[PATCH 1/5] Paravirt page alloc.patch

[Zachary Amsden]

The VMI backend uses explicit page type notification to track shadow
page tables.  The allocation of page table roots is especially tricky.
We want to clone the root for non-PAE mode while it is protected under
the pgd lock.

Signed-off-by: Zachary Amsden <zach@xxxxxxxxxx>

===================================================================
--- a/arch/i386/kernel/paravirt.c
+++ b/arch/i386/kernel/paravirt.c
@@ -545,6 +545,12 @@ struct paravirt_ops paravirt_ops = {
 	.flush_tlb_kernel = native_flush_tlb_global,
 	.flush_tlb_single = native_flush_tlb_single,
 
+	.alloc_pt = (void *)native_nop,
+	.alloc_pd = (void *)native_nop,
+	.alloc_pd_clone = (void *)native_nop,
+	.release_pt = (void *)native_nop,
+	.release_pd = (void *)native_nop,
+
 	.set_pte = native_set_pte,
 	.set_pte_at = native_set_pte_at,
 	.set_pmd = native_set_pmd,
===================================================================
--- a/arch/i386/mm/init.c
+++ b/arch/i386/mm/init.c
@@ -62,6 +62,7 @@ static pmd_t * __init one_md_table_init(
 		
 #ifdef CONFIG_X86_PAE
 	pmd_table = (pmd_t *) alloc_bootmem_low_pages(PAGE_SIZE);
+	paravirt_alloc_pd(__pa(pmd_table) >> PAGE_SHIFT);
 	set_pgd(pgd, __pgd(__pa(pmd_table) | _PAGE_PRESENT));
 	pud = pud_offset(pgd, 0);
 	if (pmd_table != pmd_offset(pud, 0)) 
@@ -82,6 +83,7 @@ static pte_t * __init one_page_table_ini
 {
 	if (pmd_none(*pmd)) {
 		pte_t *page_table = (pte_t *) alloc_bootmem_low_pages(PAGE_SIZE);
+		paravirt_alloc_pt(__pa(page_table) >> PAGE_SHIFT);
 		set_pmd(pmd, __pmd(__pa(page_table) | _PAGE_TABLE));
 		if (page_table != pte_offset_kernel(pmd, 0))
 			BUG();	
@@ -347,6 +349,8 @@ static void __init pagetable_init (void)
 	/* Init entries of the first-level page table to the zero page */
 	for (i = 0; i < PTRS_PER_PGD; i++)
 		set_pgd(pgd_base + i, __pgd(__pa(empty_zero_page) | _PAGE_PRESENT));
+#else
+	paravirt_alloc_pd(__pa(swapper_pg_dir) >> PAGE_SHIFT);
 #endif
 
 	/* Enable PSE if available */
===================================================================
--- a/arch/i386/mm/pageattr.c
+++ b/arch/i386/mm/pageattr.c
@@ -60,6 +60,7 @@ static struct page *split_large_page(uns
 	address = __pa(address);
 	addr = address & LARGE_PAGE_MASK; 
 	pbase = (pte_t *)page_address(base);
+	paravirt_alloc_pt(page_to_pfn(base));
 	for (i = 0; i < PTRS_PER_PTE; i++, addr += PAGE_SIZE) {
                set_pte(&pbase[i], pfn_pte(addr >> PAGE_SHIFT,
                                           addr == address ? prot : ref_prot));
@@ -166,6 +167,7 @@ __change_page_attr(struct page *page, pg
 	if (!PageReserved(kpte_page)) {
 		if (cpu_has_pse && (page_private(kpte_page) == 0)) {
 			ClearPagePrivate(kpte_page);
+			paravirt_release_pt(page_to_pfn(kpte_page));
 			list_add(&kpte_page->lru, &df_list);
 			revert_page(kpte_page, address);
 		}
===================================================================
--- a/arch/i386/mm/pgtable.c
+++ b/arch/i386/mm/pgtable.c
@@ -245,8 +245,14 @@ void pgd_ctor(void *pgd, kmem_cache_t *c
 	clone_pgd_range((pgd_t *)pgd + USER_PTRS_PER_PGD,
 			swapper_pg_dir + USER_PTRS_PER_PGD,
 			KERNEL_PGD_PTRS);
+
 	if (PTRS_PER_PMD > 1)
 		return;
+
+	/* must happen under lock */
+	paravirt_alloc_pd_clone(__pa(pgd) >> PAGE_SHIFT,
+			__pa(swapper_pg_dir) >> PAGE_SHIFT,
+			USER_PTRS_PER_PGD, PTRS_PER_PGD - USER_PTRS_PER_PGD);
 
 	pgd_list_add(pgd);
 	spin_unlock_irqrestore(&pgd_lock, flags);
@@ -257,6 +263,7 @@ void pgd_dtor(void *pgd, kmem_cache_t *c
 {
 	unsigned long flags; /* can be called from interrupt context */
 
