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authorJeremy Fitzhardinge <jeremy@goop.org>2007-05-02 19:27:13 +0200
committerAndi Kleen <andi@basil.nowhere.org>2007-05-02 19:27:13 +0200
commitb239fb2501117bf3aeb4dd6926edd855be92333d (patch)
tree62ac25204632ef0b14e3bd84580c722e69800cf7 /include
parent3dc494e86d1c93afd4c66385f270899dbfae483d (diff)
[PATCH] i386: PARAVIRT: Hooks to set up initial pagetable
This patch introduces paravirt_ops hooks to control how the kernel's initial pagetable is set up. In the case of a native boot, the very early bootstrap code creates a simple non-PAE pagetable to map the kernel and physical memory. When the VM subsystem is initialized, it creates a proper pagetable which respects the PAE mode, large pages, etc. When booting under a hypervisor, there are many possibilities for what paging environment the hypervisor establishes for the guest kernel, so the constructon of the kernel's pagetable depends on the hypervisor. In the case of Xen, the hypervisor boots the kernel with a fully constructed pagetable, which is already using PAE if necessary. Also, Xen requires particular care when constructing pagetables to make sure all pagetables are always mapped read-only. In order to make this easier, kernel's initial pagetable construction has been changed to only allocate and initialize a pagetable page if there's no page already present in the pagetable. This allows the Xen paravirt backend to make a copy of the hypervisor-provided pagetable, allowing the kernel to establish any more mappings it needs while keeping the existing ones. A slightly subtle point which is worth highlighting here is that Xen requires all kernel mappings to share the same pte_t pages between all pagetables, so that updating a kernel page's mapping in one pagetable is reflected in all other pagetables. This makes it possible to allocate a page and attach it to a pagetable without having to explicitly enumerate that page's mapping in all pagetables. And: +From: "Eric W. Biederman" <ebiederm@xmission.com> If we don't set the leaf page table entries it is quite possible that will inherit and incorrect page table entry from the initial boot page table setup in head.S. So we need to redo the effort here, so we pick up PSE, PGE and the like. Hypervisors like Xen require that their page tables be read-only, which is slightly incompatible with our low identity mappings, however I discussed this with Jeremy he has modified the Xen early set_pte function to avoid problems in this area. Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com> Signed-off-by: Andi Kleen <ak@suse.de> Acked-by: William Irwin <bill.irwin@oracle.com> Cc: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'include')
-rw-r--r--include/asm-i386/paravirt.h17
-rw-r--r--include/asm-i386/pgtable.h16
2 files changed, 32 insertions, 1 deletions
diff --git a/include/asm-i386/paravirt.h b/include/asm-i386/paravirt.h
index 0aacb13bb92..c49b44cdd8e 100644
--- a/include/asm-i386/paravirt.h
+++ b/include/asm-i386/paravirt.h
@@ -2,10 +2,11 @@
#define __ASM_PARAVIRT_H
/* Various instructions on x86 need to be replaced for
* para-virtualization: those hooks are defined here. */
+
+#ifdef CONFIG_PARAVIRT
#include <linux/stringify.h>
#include <asm/page.h>
-#ifdef CONFIG_PARAVIRT
/* These are the most performance critical ops, so we want to be able to patch
* callers */
#define PARAVIRT_IRQ_DISABLE 0
@@ -50,6 +51,9 @@ struct paravirt_ops
char *(*memory_setup)(void);
void (*init_IRQ)(void);
+ void (*pagetable_setup_start)(pgd_t *pgd_base);
+ void (*pagetable_setup_done)(pgd_t *pgd_base);
+
void (*banner)(void);
unsigned long (*get_wallclock)(void);
@@ -370,6 +374,17 @@ static inline void setup_secondary_clock(void)
}
#endif
+static inline void paravirt_pagetable_setup_start(pgd_t *base)
+{
+ if (paravirt_ops.pagetable_setup_start)
+ (*paravirt_ops.pagetable_setup_start)(base);
+}
+
+static inline void paravirt_pagetable_setup_done(pgd_t *base)
+{
+ if (paravirt_ops.pagetable_setup_done)
+ (*paravirt_ops.pagetable_setup_done)(base);
+}
#ifdef CONFIG_SMP
static inline void startup_ipi_hook(int phys_apicid, unsigned long start_eip,
diff --git a/include/asm-i386/pgtable.h b/include/asm-i386/pgtable.h
index 147f2553784..0790ad6ed44 100644
--- a/include/asm-i386/pgtable.h
+++ b/include/asm-i386/pgtable.h
@@ -514,6 +514,22 @@ do { \
* tables contain all the necessary information.
*/
#define update_mmu_cache(vma,address,pte) do { } while (0)
+
+void native_pagetable_setup_start(pgd_t *base);
+void native_pagetable_setup_done(pgd_t *base);
+
+#ifndef CONFIG_PARAVIRT
+static inline void paravirt_pagetable_setup_start(pgd_t *base)
+{
+ native_pagetable_setup_start(base);
+}
+
+static inline void paravirt_pagetable_setup_done(pgd_t *base)
+{
+ native_pagetable_setup_done(base);
+}
+#endif /* !CONFIG_PARAVIRT */
+
#endif /* !__ASSEMBLY__ */
#ifdef CONFIG_FLATMEM