Create an identity mapping (V=P) super page for the low memory region on

boot.  Then, just switch to the kernel pmap when suspending instead of
allocating/freeing our own mapping every time.  This should solve a panic
of pmap_remove() being called with interrupts disabled.  Thanks to Alan
Cox for developing this patch.

Note: this means that ACPI requires super page (PG_PS) support in the CPU.
This has been present since the Pentium and first documented in the
Pentium Pro.  However, it may need to be revisited later.

Submitted by:	alc
MFC after:	1 month

2 files changed, 13 insertions, 11 deletions

diff --git a/sys/i386/acpica/acpi_wakeup.c b/sys/i386/acpica/acpi_wakeup.c
index 0b5a39e..cc5803d 100644
--- a/sys/i386/acpica/acpi_wakeup.c
+++ b/sys/i386/acpica/acpi_wakeup.c
@@ -192,11 +192,9 @@ acpi_sleep_machdep(struct acpi_softc *sc, int state)
 {
 	ACPI_STATUS		status;
 	struct pmap		*pm;
-	vm_page_t		page;
 	int			ret;
 	uint32_t		cr3;
 	u_long			ef;
-	struct proc		*p;
 
 	ret = 0;
 	if (sc->acpi_wakeaddr == 0)
@@ -206,10 +204,12 @@ acpi_sleep_machdep(struct acpi_softc *sc, int state)
 
 	ef = read_eflags();
 
-	/* Create Identity Mapping */
-	if ((p = curproc) == NULL)
-		p = &proc0;
-	pm = vmspace_pmap(p->p_vmspace);
+	/*
+	 * Temporarily switch to the kernel pmap because it provides an
+	 * identity mapping (setup at boot) for the low physical memory
+	 * region containing the wakeup code.
+	 */
+	pm = kernel_pmap;
 	cr3 = rcr3();
 #ifdef PAE
 	load_cr3(vtophys(pm->pm_pdpt));
@@ -217,10 +217,6 @@ acpi_sleep_machdep(struct acpi_softc *sc, int state)
 	load_cr3(vtophys(pm->pm_pdir));
 #endif
 
-	page = PHYS_TO_VM_PAGE(sc->acpi_wakephys);
-	pmap_enter(pm, sc->acpi_wakephys, page,
-		   VM_PROT_READ | VM_PROT_WRITE | VM_PROT_EXECUTE, 1);
-
 	ret_addr = 0;
 	ACPI_DISABLE_IRQS();
 	if (acpi_savecpu()) {
@@ -283,7 +279,6 @@ acpi_sleep_machdep(struct acpi_softc *sc, int state)
 	}
 
 out:
-	pmap_remove(pm, sc->acpi_wakephys, sc->acpi_wakephys + PAGE_SIZE);
 	load_cr3(cr3);
 	write_eflags(ef);
 
diff --git a/sys/i386/i386/pmap.c b/sys/i386/i386/pmap.c
index b2ab67d..18130fa 100644
--- a/sys/i386/i386/pmap.c
+++ b/sys/i386/i386/pmap.c
@@ -422,6 +422,13 @@ pmap_bootstrap(vm_paddr_t firstaddr, vm_paddr_t loadaddr)
 
 	/* Turn on PG_G on kernel page(s) */
 	pmap_set_pg();
+
+	/*
+	 * Create an identity mapping (virt == phys) for the low 1 MB
+	 * physical memory region that is used by the ACPI wakeup code.
+	 * This mapping must not have PG_G set. 
+	 */
+	kernel_pmap->pm_pdir[0] = PG_PS | PG_RW | PG_V;
 }
 
 /*