Anthony Liguori points out that three different transports use the virtio code, but each one keeps its own counter to set the virtio_device's index field. In theory (though not in current practice) this means that names could be duplicated, and that risk grows as more transports are created. So we move the selection of the unique virtio_device.index into the common code in virtio.c, which has the side-benefit of removing duplicate code. The only complexity is that lguest and S/390 use the index to uniquely identify the device in case of catastrophic failure before register_virtio_device() is called: now we use the offset within the descriptor page as a unique identifier for the printks. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Carsten Otte <cotte@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Chris Lalancette <clalance@redhat.com> Cc: Anthony Liguori <anthony@codemonkey.ws>
417 lines
13 KiB
C
417 lines
13 KiB
C
/*P:050 Lguest guests use a very simple method to describe devices. It's a
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* series of device descriptors contained just above the top of normal Guest
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* memory.
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*
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* We use the standard "virtio" device infrastructure, which provides us with a
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* console, a network and a block driver. Each one expects some configuration
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* information and a "virtqueue" or two to send and receive data. :*/
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#include <linux/init.h>
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#include <linux/bootmem.h>
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#include <linux/lguest_launcher.h>
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#include <linux/virtio.h>
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#include <linux/virtio_config.h>
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#include <linux/interrupt.h>
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#include <linux/virtio_ring.h>
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#include <linux/err.h>
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#include <asm/io.h>
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#include <asm/paravirt.h>
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#include <asm/lguest_hcall.h>
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/* The pointer to our (page) of device descriptions. */
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static void *lguest_devices;
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/* For Guests, device memory can be used as normal memory, so we cast away the
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* __iomem to quieten sparse. */
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static inline void *lguest_map(unsigned long phys_addr, unsigned long pages)
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{
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return (__force void *)ioremap_cache(phys_addr, PAGE_SIZE*pages);
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}
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static inline void lguest_unmap(void *addr)
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{
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iounmap((__force void __iomem *)addr);
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}
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/*D:100 Each lguest device is just a virtio device plus a pointer to its entry
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* in the lguest_devices page. */
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struct lguest_device {
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struct virtio_device vdev;
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/* The entry in the lguest_devices page for this device. */
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struct lguest_device_desc *desc;
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};
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/* Since the virtio infrastructure hands us a pointer to the virtio_device all
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* the time, it helps to have a curt macro to get a pointer to the struct
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* lguest_device it's enclosed in. */
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#define to_lgdev(vd) container_of(vd, struct lguest_device, vdev)
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/*D:130
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* Device configurations
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*
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* The configuration information for a device consists of one or more
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* virtqueues, a feature bitmap, and some configuration bytes. The
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* configuration bytes don't really matter to us: the Launcher sets them up, and
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* the driver will look at them during setup.
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*
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* A convenient routine to return the device's virtqueue config array:
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* immediately after the descriptor. */
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static struct lguest_vqconfig *lg_vq(const struct lguest_device_desc *desc)
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{
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return (void *)(desc + 1);
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}
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/* The features come immediately after the virtqueues. */
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static u8 *lg_features(const struct lguest_device_desc *desc)
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{
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return (void *)(lg_vq(desc) + desc->num_vq);
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}
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/* The config space comes after the two feature bitmasks. */
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static u8 *lg_config(const struct lguest_device_desc *desc)
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{
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return lg_features(desc) + desc->feature_len * 2;
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}
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/* The total size of the config page used by this device (incl. desc) */
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static unsigned desc_size(const struct lguest_device_desc *desc)
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{
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return sizeof(*desc)
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+ desc->num_vq * sizeof(struct lguest_vqconfig)
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+ desc->feature_len * 2
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+ desc->config_len;
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}
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/* This gets the device's feature bits. */
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static u32 lg_get_features(struct virtio_device *vdev)
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{
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unsigned int i;
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u32 features = 0;
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struct lguest_device_desc *desc = to_lgdev(vdev)->desc;
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u8 *in_features = lg_features(desc);
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/* We do this the slow but generic way. */
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for (i = 0; i < min(desc->feature_len * 8, 32); i++)
