[LINUX] Support variable hypervisor_virt_start.

Introduce a new elfnote that specifies the lower boundary the kernel wants to tolerate for the hypervisor hole. Signed-off-by: Jan Beulich <jbeulich@novell.com>
2026-10-29 18:50:05 +01:00 · 2006-11-10 17:35:09 +00:00
1 parent 501330f105
commit b63bf4c482
@@ -9,7 +9,7 @@
 #include <asm/page.h>
 #include <asm/thread_info.h>
 #include <asm/asm-offsets.h>
-#include <xen/interface/arch-x86_32.h>
+#include <xen/interface/xen.h>
 #include <xen/interface/elfnote.h>

 /*
@@ -192,6 +192,7 @@ ENTRY(cpu_gdt_table)
 #endif /* !CONFIG_XEN_COMPAT_030002 */
 	ELFNOTE(Xen, XEN_ELFNOTE_ENTRY,          .long,  startup_32)
 	ELFNOTE(Xen, XEN_ELFNOTE_HYPERCALL_PAGE, .long,  hypercall_page)
+	ELFNOTE(Xen, XEN_ELFNOTE_HV_START_LOW,   .long,  HYPERVISOR_VIRT_START)
 	ELFNOTE(Xen, XEN_ELFNOTE_FEATURES,       .asciz, "writable_page_tables|writable_descriptor_tables|auto_translated_physmap|pae_pgdir_above_4gb|supervisor_mode_kernel")
 #ifdef CONFIG_X86_PAE
 	ELFNOTE(Xen, XEN_ELFNOTE_PAE_MODE,       .asciz, "yes")
@@ -282,12 +282,6 @@ static int spurious_fault(struct pt_regs *regs,
 	pmd_t *pmd;
 	pte_t *pte;

-#ifdef CONFIG_XEN
-	/* Faults in hypervisor area are never spurious. */
-	if (address >= HYPERVISOR_VIRT_START)
-		return 0;
-#endif
-
 	/* Reserved-bit violation or user access to kernel space? */
 	if (error_code & 0x0c)
 		return 0;
@@ -372,7 +366,7 @@ fastcall void __kprobes do_page_fault(struct pt_regs *regs,
 	if (unlikely(address >= TASK_SIZE)) { 
 #ifdef CONFIG_XEN
 		/* Faults in hypervisor area can never be patched up. */
-		if (address >= HYPERVISOR_VIRT_START)
+		if (address >= hypervisor_virt_start)
 			goto bad_area_nosemaphore;
 #endif
 		if (!(error_code & 5))
@@ -130,7 +130,7 @@ static void __init page_table_range_init (unsigned long start, unsigned long end
 		pud = pud_offset(pgd, vaddr);
 		pmd = pmd_offset(pud, vaddr);
 		for (; (pmd_idx < PTRS_PER_PMD) && (vaddr != end); pmd++, pmd_idx++) {
-			if (vaddr < HYPERVISOR_VIRT_START && pmd_none(*pmd)) 
+			if (vaddr < hypervisor_virt_start && pmd_none(*pmd))
 				one_page_table_init(pmd);

 			vaddr += PMD_SIZE;
@@ -187,7 +187,7 @@ static void __init kernel_physical_mapping_init(pgd_t *pgd_base)
 		pmd += pmd_idx;
 		for (; pmd_idx < PTRS_PER_PMD && pfn < max_low_pfn; pmd++, pmd_idx++) {
 			unsigned int address = pfn * PAGE_SIZE + PAGE_OFFSET;
-			if (address >= HYPERVISOR_VIRT_START)
+			if (address >= hypervisor_virt_start)
 				continue;

