Add two new pmap functions:

vm_offset_t pmap_quick_enter_page(vm_page_t m)
void pmap_quick_remove_page(vm_offset_t kva)

These will create and destroy a temporary, CPU-local KVA mapping of a specified page.

Guarantees:
--Will not sleep and will not fail.
--Safe to call under a non-sleepable lock or from an ithread

Restrictions:
--Not guaranteed to be safe to call from an interrupt filter or under a spin mutex on all platforms
--Current implementation does not guarantee more than one page of mapping space across all platforms. MI code should not make nested calls to pmap_quick_enter_page.
--MI code should not perform locking while holding onto a mapping created by pmap_quick_enter_page

The idea is to use this in busdma, for bounce buffer copies as well as virtually-indexed cache maintenance on mips and arm.

NOTE: the non-i386, non-amd64 implementations of these functions still need review and testing.

Reviewed by:	kib
Approved by:	kib (mentor)
Differential Revision:	http://reviews.freebsd.org/D3013

2 files changed, 51 insertions, 1 deletions

diff --git a/sys/i386/i386/pmap.c b/sys/i386/i386/pmap.c
index b02311e..efd44b3 100644
--- a/sys/i386/i386/pmap.c
+++ b/sys/i386/i386/pmap.c
@@ -512,6 +512,22 @@ pmap_bootstrap(vm_paddr_t firstaddr)
 	pmap_set_pg();
 }
 
+static void
+pmap_init_qpages(void)
+{
+	struct pcpu *pc;
+	int i;
+
+	CPU_FOREACH(i) {
+		pc = pcpu_find(i);
+		pc->pc_qmap_addr = kva_alloc(PAGE_SIZE);
+		if (pc->pc_qmap_addr == 0)
+			panic("pmap_init_qpages: unable to allocate KVA");
+	}
+}
+
+SYSINIT(qpages_init, SI_SUB_CPU, SI_ORDER_ANY, pmap_init_qpages, NULL);
+
 /*
  * Setup the PAT MSR.
  */
@@ -5400,6 +5416,39 @@ pmap_align_superpage(vm_object_t object, vm_ooffset_t offset,
 		*addr = ((*addr + PDRMASK) & ~PDRMASK) + superpage_offset;
 }
 
+vm_offset_t
+pmap_quick_enter_page(vm_page_t m)
+{
+	vm_offset_t qaddr;
+	pt_entry_t *pte;
+
+	critical_enter();
+	qaddr = PCPU_GET(qmap_addr);
+	pte = vtopte(qaddr);
+
+	KASSERT(*pte == 0, ("pmap_quick_enter_page: PTE busy"));
+	*pte = PG_V | PG_RW | VM_PAGE_TO_PHYS(m) | PG_A | PG_M |
+	    pmap_cache_bits(pmap_page_get_memattr(m), 0);
+	invlpg(qaddr);
+
+	return (qaddr);
+}
+
+void
+pmap_quick_remove_page(vm_offset_t addr)
+{
+	vm_offset_t qaddr;
+	pt_entry_t *pte;
+
+	qaddr = PCPU_GET(qmap_addr);
+	pte = vtopte(qaddr);
+
+	KASSERT(*pte != 0, ("pmap_quick_remove_page: PTE not in use"));
+	KASSERT(addr == qaddr, ("pmap_quick_remove_page: invalid address"));
+
+	*pte = 0;
+	critical_exit();
+}
 
 #if defined(PMAP_DEBUG)
 pmap_pid_dump(int pid)
diff --git a/sys/i386/include/pcpu.h b/sys/i386/include/pcpu.h
index 231f80f..cfd8d03 100644
--- a/sys/i386/include/pcpu.h
+++ b/sys/i386/include/pcpu.h
@@ -58,7 +58,8 @@
 	int	pc_private_tss;		/* Flag indicating private tss*/\
 	u_int	pc_cmci_mask;		/* MCx banks for CMCI */	\
 	u_int	pc_vcpu_id;		/* Xen vCPU ID */		\
-	char	__pad[233]
+	vm_offset_t pc_qmap_addr;	/* KVA for temporary mappings */\
+	char	__pad[229]
 
 #ifdef _KERNEL