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if (in_features[i / 8] & (1 << (i % 8)))
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features |= (1 << i);
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return features;
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}
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static void lg_set_features(struct virtio_device *vdev, u32 features)
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{
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unsigned int i;
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struct lguest_device_desc *desc = to_lgdev(vdev)->desc;
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/* Second half of bitmap is features we accept. */
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u8 *out_features = lg_features(desc) + desc->feature_len;
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memset(out_features, 0, desc->feature_len);
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for (i = 0; i < min(desc->feature_len * 8, 32); i++) {
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if (features & (1 << i))
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out_features[i / 8] |= (1 << (i % 8));
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}
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}
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/* Once they've found a field, getting a copy of it is easy. */
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static void lg_get(struct virtio_device *vdev, unsigned int offset,
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void *buf, unsigned len)
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{
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struct lguest_device_desc *desc = to_lgdev(vdev)->desc;
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/* Check they didn't ask for more than the length of the config! */
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BUG_ON(offset + len > desc->config_len);
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memcpy(buf, lg_config(desc) + offset, len);
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}
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/* Setting the contents is also trivial. */
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static void lg_set(struct virtio_device *vdev, unsigned int offset,
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const void *buf, unsigned len)
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{
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struct lguest_device_desc *desc = to_lgdev(vdev)->desc;
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/* Check they didn't ask for more than the length of the config! */
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BUG_ON(offset + len > desc->config_len);
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memcpy(lg_config(desc) + offset, buf, len);
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}
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/* The operations to get and set the status word just access the status field
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* of the device descriptor. */
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static u8 lg_get_status(struct virtio_device *vdev)
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{
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return to_lgdev(vdev)->desc->status;
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}
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/* To notify on status updates, we (ab)use the NOTIFY hypercall, with the
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* descriptor address of the device. A zero status means "reset". */
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static void set_status(struct virtio_device *vdev, u8 status)
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{
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unsigned long offset = (void *)to_lgdev(vdev)->desc - lguest_devices;
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/* We set the status. */
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to_lgdev(vdev)->desc->status = status;
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hcall(LHCALL_NOTIFY, (max_pfn<<PAGE_SHIFT) + offset, 0, 0);
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}
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static void lg_set_status(struct virtio_device *vdev, u8 status)
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{
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BUG_ON(!status);
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set_status(vdev, status);
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}
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static void lg_reset(struct virtio_device *vdev)
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{
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set_status(vdev, 0);
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}
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/*
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* Virtqueues
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*
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* The other piece of infrastructure virtio needs is a "virtqueue": a way of
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* the Guest device registering buffers for the other side to read from or
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* write into (ie. send and receive buffers). Each device can have multiple
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* virtqueues: for example the console driver uses one queue for sending and
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* another for receiving.
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*
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* Fortunately for us, a very fast shared-memory-plus-descriptors virtqueue
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* already exists in virtio_ring.c. We just need to connect it up.
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*
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* We start with the information we need to keep about each virtqueue.
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*/
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/*D:140 This is the information we remember about each virtqueue. */
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struct lguest_vq_info
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{
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/* A copy of the information contained in the device config. */
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struct lguest_vqconfig config;
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/* The address where we mapped the virtio ring, so we can unmap it. */
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void *pages;
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};
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/* When the virtio_ring code wants to prod the Host, it calls us here and we
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* make a hypercall. We hand the physical address of the virtqueue so the Host
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* knows which virtqueue we're talking about. */
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static void lg_notify(struct virtqueue *vq)
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{
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/* We store our virtqueue information in the "priv" pointer of the
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* virtqueue structure. */
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struct lguest_vq_info *lvq = vq->priv;
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hcall(LHCALL_NOTIFY, lvq->config.pfn << PAGE_SHIFT, 0, 0);
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}
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/* This routine finds the first virtqueue described in the configuration of
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* this device and sets it up.