 			/* Map with big pages if possible, otherwise create normal page tables. */
@@ -410,7 +410,7 @@ static void __init pagetable_init (void)
 	 * created - mappings will be set by set_fixmap():
 	 */
 	vaddr = __fix_to_virt(__end_of_fixed_addresses - 1) & PMD_MASK;
-	page_table_range_init(vaddr, 0, pgd_base);
+	page_table_range_init(vaddr, hypervisor_virt_start, pgd_base);

 	permanent_kmaps_init(pgd_base);
 }
@@ -186,9 +186,16 @@ void set_pmd_pfn(unsigned long vaddr, unsigned long pfn, pgprot_t flags)
 }

 static int nr_fixmaps = 0;
+unsigned long hypervisor_virt_start = HYPERVISOR_VIRT_START;
 unsigned long __FIXADDR_TOP = (HYPERVISOR_VIRT_START - 2 * PAGE_SIZE);
 EXPORT_SYMBOL(__FIXADDR_TOP);

+void __init set_fixaddr_top()
+{
+	BUG_ON(nr_fixmaps > 0);
+	__FIXADDR_TOP = hypervisor_virt_start - 2 * PAGE_SIZE;
+}
+
 void __set_fixmap (enum fixed_addresses idx, maddr_t phys, pgprot_t flags)
 {
 	unsigned long address = __fix_to_virt(idx);
@@ -211,12 +218,6 @@ void __set_fixmap (enum fixed_addresses idx, maddr_t phys, pgprot_t flags)
 	nr_fixmaps++;
 }

-void set_fixaddr_top(unsigned long top)
-{
-	BUG_ON(nr_fixmaps > 0);
-	__FIXADDR_TOP = top - PAGE_SIZE;
-}
-
 pte_t *pte_alloc_one_kernel(struct mm_struct *mm, unsigned long address)
 {
 	pte_t *pte = (pte_t *)__get_free_page(GFP_KERNEL|__GFP_REPEAT|__GFP_ZERO);
@@ -98,7 +98,7 @@ enum fixed_addresses {
 extern void __set_fixmap(enum fixed_addresses idx,
 					maddr_t phys, pgprot_t flags);

-extern void set_fixaddr_top(unsigned long top);
+extern void set_fixaddr_top(void);

 #define set_fixmap(idx, phys) \
 		__set_fixmap(idx, phys, PAGE_KERNEL)
@@ -56,6 +56,10 @@

 extern shared_info_t *HYPERVISOR_shared_info;

+#ifdef CONFIG_X86_32
+extern unsigned long hypervisor_virt_start;
+#endif
+
 /* arch/xen/i386/kernel/setup.c */
 extern start_info_t *xen_start_info;
 #ifdef CONFIG_XEN_PRIVILEGED_GUEST
@@ -9,7 +9,6 @@

 #define PGDIR_SHIFT	22
 #define PTRS_PER_PGD	1024
-#define PTRS_PER_PGD_NO_HV	(HYPERVISOR_VIRT_START >> PGDIR_SHIFT)

 /*
 * the i386 is two-level, so we don't really have any
@@ -8,7 +8,6 @@
 */
 #define PGDIR_SHIFT	30
 #define PTRS_PER_PGD	4
-#define PTRS_PER_PGD_NO_HV 4

 /*
 * PMD_SHIFT determines the size of the area a middle-level
@@ -92,8 +92,10 @@ static void __init machine_specific_arch_setup(void)
 #endif

 	if (HYPERVISOR_xen_version(XENVER_platform_parameters,
-				   &pp) == 0)
-		set_fixaddr_top(pp.virt_start - PAGE_SIZE);
+				   &pp) == 0) {
+		hypervisor_virt_start = pp.virt_start;
+		set_fixaddr_top();
+	}

 	machine_to_phys_mapping = (unsigned long *)MACH2PHYS_VIRT_START;
 	machine_to_phys_nr_ents = MACH2PHYS_NR_ENTRIES;
@@ -138,6 +138,15 @@
 */
 #define XEN_ELFNOTE_BSD_SYMTAB    11

+/*
+ * The lowest address the hypervisor hole can begin at (numeric).
+ *
+ * This must not be set higher than HYPERVISOR_VIRT_START. Its presence
+ * also indicates to the hypervisor that the kernel can deal with the
+ * hole starting at a higher address.
+ */
+#define XEN_ELFNOTE_HV_START_LOW  12
+
 #endif /* __XEN_PUBLIC_ELFNOTE_H__ */

 /*