[Xen-devel] [PATCH 2/2] Linux support for hugepages as a Xen PV guest

[dcm@xxxxxxxx]

This patch adds support to Linux for hugepages as a Xen guest.  It is
against the linux-2.6.18-xen on xenbits.xensource.com.

It currently assumes that the guest memory is physically aligned and
contiguous.  Detection and avoidance of non-aligned memory will be
available in a future patch.

Signed-off-by: Dave McCracken <dave.mccracken@xxxxxxxxxx>

----


--- linux-2.6.18-xen//./fs/Kconfig      2008-07-17 09:54:14.000000000 -0500
+++ linux-hpage/./fs/Kconfig    2008-10-02 15:07:54.000000000 -0500
@@ -870,7 +870,7 @@ config TMPFS
 config HUGETLBFS
        bool "HugeTLB file system support"
        depends X86 || IA64 || PPC64 || SPARC64 || SUPERH || BROKEN
-       depends on !XEN
+#      depends on !XEN
        help
          hugetlbfs is a filesystem backing for HugeTLB pages, based on
          ramfs. For architectures that support it, say Y here and read
--- linux-2.6.18-xen//./include/asm-x86_64/mach-xen/asm/page.h  2008-07-17 
09:54:18.000000000 -0500
+++ linux-hpage/./include/asm-x86_64/mach-xen/asm/page.h        2008-10-02 
15:07:54.000000000 -0500
@@ -62,6 +62,8 @@
 #define HPAGE_MASK     (~(HPAGE_SIZE - 1))
 #define HUGETLB_PAGE_ORDER     (HPAGE_SHIFT - PAGE_SHIFT)
 
+#define ARCH_HAS_SETCLEAR_HUGE_PTE
+
 #ifdef __KERNEL__
 #ifndef __ASSEMBLY__
 
--- linux-2.6.18-xen//./include/asm-x86_64/mach-xen/asm/pgtable.h       
2008-08-14 10:06:46.000000000 -0500
+++ linux-hpage/./include/asm-x86_64/mach-xen/asm/pgtable.h     2008-10-02 
15:07:54.000000000 -0500
@@ -261,6 +261,12 @@ static inline unsigned long pud_bad(pud_
                set_pte((ptep), (pteval));                              \
 } while (0)
 
+static inline void set_huge_pte_at(struct mm_struct *mm, unsigned long addr, 
pte_t *ptep, pte_t pteval) {
+       if ((mm != current->mm && mm != &init_mm) ||
+           HYPERVISOR_update_va_mapping(addr, pteval, 0))
+               set_pmd((pmd_t *)ptep, (pmd_t){__pte_val(pteval)});
+}
+
 #define pte_none(x)    (!(x).pte)
 #define pte_present(x) ((x).pte & (_PAGE_PRESENT | _PAGE_PROTNONE))
 #define pte_clear(mm,addr,xp)  do { set_pte_at(mm, addr, xp, __pte(0)); } 
while (0)
@@ -296,6 +302,19 @@ static inline pte_t ptep_get_and_clear(s
        return pte;
 }
 
+static inline pte_t huge_ptep_get_and_clear(struct mm_struct *mm, unsigned 
long addr, pte_t *ptep)
+{
+       pte_t pte = *ptep;
+       if (!pte_none(pte)) {
+               if ((mm != &init_mm) ||
+                   HYPERVISOR_update_va_mapping(addr, __pte(0), 0)) {
+                       pte = *ptep;
+                       set_pmd((pmd_t *)ptep, __pmd(0));
+               }
+       }
+       return pte;
+}
+
 static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm, unsigned 
long addr, pte_t *ptep, int full)
 {
        if (full) {
--- linux-2.6.18-xen//./arch/x86_64/mm/pageattr-xen.c   2008-07-17 
09:54:10.000000000 -0500
+++ linux-hpage/./arch/x86_64/mm/pageattr-xen.c 2008-10-02 15:07:54.000000000 
-0500
@@ -62,6 +62,8 @@ static void _pin_lock(struct mm_struct *
 
                                        if (pmd_none(*pmd))
                                                continue;
+                                       if (pte_huge(*(pte_t *)pmd))
+                                               continue;
                                        ptl = pte_lockptr(0, pmd);
                                        if (lock)
                                                spin_lock(ptl);
--- linux-2.6.18-xen//./mm/hugetlb.c    2008-07-17 09:54:19.000000000 -0500
+++ linux-hpage/./mm/hugetlb.c  2008-10-02 15:07:54.000000000 -0500
@@ -294,12 +294,14 @@ static pte_t make_huge_pte(struct vm_are
                                int writable)
 {
        pte_t entry;
+       pgprot_t pgprot;
 
+       pgprot = __pgprot(pgprot_val(vma->vm_page_prot) | _PAGE_PRESENT);
        if (writable) {
                entry =
-                   pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot)));
+                   pte_mkwrite(pte_mkdirty(mk_pte(page, pgprot)));
        } else {
-               entry = pte_wrprotect(mk_pte(page, vma->vm_page_prot));
+               entry = pte_wrprotect(mk_pte(page, pgprot));
        }
        entry = pte_mkyoung(entry);
        entry = pte_mkhuge(entry);

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