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Subject[RESEND PATCH v4 5/5] lib/ioremap: Ensure break-before-make is used for huge p4d mappings
Date
Whilst no architectures actually enable support for huge p4d mappings
in the vmap area, the code that is implemented should be using
break-before-make, as we do for pud and pmd huge entries.

Cc: Chintan Pandya <cpandya@codeaurora.org>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Toshi Kani <toshi.kani@hpe.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
arch/arm64/mm/mmu.c | 5 +++++
arch/x86/mm/pgtable.c | 8 ++++++++
include/asm-generic/pgtable.h | 5 +++++
lib/ioremap.c | 27 +++++++++++++++++++++------
4 files changed, 39 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 786cfa6355be..cf9a26d3d7f5 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -1028,3 +1028,8 @@ int pud_free_pmd_page(pud_t *pudp, unsigned long addr)
pmd_free(NULL, table);
return 1;
}
+
+int p4d_free_pud_page(p4d_t *p4d, unsigned long addr)
+{
+ return 0; /* Don't attempt a block mapping */
+}
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index e95a7d6ac8f8..b0284eab14dc 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -794,6 +794,14 @@ int pmd_clear_huge(pmd_t *pmd)
return 0;
}

+/*
+ * Until we support 512GB pages, skip them in the vmap area.
+ */
+int p4d_free_pud_page(p4d_t *p4d, unsigned long addr)
+{
+ return 0;
+}
+
#ifdef CONFIG_X86_64
/**
* pud_free_pmd_page - Clear pud entry and free pmd page.
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 359fb935ded6..e0381a4ce7d4 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -1019,6 +1019,7 @@ int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot);
int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot);
int pud_clear_huge(pud_t *pud);
int pmd_clear_huge(pmd_t *pmd);
+int p4d_free_pud_page(p4d_t *p4d, unsigned long addr);
int pud_free_pmd_page(pud_t *pud, unsigned long addr);
int pmd_free_pte_page(pmd_t *pmd, unsigned long addr);
#else /* !CONFIG_HAVE_ARCH_HUGE_VMAP */
@@ -1046,6 +1047,10 @@ static inline int pmd_clear_huge(pmd_t *pmd)
{
return 0;
}
+static inline int p4d_free_pud_page(p4d_t *p4d, unsigned long addr)
+{
+ return 0;
+}
static inline int pud_free_pmd_page(pud_t *pud, unsigned long addr)
{
return 0;
diff --git a/lib/ioremap.c b/lib/ioremap.c
index 10d7c5485c39..063213685563 100644
--- a/lib/ioremap.c
+++ b/lib/ioremap.c
@@ -156,6 +156,25 @@ static inline int ioremap_pud_range(p4d_t *p4d, unsigned long addr,
return 0;
}

+static int ioremap_try_huge_p4d(p4d_t *p4d, unsigned long addr,
+ unsigned long end, phys_addr_t phys_addr,
+ pgprot_t prot)
+{
+ if (!ioremap_p4d_enabled())
+ return 0;
+
+ if ((end - addr) != P4D_SIZE)
+ return 0;
+
+ if (!IS_ALIGNED(phys_addr, P4D_SIZE))
+ return 0;
+
+ if (p4d_present(*p4d) && !p4d_free_pud_page(p4d, addr))
+ return 0;
+
+ return p4d_set_huge(p4d, phys_addr, prot);
+}
+
static inline int ioremap_p4d_range(pgd_t *pgd, unsigned long addr,
unsigned long end, phys_addr_t phys_addr, pgprot_t prot)
{
@@ -168,12 +187,8 @@ static inline int ioremap_p4d_range(pgd_t *pgd, unsigned long addr,
do {
next = p4d_addr_end(addr, end);

- if (ioremap_p4d_enabled() &&
- ((next - addr) == P4D_SIZE) &&
- IS_ALIGNED(phys_addr, P4D_SIZE)) {
- if (p4d_set_huge(p4d, phys_addr, prot))
- continue;
- }
+ if (ioremap_try_huge_p4d(p4d, addr, next, phys_addr, prot))
+ continue;

if (ioremap_pud_range(p4d, addr, next, phys_addr, prot))
return -ENOMEM;
--
2.1.4
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