <robin.murphy@....com>
Subject: [PATCH] arm64/mm: Consolidate vmemmap_populate()
Since we already have a custom vmemmap_populate() implementation, fold
the non-section-map case into that as well, so that we can easily add
altmap support for both cases without having to mess with core code.
Signed-off-by: Robin Murphy <robin.murphy@....com>
---
arch/arm64/mm/mmu.c | 34 +++++++++++++++++++++-------------
1 file changed, 21 insertions(+), 13 deletions(-)
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 128f70852bf3..e250fd414b2b 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -725,13 +725,6 @@ int kern_addr_valid(unsigned long addr)
return pfn_valid(pte_pfn(pte));
}
#ifdef CONFIG_SPARSEMEM_VMEMMAP
-#if !ARM64_SWAPPER_USES_SECTION_MAPS
-int __meminit vmemmap_populate(unsigned long start, unsigned long end,
int node,
- struct vmem_altmap *altmap)
-{
- return vmemmap_populate_basepages(start, end, node);
-}
-#else /* !ARM64_SWAPPER_USES_SECTION_MAPS */
int __meminit vmemmap_populate(unsigned long start, unsigned long end,
int node,
struct vmem_altmap *altmap)
{
@@ -740,6 +733,7 @@ int __meminit vmemmap_populate(unsigned long start,
unsigned long end, int node,
pgd_t *pgdp;
pud_t *pudp;
pmd_t *pmdp;
+ pte_t *ptep;
do {
next = pmd_addr_end(addr, end);
@@ -752,22 +746,36 @@ int __meminit vmemmap_populate(unsigned long
start, unsigned long end, int node,
if (!pudp)
return -ENOMEM;
+#if ARM64_SWAPPER_USES_SECTION_MAPS
pmdp = pmd_offset(pudp, addr);
if (pmd_none(READ_ONCE(*pmdp))) {
- void *p = NULL;
-
- p = vmemmap_alloc_block_buf(PMD_SIZE, node);
+ void *p = vmemmap_alloc_block_buf(PMD_SIZE, node);
if (!p)
return -ENOMEM;
pmd_set_huge(pmdp, __pa(p), __pgprot(PROT_SECT_NORMAL));
- } else
- vmemmap_verify((pte_t *)pmdp, node, addr, next);
+ continue;
+ }
+#else
+ pmdp = vmemmap_pmd_populate(pmdp, addr, node);
+ if (!pmdp)
+ return -ENOMEM;
+
+ ptep = pte_offset_kernel(pmdp, addr);
+ if (pte_none(READ_ONCE(*ptep))) {
+ void *p = vmemmap_alloc_block_buf(PAGE_SIZE, node);
+ if (!p)
+ return -ENOMEM;
+
+ set_pte(ptep, pfn_pte(__pa(p) >> PAGE_SHIFT, PAGE_KERNEL));
+ }
+#endif
+ vmemmap_verify((pte_t *)pmdp, node, addr, next);
} while (addr = next, addr != end);
return 0;
}
-#endif /* !ARM64_SWAPPER_USES_SECTION_MAPS */
+
void vmemmap_free(unsigned long start, unsigned long end,
struct vmem_altmap *altmap)
{
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