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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 07:50:03 -0500
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,
193#define le32_to_cpu(v32) (v32) 193#define le32_to_cpu(v32) (v32)
194#define le64_to_cpu(v64) (v64) 194#define le64_to_cpu(v64) (v64)
195 195
196/* The device virtqueue descriptors are followed by feature bitmasks. */
197static u8 *get_feature_bits(struct device *dev)
198{
199 return (u8 *)(dev->desc + 1)
200 + dev->desc->num_vq * sizeof(struct lguest_vqconfig);
201}
202
196/*L:100 The Launcher code itself takes us out into userspace, that scary place 203/*L:100 The Launcher code itself takes us out into userspace, that scary place
197 * where pointers run wild and free! Unfortunately, like most userspace 204 * where pointers run wild and free! Unfortunately, like most userspace
198 * programs, it's quite boring (which is why everyone likes to hack on the 205 * 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)
914 write(waker_fd, &vq->dev->fd, sizeof(vq->dev->fd)); 921 write(waker_fd, &vq->dev->fd, sizeof(vq->dev->fd));
915} 922}
916 923
924/* Resetting a device is fairly easy. */
925static void reset_device(struct device *dev)
926{
927 struct virtqueue *vq;
928
929 verbose("Resetting device %s\n", dev->name);
930 /* Clear the status. */
931 dev->desc->status = 0;
932
933 /* Clear any features they've acked. */
934 memset(get_feature_bits(dev) + dev->desc->feature_len, 0,
935 dev->desc->feature_len);
936
937 /* Zero out the virtqueues. */
938 for (vq = dev->vq; vq; vq = vq->next) {
939 memset(vq->vring.desc, 0,
940 vring_size(vq->config.num, getpagesize()));
941 vq->last_avail_idx = 0;
942 }
943}
944
917/* This is the generic routine we call when the Guest uses LHCALL_NOTIFY. */ 945/* This is the generic routine we call when the Guest uses LHCALL_NOTIFY. */
918static void handle_output(int fd, unsigned long addr) 946static void handle_output(int fd, unsigned long addr)
919{ 947{
920 struct device *i; 948 struct device *i;
921 struct virtqueue *vq; 949 struct virtqueue *vq;
922 950
923 /* Check each virtqueue. */ 951 /* Check each device and virtqueue. */
924 for (i = devices.dev; i; i = i->next) { 952 for (i = devices.dev; i; i = i->next) {
953 /* Notifications to device descriptors reset the device. */
954 if (from_guest_phys(addr) == i->desc) {
955 reset_device(i);
956 return;
957 }
958
959 /* Notifications to virtqueues mean output has occurred. */
925 for (vq = i->vq; vq; vq = vq->next) { 960 for (vq = i->vq; vq; vq = vq->next) {
926 if (vq->config.pfn == addr/getpagesize()) { 961 if (vq->config.pfn != addr/getpagesize())
927 verbose("Output to %s\n", vq->dev->name); 962 continue;
928 if (vq->handle_output) 963
929 vq->handle_output(fd, vq); 964 /* Guest should acknowledge (and set features!) before
965 * using the device. */
966 if (i->desc->status == 0) {
967 warnx("%s gave early output", i->name);
930 return; 968 return;
931 } 969 }
970
971 if (strcmp(vq->dev->name, "console") != 0)
972 verbose("Output to %s\n", vq->dev->name);
973 if (vq->handle_output)
974 vq->handle_output(fd, vq);
975 return;
932 } 976 }
933 } 977 }
934 978
@@ -1074,10 +1118,11 @@ static void add_virtqueue(struct device *dev, unsigned int num_descs,
1074 vq->vring.used->flags = VRING_USED_F_NO_NOTIFY; 1118 vq->vring.used->flags = VRING_USED_F_NO_NOTIFY;
1075} 1119}
1076 1120
1077/* The virtqueue descriptors are followed by feature bytes. */ 1121/* The first half of the feature bitmask is for us to advertise features. The
1122 * second half if for the Guest to accept features. */
1078static void add_feature(struct device *dev, unsigned bit) 1123static void add_feature(struct device *dev, unsigned bit)
1079{ 1124{
1080 u8 *features; 1125 u8 *features = get_feature_bits(dev);
1081 1126
1082 /* We can't extend the feature bits once we've added config bytes */ 1127 /* We can't extend the feature bits once we've added config bytes */
1083 if (dev->desc->feature_len <= bit / CHAR_BIT) { 1128 if (dev->desc->feature_len <= bit / CHAR_BIT) {
@@ -1085,9 +1130,6 @@ static void add_feature(struct device *dev, unsigned bit)
1085 dev->desc->feature_len = (bit / CHAR_BIT) + 1; 1130 dev->desc->feature_len = (bit / CHAR_BIT) + 1;
1086 } 1131 }
1087 1132
1088 features = (u8 *)(dev->desc + 1)
1089 + dev->desc->num_vq * sizeof(struct lguest_vqconfig);
1090
1091 features[bit / CHAR_BIT] |= (1 << (bit % CHAR_BIT)); 1133 features[bit / CHAR_BIT] |= (1 << (bit % CHAR_BIT));
1092} 1134}
1093 1135