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*
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* This is kind of an ugly duckling. It'd be nicer to have a standard
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* representation of a virtqueue in the configuration space, but it seems that
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* everyone wants to do it differently. The KVM coders want the Guest to
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* allocate its own pages and tell the Host where they are, but for lguest it's
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* simpler for the Host to simply tell us where the pages are.
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*
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* So we provide drivers with a "find the Nth virtqueue and set it up"
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* function. */
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static struct virtqueue *lg_find_vq(struct virtio_device *vdev,
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unsigned index,
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void (*callback)(struct virtqueue *vq))
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{
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struct lguest_device *ldev = to_lgdev(vdev);
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struct lguest_vq_info *lvq;
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struct virtqueue *vq;
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int err;
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/* We must have this many virtqueues. */
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if (index >= ldev->desc->num_vq)
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return ERR_PTR(-ENOENT);
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lvq = kmalloc(sizeof(*lvq), GFP_KERNEL);
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if (!lvq)
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return ERR_PTR(-ENOMEM);
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/* Make a copy of the "struct lguest_vqconfig" entry, which sits after
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* the descriptor. We need a copy because the config space might not
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* be aligned correctly. */
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memcpy(&lvq->config, lg_vq(ldev->desc)+index, sizeof(lvq->config));
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printk("Mapping virtqueue %i addr %lx\n", index,
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(unsigned long)lvq->config.pfn << PAGE_SHIFT);
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/* Figure out how many pages the ring will take, and map that memory */
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lvq->pages = lguest_map((unsigned long)lvq->config.pfn << PAGE_SHIFT,
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DIV_ROUND_UP(vring_size(lvq->config.num,
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PAGE_SIZE),
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PAGE_SIZE));
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if (!lvq->pages) {
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err = -ENOMEM;
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goto free_lvq;
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}
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/* OK, tell virtio_ring.c to set up a virtqueue now we know its size
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* and we've got a pointer to its pages. */
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vq = vring_new_virtqueue(lvq->config.num, vdev, lvq->pages,
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lg_notify, callback);
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if (!vq) {
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err = -ENOMEM;
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goto unmap;
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}
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/* Tell the interrupt for this virtqueue to go to the virtio_ring
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* interrupt handler. */
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/* FIXME: We used to have a flag for the Host to tell us we could use
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* the interrupt as a source of randomness: it'd be nice to have that
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* back.. */
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err = request_irq(lvq->config.irq, vring_interrupt, IRQF_SHARED,
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vdev->dev.bus_id, vq);
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if (err)
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goto destroy_vring;
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/* Last of all we hook up our 'struct lguest_vq_info" to the
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* virtqueue's priv pointer. */
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vq->priv = lvq;
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return vq;
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destroy_vring:
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vring_del_virtqueue(vq);
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unmap:
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lguest_unmap(lvq->pages);
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free_lvq:
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kfree(lvq);
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return ERR_PTR(err);
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}
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/*:*/
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/* Cleaning up a virtqueue is easy */
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static void lg_del_vq(struct virtqueue *vq)
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{
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struct lguest_vq_info *lvq = vq->priv;
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/* Release the interrupt */
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free_irq(lvq->config.irq, vq);
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/* Tell virtio_ring.c to free the virtqueue. */
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vring_del_virtqueue(vq);
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/* Unmap the pages containing the ring. */
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lguest_unmap(lvq->pages);
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/* Free our own queue information. */
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kfree(lvq);
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}
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/* The ops structure which hooks everything together. */
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static struct virtio_config_ops lguest_config_ops = {
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.get_features = lg_get_features,
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.set_features = lg_set_features,
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.get = lg_get,
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.set = lg_set,
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.get_status = lg_get_status,
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.set_status = lg_set_status,
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.reset = lg_reset,
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.find_vq = lg_find_vq,
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.del_vq = lg_del_vq,
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};
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/* The root device for the lguest virtio devices. This makes them appear as
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* /sys/devices/lguest/0,1,2 not /sys/devices/0,1,2. */
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static struct device lguest_root = {
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.parent = NULL,
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.bus_id = "lguest",
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};
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/*D:120 This is the core of the lguest bus: actually adding a new device.
