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authorRusty Russell <rusty@rustcorp.com.au>2008-02-04 23:50:03 -0500
committerRusty Russell <rusty@rustcorp.com.au>2008-02-04 23:50:03 +1100
commit6e5aa7efb27aec7e55b6463fa2c8db594c4226fa (patch)
tree060a955e711ac224136157a5410e88dcdab965af /Documentation
parentb3369c1fb410fddeb38a404316c861395f6d6ae8 (diff)
virtio: reset function
A reset function solves three problems: 1) It allows us to renegotiate features, eg. if we want to upgrade a guest driver without rebooting the guest. 2) It gives us a clean way of shutting down virtqueues: after a reset, we know that the buffers won't be used by the host, and 3) It helps the guest recover from messed-up drivers. So we remove the ->shutdown hook, and the only way we now remove feature bits is via reset. We leave it to the driver to do the reset before it deletes queues: the balloon driver, for example, needs to chat to the host in its remove function. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/lguest/lguest.c62
1 files changed, 52 insertions, 10 deletions
diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c
index 8ff2d8bc690a..0f23d67f958f 100644
--- a/Documentation/lguest/lguest.c
+++ b/Documentation/lguest/lguest.c
@@ -193,6 +193,13 @@ static void *_convert(struct iovec *iov, size_t size, size_t align,
#define le32_to_cpu(v32) (v32)
#define le64_to_cpu(v64) (v64)
+/* The device virtqueue descriptors are followed by feature bitmasks. */
+static u8 *get_feature_bits(struct device *dev)
+{
+ return (u8 *)(dev->desc + 1)
+ + dev->desc->num_vq * sizeof(struct lguest_vqconfig);
+}
+
/*L:100 The Launcher code itself takes us out into userspace, that scary place
* where pointers run wild and free! Unfortunately, like most userspace
* programs, it's quite boring (which is why everyone likes to hack on the
@@ -914,21 +921,58 @@ static void enable_fd(int fd, struct virtqueue *vq)
write(waker_fd, &vq->dev->fd, sizeof(vq->dev->fd));
}
+/* Resetting a device is fairly easy. */
+static void reset_device(struct device *dev)
+{
+ struct virtqueue *vq;
+
+ verbose("Resetting device %s\n", dev->name);
+ /* Clear the status. */
+ dev->desc->status = 0;
+
+ /* Clear any features they've acked. */
+ memset(get_feature_bits(dev) + dev->desc->feature_len, 0,
+ dev->desc->feature_len);
+
+ /* Zero out the virtqueues. */
+ for (vq = dev->vq; vq; vq = vq->next) {
+ memset(vq->vring.desc, 0,
+ vring_size(vq->config.num, getpagesize()));
+ vq->last_avail_idx = 0;
+ }
+}
+
/* This is the generic routine we call when the Guest uses LHCALL_NOTIFY. */
static void handle_output(int fd, unsigned long addr)
{
struct device *i;
struct virtqueue *vq;
- /* Check each virtqueue. */
+ /* Check each device and virtqueue. */
for (i = devices.dev; i; i = i->next) {
+ /* Notifications to device descriptors reset the device. */
+ if (from_guest_phys(addr) == i->desc) {
+ reset_device(i);
+ return;
+ }
+
+ /* Notifications to virtqueues mean output has occurred. */
for (vq = i->vq; vq; vq = vq->next) {
- if (vq->config.pfn == addr/getpagesize()) {
- verbose("Output to %s\n", vq->dev->name);
- if (vq->handle_output)
- vq->handle_output(fd, vq);
+ if (vq->config.pfn != addr/getpagesize())
+ continue;
+
+ /* Guest should acknowledge (and set features!) before
+ * using the device. */
+ if (i->desc->status == 0) {
+ warnx("%s gave early output", i->name);
return;
}
+
+ if (strcmp(vq->dev->name, "console") != 0)
+ verbose("Output to %s\n", vq->dev->name);
+ if (vq->handle_output)
+ vq->handle_output(fd, vq);
+ return;
}
}
@@ -1074,10 +1118,11 @@ static void add_virtqueue(struct device *dev, unsigned int num_descs,
vq->vring.used->flags = VRING_USED_F_NO_NOTIFY;
}
-/* The virtqueue descriptors are followed by feature bytes. */
+/* The first half of the feature bitmask is for us to advertise features. The
+ * second half if for the Guest to accept features. */
static void add_feature(struct device *dev, unsigned bit)
{
- u8 *features;
+ u8 *features = get_feature_bits(dev);
/* We can't extend the feature bits once we've added config bytes */
if (dev->desc->feature_len <= bit / CHAR_BIT) {
@@ -1085,9 +1130,6 @@ static void add_feature(struct device *dev, unsigned bit)
dev->desc->feature_len = (bit / CHAR_BIT) + 1;
}
- features = (u8 *)(dev->desc + 1)
- + dev->desc->num_vq * sizeof(struct lguest_vqconfig);
-
features[bit / CHAR_BIT] |= (1 << (bit % CHAR_BIT));
}