From 9f7105d6ac9eb99fa031682b24570596334d68c9 Mon Sep 17 00:00:00 2001
From: "kfraser@localhost.localdomain" <kfraser@localhost.localdomain>
Date: Fri, 12 Jan 2007 10:28:54 +0000
Subject: [PATCH] linux/i386: allow CONFIG_HIGHPTE on i386

While, as discussed, the performance impact of this option is
certainly higher than on native Linux, the option should not be
entirely disallowed if people want to sacrifice performance for less
lowmem pressure.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
---
 linux-2.6-xen-sparse/arch/i386/Kconfig        |  2 +-
 .../arch/i386/mm/highmem-xen.c                |  1 +
 .../arch/i386/mm/pgtable-xen.c                | 28 +++++++++++++++----
 .../include/asm-i386/mach-xen/asm/pgalloc.h   |  2 +-
 4 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/linux-2.6-xen-sparse/arch/i386/Kconfig b/linux-2.6-xen-sparse/arch/i386/Kconfig
index 8c712269d0..4c0d2f8c80 100644
--- a/linux-2.6-xen-sparse/arch/i386/Kconfig
+++ b/linux-2.6-xen-sparse/arch/i386/Kconfig
@@ -594,7 +594,7 @@ config HAVE_ARCH_EARLY_PFN_TO_NID
 
 config HIGHPTE
 	bool "Allocate 3rd-level pagetables from highmem"
-	depends on (HIGHMEM4G || HIGHMEM64G) && !X86_XEN
+	depends on HIGHMEM4G || HIGHMEM64G
 	help
 	  The VM uses one page table entry for each page of physical memory.
 	  For systems with a lot of RAM, this can be wasteful of precious
diff --git a/linux-2.6-xen-sparse/arch/i386/mm/highmem-xen.c b/linux-2.6-xen-sparse/arch/i386/mm/highmem-xen.c
index 23f0e1b2e9..ee7deae2a7 100644
--- a/linux-2.6-xen-sparse/arch/i386/mm/highmem-xen.c
+++ b/linux-2.6-xen-sparse/arch/i386/mm/highmem-xen.c
@@ -129,5 +129,6 @@ struct page *kmap_atomic_to_page(void *ptr)
 EXPORT_SYMBOL(kmap);
 EXPORT_SYMBOL(kunmap);
 EXPORT_SYMBOL(kmap_atomic);
+EXPORT_SYMBOL(kmap_atomic_pte);
 EXPORT_SYMBOL(kunmap_atomic);
 EXPORT_SYMBOL(kmap_atomic_to_page);
diff --git a/linux-2.6-xen-sparse/arch/i386/mm/pgtable-xen.c b/linux-2.6-xen-sparse/arch/i386/mm/pgtable-xen.c
index 0ff01f52f8..8f2239b427 100644
--- a/linux-2.6-xen-sparse/arch/i386/mm/pgtable-xen.c
+++ b/linux-2.6-xen-sparse/arch/i386/mm/pgtable-xen.c
@@ -238,23 +238,41 @@ struct page *pte_alloc_one(struct mm_struct *mm, unsigned long address)
 
 #ifdef CONFIG_HIGHPTE
 	pte = alloc_pages(GFP_KERNEL|__GFP_HIGHMEM|__GFP_REPEAT|__GFP_ZERO, 0);
+	if (pte && PageHighMem(pte)) {
+		struct mmuext_op op;
+
+		kmap_flush_unused();
+		op.cmd = MMUEXT_PIN_L1_TABLE;
+		op.arg1.mfn = pfn_to_mfn(page_to_pfn(pte));
+		BUG_ON(HYPERVISOR_mmuext_op(&op, 1, NULL, DOMID_SELF) < 0);
+	}
 #else
 	pte = alloc_pages(GFP_KERNEL|__GFP_REPEAT|__GFP_ZERO, 0);
+#endif
 	if (pte) {
 		SetPageForeign(pte, pte_free);
 		set_page_count(pte, 1);
 	}
-#endif
 	return pte;
 }
 
 void pte_free(struct page *pte)
 {
-	unsigned long va = (unsigned long)__va(page_to_pfn(pte)<<PAGE_SHIFT);
+	unsigned long pfn = page_to_pfn(pte);
 
-	if (!pte_write(*virt_to_ptep(va)))
-		BUG_ON(HYPERVISOR_update_va_mapping(
-			va, pfn_pte(page_to_pfn(pte), PAGE_KERNEL), 0));
+	if (!PageHighMem(pte)) {
+		unsigned long va = (unsigned long)__va(pfn << PAGE_SHIFT);
+
+		if (!pte_write(*virt_to_ptep(va)))
+			BUG_ON(HYPERVISOR_update_va_mapping(
+			       va, pfn_pte(pfn, PAGE_KERNEL), 0));
+	} else {
+		struct mmuext_op op;
+
+		op.cmd = MMUEXT_UNPIN_TABLE;
+		op.arg1.mfn = pfn_to_mfn(pfn);
+		BUG_ON(HYPERVISOR_mmuext_op(&op, 1, NULL, DOMID_SELF) < 0);
+	}
 
 	ClearPageForeign(pte);
 	set_page_count(pte, 1);
diff --git a/linux-2.6-xen-sparse/include/asm-i386/mach-xen/asm/pgalloc.h b/linux-2.6-xen-sparse/include/asm-i386/mach-xen/asm/pgalloc.h
index 95f8d9dadb..39252d1ad8 100644
--- a/linux-2.6-xen-sparse/include/asm-i386/mach-xen/asm/pgalloc.h
+++ b/linux-2.6-xen-sparse/include/asm-i386/mach-xen/asm/pgalloc.h
@@ -42,7 +42,7 @@ extern struct page *pte_alloc_one(struct mm_struct *, unsigned long);
 static inline void pte_free_kernel(pte_t *pte)
 {
 	free_page((unsigned long)pte);
-	make_page_writable(pte, XENFEAT_writable_page_tables);
+	make_lowmem_page_writable(pte, XENFEAT_writable_page_tables);
 }
 
 extern void pte_free(struct page *pte);
-- 
2.30.2