+	paravirt_release_pd(__pa(pgd) >> PAGE_SHIFT);
 	spin_lock_irqsave(&pgd_lock, flags);
 	pgd_list_del(pgd);
 	spin_unlock_irqrestore(&pgd_lock, flags);
@@ -274,13 +281,18 @@ pgd_t *pgd_alloc(struct mm_struct *mm)
 		pmd_t *pmd = kmem_cache_alloc(pmd_cache, GFP_KERNEL);
 		if (!pmd)
 			goto out_oom;
+		paravirt_alloc_pd(__pa(pmd) >> PAGE_SHIFT);
 		set_pgd(&pgd[i], __pgd(1 + __pa(pmd)));
 	}
 	return pgd;
 
 out_oom:
-	for (i--; i >= 0; i--)
-		kmem_cache_free(pmd_cache, (void *)__va(pgd_val(pgd[i])-1));
+	for (i--; i >= 0; i--) {
+		pgd_t pgdent = pgd[i];
+		void* pmd = (void *)__va(pgd_val(pgdent)-1);
+		paravirt_release_pd(__pa(pmd) >> PAGE_SHIFT);
+		kmem_cache_free(pmd_cache, pmd);
+	}
 	kmem_cache_free(pgd_cache, pgd);
 	return NULL;
 }
@@ -291,8 +303,12 @@ void pgd_free(pgd_t *pgd)
 
 	/* in the PAE case user pgd entries are overwritten before usage */
 	if (PTRS_PER_PMD > 1)
-		for (i = 0; i < USER_PTRS_PER_PGD; ++i)
-			kmem_cache_free(pmd_cache, (void *)__va(pgd_val(pgd[i])-1));
+		for (i = 0; i < USER_PTRS_PER_PGD; ++i) {
+			pgd_t pgdent = pgd[i];
+			void* pmd = (void *)__va(pgd_val(pgdent)-1);
+			paravirt_release_pd(__pa(pmd) >> PAGE_SHIFT);
+			kmem_cache_free(pmd_cache, pmd);
+		}
 	/* in the non-PAE case, free_pgtables() clears user pgd entries */
 	kmem_cache_free(pgd_cache, pgd);
 }
===================================================================
--- a/include/asm-i386/paravirt.h
+++ b/include/asm-i386/paravirt.h
@@ -126,6 +126,12 @@ struct paravirt_ops
 	void (fastcall *flush_tlb_user)(void);
 	void (fastcall *flush_tlb_kernel)(void);
 	void (fastcall *flush_tlb_single)(u32 addr);
+
+	void (fastcall *alloc_pt)(u32 pfn);
+	void (fastcall *alloc_pd)(u32 pfn);
+	void (fastcall *alloc_pd_clone)(u32 pfn, u32 clonepfn, u32 start, u32 count);
+	void (fastcall *release_pt)(u32 pfn);
+	void (fastcall *release_pd)(u32 pfn);
 
 	void (fastcall *set_pte)(pte_t *ptep, pte_t pteval);
 	void (fastcall *set_pte_at)(struct mm_struct *mm, u32 addr, pte_t *ptep, pte_t pteval);
@@ -325,6 +331,14 @@ static __inline unsigned long apic_read(
 #define __flush_tlb_global() paravirt_ops.flush_tlb_kernel()
 #define __flush_tlb_single(addr) paravirt_ops.flush_tlb_single(addr)
 
+#define paravirt_alloc_pt(pfn) paravirt_ops.alloc_pt(pfn)
+#define paravirt_release_pt(pfn) paravirt_ops.release_pt(pfn)
+
+#define paravirt_alloc_pd(pfn) paravirt_ops.alloc_pd(pfn)
+#define paravirt_alloc_pd_clone(pfn, clonepfn, start, count) \
+	paravirt_ops.alloc_pd_clone(pfn, clonepfn, start, count)
+#define paravirt_release_pd(pfn) paravirt_ops.release_pd(pfn)
+
 static inline void set_pte(pte_t *ptep, pte_t pteval)
 {
 	paravirt_ops.set_pte(ptep, pteval);
===================================================================
--- a/include/asm-i386/pgalloc.h
+++ b/include/asm-i386/pgalloc.h
@@ -5,13 +5,31 @@
 #include <linux/threads.h>
 #include <linux/mm.h>		/* for struct page */
 
-#define pmd_populate_kernel(mm, pmd, pte) \
-		set_pmd(pmd, __pmd(_PAGE_TABLE + __pa(pte)))
+#ifdef CONFIG_PARAVIRT
+#include <asm/paravirt.h>
+#else
+#define paravirt_alloc_pt(pfn) do { } while (0)
+#define paravirt_alloc_pd(pfn) do { } while (0)
+#define paravirt_alloc_pd(pfn) do { } while (0)
+#define paravirt_alloc_pd_clone(pfn, clonepfn, start, count) do { } while (0)
+#define paravirt_release_pt(pfn) do { } while (0)
+#define paravirt_release_pd(pfn) do { } while (0)
+#endif
+
+#define pmd_populate_kernel(mm, pmd, pte)			\
+do {								\
+	paravirt_alloc_pt(__pa(pte) >> PAGE_SHIFT);		\
+	set_pmd(pmd, __pmd(_PAGE_TABLE + __pa(pte)));		\
+} while (0)
 
 #define pmd_populate(mm, pmd, pte) 				\
+do {								\
+	paravirt_alloc_pt(page_to_pfn(pte));			\
 	set_pmd(pmd, __pmd(_PAGE_TABLE +			\
 		((unsigned long long)page_to_pfn(pte) <<	\
-			(unsigned long long) PAGE_SHIFT)))
+			(unsigned long long) PAGE_SHIFT)));	\
+} while (0)
+
 /*
  * Allocate and free page tables.
  */
@@ -32,7 +50,11 @@ static inline void pte_free(struct page 
 }
 
 
-#define __pte_free_tlb(tlb,pte) tlb_remove_page((tlb),(pte))
+#define __pte_free_tlb(tlb,pte) 					\
+do {									\
+	paravirt_release_pt(page_to_pfn(pte));				\
+	tlb_remove_page((tlb),(pte));					\
+} while (0)
 
 #ifdef CONFIG_X86_PAE
 /*
-
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