XEN/amd64 may initiate i/o over the pages not mapped by the direct

map.  Handle busdma bouncing and ata PIO accesses by using global
frame used by the current CPU locally for the duration of
pmap_quick_enter/remove_page().  A spin mutex protects the concurent
frame use and prevents thread migration.

Noted by:	royger
Reviewed by:	alc, jah, royger (previous version)
Sponsored by:	The FreeBSD Foundation

1 files changed, 24 insertions, 2 deletions

diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c
index 1e64fc8..41dea8b 100644
--- a/sys/amd64/amd64/pmap.c
+++ b/sys/amd64/amd64/pmap.c
@@ -390,6 +390,8 @@ static struct md_page *pv_table;
  */
 pt_entry_t *CMAP1 = 0;
 caddr_t CADDR1 = 0;
+static vm_offset_t qframe = 0;
+static struct mtx qframe_mtx;
 
 static int pmap_flags = PMAP_PDE_SUPERPAGE;	/* flags for x86 pmaps */
 
@@ -1031,7 +1033,7 @@ pmap_init(void)
 	struct pmap_preinit_mapping *ppim;
 	vm_page_t mpte;
 	vm_size_t s;
-	int i, pv_npg;
+	int error, i, pv_npg;
 
 	/*
 	 * Initialize the vm page array entries for the kernel pmap's
@@ -1112,6 +1114,12 @@ pmap_init(void)
 		printf("PPIM %u: PA=%#lx, VA=%#lx, size=%#lx, mode=%#x\n", i,
 		    ppim->pa, ppim->va, ppim->sz, ppim->mode);
 	}
+
+	mtx_init(&qframe_mtx, "qfrmlk", NULL, MTX_SPIN);
+	error = vmem_alloc(kernel_arena, PAGE_SIZE, M_BESTFIT | M_WAITOK,
+	    (vmem_addr_t *)&qframe);
+	if (error != 0)
+		panic("qframe allocation failed");
 }
 
 static SYSCTL_NODE(_vm_pmap, OID_AUTO, pde, CTLFLAG_RD, 0,
@@ -7019,13 +7027,27 @@ pmap_unmap_io_transient(vm_page_t page[], vm_offset_t vaddr[], int count,
 vm_offset_t
 pmap_quick_enter_page(vm_page_t m)
 {
+	vm_paddr_t paddr;
 
-	return (PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m)));
+	paddr = VM_PAGE_TO_PHYS(m);
+	if (paddr < dmaplimit)
+		return (PHYS_TO_DMAP(paddr));
+	mtx_lock_spin(&qframe_mtx);
+	KASSERT(*vtopte(qframe) == 0, ("qframe busy"));
+	pte_store(vtopte(qframe), paddr | X86_PG_RW | X86_PG_V | X86_PG_A |
+	    X86_PG_M | pmap_cache_bits(kernel_pmap, m->md.pat_mode, 0));
+	return (qframe);
 }
 
 void
 pmap_quick_remove_page(vm_offset_t addr)
 {
+
+	if (addr != qframe)
+		return;
+	pte_store(vtopte(qframe), 0);
+	invlpg(qframe);
+	mtx_unlock_spin(&qframe_mtx);
 }
 
 #include "opt_ddb.h"