lguest: map_switcher_in_guest() per-vcpu

The switcher needs to be mapped per-vcpu, because different vcpus
will potentially have different page tables (they don't have to,
because threads will share the same).

So our first step is the make the function receive a vcpu struct
Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

drivers/lguest/lg.h

@@ -168,7 +168,7 @@ void guest_pagetable_clear_all(struct lguest *lg);
 void guest_pagetable_flush_user(struct lguest *lg);
 void guest_set_pte(struct lguest *lg, unsigned long gpgdir,
 		   unsigned long vaddr, pte_t val);
-void map_switcher_in_guest(struct lguest *lg, struct lguest_pages *pages);
+void map_switcher_in_guest(struct lg_cpu *cpu, struct lguest_pages *pages);
 int demand_page(struct lguest *info, unsigned long cr2, int errcode);
 void pin_page(struct lguest *lg, unsigned long vaddr);
 unsigned long guest_pa(struct lguest *lg, unsigned long vaddr);

drivers/lguest/page_tables.c

@@ -634,8 +634,9 @@ void free_guest_pagetable(struct lguest *lg)
  * Guest (and not the pages for other CPUs).  We have the appropriate PTE pages
  * for each CPU already set up, we just need to hook them in now we know which
  * Guest is about to run on this CPU. */
-void map_switcher_in_guest(struct lguest *lg, struct lguest_pages *pages)
+void map_switcher_in_guest(struct lg_cpu *cpu, struct lguest_pages *pages)
 {
+	struct lguest *lg = cpu->lg;
 	pte_t *switcher_pte_page = __get_cpu_var(switcher_pte_pages);
 	pgd_t switcher_pgd;
 	pte_t regs_pte;

drivers/lguest/x86/core.c

@@ -91,7 +91,7 @@ static void copy_in_guest_info(struct lg_cpu *cpu, struct lguest_pages *pages)
 	pages->state.host_cr3 = __pa(current->mm->pgd);
 	/* Set up the Guest's page tables to see this CPU's pages (and no
 	 * other CPU's pages). */
-	map_switcher_in_guest(lg, pages);
+	map_switcher_in_guest(cpu, pages);
 	/* Set up the two "TSS" members which tell the CPU what stack to use
 	 * for traps which do directly into the Guest (ie. traps at privilege
 	 * level 1). */