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* It's a separate function because it's neater that way, and because an
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* earlier version of the code supported hotplug and unplug. They were removed
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* early on because they were never used.
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*
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* As Andrew Tridgell says, "Untested code is buggy code".
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*
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* It's worth reading this carefully: we start with a pointer to the new device
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* descriptor in the "lguest_devices" page, and the offset into the device
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* descriptor page so we can uniquely identify it if things go badly wrong. */
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static void add_lguest_device(struct lguest_device_desc *d,
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unsigned int offset)
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{
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struct lguest_device *ldev;
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/* Start with zeroed memory; Linux's device layer seems to count on
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* it. */
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ldev = kzalloc(sizeof(*ldev), GFP_KERNEL);
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if (!ldev) {
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printk(KERN_EMERG "Cannot allocate lguest dev %u type %u\n",
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offset, d->type);
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return;
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}
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/* This devices' parent is the lguest/ dir. */
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ldev->vdev.dev.parent = &lguest_root;
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/* We have a unique device index thanks to the dev_index counter. */
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ldev->vdev.id.device = d->type;
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/* We have a simple set of routines for querying the device's
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* configuration information and setting its status. */
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ldev->vdev.config = &lguest_config_ops;
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/* And we remember the device's descriptor for lguest_config_ops. */
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ldev->desc = d;
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/* register_virtio_device() sets up the generic fields for the struct
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* virtio_device and calls device_register(). This makes the bus
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* infrastructure look for a matching driver. */
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if (register_virtio_device(&ldev->vdev) != 0) {
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printk(KERN_ERR "Failed to register lguest dev %u type %u\n",
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offset, d->type);
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kfree(ldev);
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}
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}
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/*D:110 scan_devices() simply iterates through the device page. The type 0 is
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* reserved to mean "end of devices". */
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static void scan_devices(void)
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{
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unsigned int i;
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struct lguest_device_desc *d;
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/* We start at the page beginning, and skip over each entry. */
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for (i = 0; i < PAGE_SIZE; i += desc_size(d)) {
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d = lguest_devices + i;
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/* Once we hit a zero, stop. */
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if (d->type == 0)
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break;
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printk("Device at %i has size %u\n", i, desc_size(d));
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add_lguest_device(d, i);
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}
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}
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/*D:105 Fairly early in boot, lguest_devices_init() is called to set up the
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* lguest device infrastructure. We check that we are a Guest by checking
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* pv_info.name: there are other ways of checking, but this seems most
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* obvious to me.
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*
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* So we can access the "struct lguest_device_desc"s easily, we map that memory
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* and store the pointer in the global "lguest_devices". Then we register a
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* root device from which all our devices will hang (this seems to be the
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* correct sysfs incantation).
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*
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* Finally we call scan_devices() which adds all the devices found in the
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* lguest_devices page. */
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static int __init lguest_devices_init(void)
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{
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if (strcmp(pv_info.name, "lguest") != 0)
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return 0;
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if (device_register(&lguest_root) != 0)
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panic("Could not register lguest root");
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/* Devices are in a single page above top of "normal" mem */
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lguest_devices = lguest_map(max_pfn<<PAGE_SHIFT, 1);
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scan_devices();
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return 0;
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}
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/* We do this after core stuff, but before the drivers. */
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postcore_initcall(lguest_devices_init);
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/*D:150 At this point in the journey we used to now wade through the lguest
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* devices themselves: net, block and console. Since they're all now virtio
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* devices rather than lguest-specific, I've decided to ignore them. Mostly,
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* they're kind of boring. But this does mean you'll never experience the
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* thrill of reading the forbidden love scene buried deep in the block driver.
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*
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* "make Launcher" beckons, where we answer questions like "Where do Guests
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* come from?", and "What do you do when someone asks for optimization?". */
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