[PATCH v3 1/2] x86/mm/ident_map: Add PUD level 1GB page support

[Xunlei Pang]

The current kernel_ident_mapping_init() creates the identity
mapping always using 2MB page(PMD level), this patch adds the
1GB page(PUD level) support.

The primary advantage would be better TLB coverage/performance,
because we'd utilize 1GB TLBs instead of 2MB ones.

It is also useful for machines with large number of memory to
save paging structure allocations(around 4MB/TB using 2MB page)
when setting identity mappings for all the memory, after using
1GB page it will consume only 8KB/TB.

Signed-off-by: Xunlei Pang 
---
 arch/x86/boot/compressed/pagetable.c |  2 +-
 arch/x86/include/asm/init.h  |  3 ++-
 arch/x86/kernel/machine_kexec_64.c   |  2 +-
 arch/x86/mm/ident_map.c  | 14 +-
 arch/x86/power/hibernate_64.c|  2 +-
 5 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/arch/x86/boot/compressed/pagetable.c 
b/arch/x86/boot/compressed/pagetable.c
index 56589d0..1d78f17 100644
--- a/arch/x86/boot/compressed/pagetable.c
+++ b/arch/x86/boot/compressed/pagetable.c
@@ -70,7 +70,7 @@ static void *alloc_pgt_page(void *context)
  * Due to relocation, pointers must be assigned at run time not build time.
  */
 static struct x86_mapping_info mapping_info = {
-   .pmd_flag   = __PAGE_KERNEL_LARGE_EXEC,
+   .page_flag   = __PAGE_KERNEL_LARGE_EXEC,
 };
 
 /* Locates and clears a region for a new top level page table. */
diff --git a/arch/x86/include/asm/init.h b/arch/x86/include/asm/init.h
index 737da62..474eb8c 100644
--- a/arch/x86/include/asm/init.h
+++ b/arch/x86/include/asm/init.h
@@ -4,8 +4,9 @@
 struct x86_mapping_info {
void *(*alloc_pgt_page)(void *); /* allocate buf for page table */
void *context;   /* context for alloc_pgt_page */
-   unsigned long pmd_flag;  /* page flag for PMD entry */
+   unsigned long page_flag; /* page flag for PMD or PUD entry */
unsigned long offset;/* ident mapping offset */
+   bool direct_gbpages; /* PUD level 1GB page support */
 };
 
 int kernel_ident_mapping_init(struct x86_mapping_info *info, pgd_t *pgd_page,
diff --git a/arch/x86/kernel/machine_kexec_64.c 
b/arch/x86/kernel/machine_kexec_64.c
index 085c3b3..1d4f2b0 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -113,7 +113,7 @@ static int init_pgtable(struct kimage *image, unsigned long 
start_pgtable)
struct x86_mapping_info info = {
.alloc_pgt_page = alloc_pgt_page,
.context= image,
-   .pmd_flag   = __PAGE_KERNEL_LARGE_EXEC,
+   .page_flag  = __PAGE_KERNEL_LARGE_EXEC,
};
unsigned long mstart, mend;
pgd_t *level4p;
diff --git a/arch/x86/mm/ident_map.c b/arch/x86/mm/ident_map.c
index 04210a2..adab159 100644
--- a/arch/x86/mm/ident_map.c
+++ b/arch/x86/mm/ident_map.c
@@ -13,7 +13,7 @@ static void ident_pmd_init(struct x86_mapping_info *info, 
pmd_t *pmd_page,
if (pmd_present(*pmd))
continue;
 
-   set_pmd(pmd, __pmd((addr - info->offset) | info->pmd_flag));
+   set_pmd(pmd, __pmd((addr - info->offset) | info->page_flag));
}
 }
 
@@ -30,6 +30,18 @@ static int ident_pud_init(struct x86_mapping_info *info, 
pud_t *pud_page,
if (next > end)
next = end;
 
+   if (info->direct_gbpages) {
+   pud_t pudval;
+
+   if (pud_present(*pud))
+   continue;
+
+   addr &= PUD_MASK;
+   pudval = __pud((addr - info->offset) | info->page_flag);
+   set_pud(pud, pudval);
+   continue;
+   }
+
if (pud_present(*pud)) {
pmd = pmd_offset(pud, 0);
ident_pmd_init(info, pmd, addr, next);
diff --git a/arch/x86/power/hibernate_64.c b/arch/x86/power/hibernate_64.c
index 6a61194..a6e21fe 100644
--- a/arch/x86/power/hibernate_64.c
+++ b/arch/x86/power/hibernate_64.c
@@ -104,7 +104,7 @@ static int set_up_temporary_mappings(void)
 {
struct x86_mapping_info info = {
.alloc_pgt_page = alloc_pgt_page,
-   .pmd_flag   = __PAGE_KERNEL_LARGE_EXEC,
+   .page_flag  = __PAGE_KERNEL_LARGE_EXEC,
.offset = __PAGE_OFFSET,
};
unsigned long mstart, mend;
-- 
1.8.3.1


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Re:

[H.A]

With profound love in my heart, I Kindly Oblige your interest to very important 
proposal.. It is Truly Divine and require your utmost attention..

S hlubokou láskou v mém srdci, Laskave jsem prinutit svuj zájem k návrhu .. Je 
velmi duležité, skutecne Divine a vyžadují vaši nejvyšší pozornost.

  Kontaktujte me prímo pres: helenarobert...@gmail.com pro úplné 
podrobnosti.complete.


HELINA .A ROBERTS

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