MFC 307332,312086: Drop support for using mmap() with /dev/kmem.

307332:
Drop support for using mmap() with /dev/kmem.

Using the device pager with /dev/kmem is not stable since KVA mappings
are transient, but the device pager caches the PA associated with a
given offset forever.  Interestingly, mips' implementation of
memmap() already refused requests for /dev/kmem.

Note that kvm_read/kvm_write do not use mmap, but use read and write on
/dev/kmem, so this should not affect libkvm users.

312086:
Trim a few comments on platforms that did not implement mmap of /dev/kmem.

After r307332, no platforms implement mmap for /dev/kmem, so the lack of
it for these platforms is no longer unique.

1 files changed, 4 insertions, 5 deletions

diff --git a/sys/arm64/arm64/mem.c b/sys/arm64/arm64/mem.c
index 9044fb3..e0ea488 100644
--- a/sys/arm64/arm64/mem.c
+++ b/sys/arm64/arm64/mem.c
@@ -123,10 +123,9 @@ int
 memmmap(struct cdev *dev, vm_ooffset_t offset, vm_paddr_t *paddr,
     int prot __unused, vm_memattr_t *memattr __unused)
 {
-	if (dev2unit(dev) == CDEV_MINOR_MEM)
+	if (dev2unit(dev) == CDEV_MINOR_MEM) {
 		*paddr = offset;
-	else if (dev2unit(dev) == CDEV_MINOR_KMEM)
-		*paddr = vtophys(offset);
-	/* else panic! */
-	return (0);
+		return (0);
+	}
+	return (-1);
 }