virtio: use LGUEST_VRING_ALIGN instead of relying on pagesize

This doesn't really matter, since lguest is i386 only at the moment,
but we could actually choose a different value.  (lguest doesn't have
a guarenteed ABI).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

3 files changed, 8 insertions, 4 deletions

diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c
index 804520633fcf..aa2574ca94c7 100644
--- a/Documentation/lguest/lguest.c
+++ b/Documentation/lguest/lguest.c
@@ -1030,7 +1030,7 @@ static void update_device_status(struct device *dev)
                 /* Zero out the virtqueues. */
                 for (vq = dev->vq; vq; vq = vq->next) {
                         memset(vq->vring.desc, 0,
-                               vring_size(vq->config.num, getpagesize()));
+                               vring_size(vq->config.num, LGUEST_VRING_ALIGN));
                         lg_last_avail(vq) = 0;
                 }
         } else if (dev->desc->status & VIRTIO_CONFIG_S_FAILED) {
@@ -1211,7 +1211,7 @@ static void add_virtqueue(struct device *dev, unsigned int num_descs,
         void *p;
 
         /* First we need some memory for this virtqueue. */
-        pages = (vring_size(num_descs, getpagesize()) + getpagesize() - 1)
+        pages = (vring_size(num_descs, LGUEST_VRING_ALIGN) + getpagesize() - 1)
                 / getpagesize();
         p = get_pages(pages);
 
@@ -1228,7 +1228,7 @@ static void add_virtqueue(struct device *dev, unsigned int num_descs,
         vq->config.pfn = to_guest_phys(p) / getpagesize();
 
         /* Initialize the vring. */
-        vring_init(&vq->vring, num_descs, p, getpagesize());
+        vring_init(&vq->vring, num_descs, p, LGUEST_VRING_ALIGN);
 
         /* Append virtqueue to this device's descriptor.  We use
          * device_config() to get the end of the device's current virtqueues;
diff --git a/drivers/lguest/lguest_device.c b/drivers/lguest/lguest_device.c
index a661bbdae3d6..f062dc55c573 100644
--- a/drivers/lguest/lguest_device.c
+++ b/drivers/lguest/lguest_device.c
@@ -250,7 +250,7 @@ static struct virtqueue *lg_find_vq(struct virtio_device *vdev,
         /* Figure out how many pages the ring will take, and map that memory */
         lvq->pages = lguest_map((unsigned long)lvq->config.pfn << PAGE_SHIFT,
                                 DIV_ROUND_UP(vring_size(lvq->config.num,
-                                                        PAGE_SIZE),
+                                                        LGUEST_VRING_ALIGN),
                                              PAGE_SIZE));
         if (!lvq->pages) {
                 err = -ENOMEM;
diff --git a/include/linux/lguest_launcher.h b/include/linux/lguest_launcher.h
index e7217dc58f39..bd0eba760522 100644
--- a/include/linux/lguest_launcher.h
+++ b/include/linux/lguest_launcher.h
@@ -59,4 +59,8 @@ enum lguest_req
         LHREQ_IRQ, /* + irq */
         LHREQ_BREAK, /* + on/off flag (on blocks until someone does off) */
 };
+
+/* The alignment to use between consumer and producer parts of vring.
+ * x86 pagesize for historical reasons. */
+#define LGUEST_VRING_ALIGN      4096
 #endif /* _LINUX_LGUEST_LAUNCHER */