search for: num_descs

Hello Rusty, while playing with your virtio descriptor code, I realized that the desc_pages data structure is not 64 bit safe. struct lguest_desc desc[NUM_DESCS] can be smaller than a page, as struct lguest_desc is 24 bytes on 64bit systems. Lets add a char padding to make the next page really page aligned. Btw. the new_io_desc.patch does not apply on current git. What base should I use? --- lguest_virtio.c.old 2007-08-17 10:15:05.000000000 +0200 ++...

Hello Rusty, while playing with your virtio descriptor code, I realized that the desc_pages data structure is not 64 bit safe. struct lguest_desc desc[NUM_DESCS] can be smaller than a page, as struct lguest_desc is 24 bytes on 64bit systems. Lets add a char padding to make the next page really page aligned. Btw. the new_io_desc.patch does not apply on current git. What base should I use? --- lguest_virtio.c.old 2007-08-17 10:15:05.000000000 +0200 ++...

...gesize()) +#define PAGE_ALIGN(addr) (((addr) + PAGE_SIZE - 1) & ~(PAGE_SIZE - 1)) + #include "linux/lguest_launcher.h" #include "linux/virtio_config.h" #include "linux/virtio_net.h" @@ -1036,7 +1041,7 @@ static void add_virtqueue(struct device *dev, unsigned int num_descs, void *p; /* First we need some pages for this virtqueue. */ - pages = (vring_size(num_descs, getpagesize()) + getpagesize() - 1) + pages = (vring_size(num_descs) + getpagesize() - 1) / getpagesize(); p = get_pages(pages); @@ -1046,7 +1051,7 @@ static void add_virtqueue(struct device *...

...gesize()) +#define PAGE_ALIGN(addr) (((addr) + PAGE_SIZE - 1) & ~(PAGE_SIZE - 1)) + #include "linux/lguest_launcher.h" #include "linux/virtio_config.h" #include "linux/virtio_net.h" @@ -1036,7 +1041,7 @@ static void add_virtqueue(struct device *dev, unsigned int num_descs, void *p; /* First we need some pages for this virtqueue. */ - pages = (vring_size(num_descs, getpagesize()) + getpagesize() - 1) + pages = (vring_size(num_descs) + getpagesize() - 1) / getpagesize(); p = get_pages(pages); @@ -1046,7 +1051,7 @@ static void add_virtqueue(struct device *...

...d) { + kunmap(vr->used_page); + put_page(vr->used_page); + } + + kfree(vr); + return 0; +} + +static const struct file_operations vring_fops = { + .release = vring_release, + .write = vring_write, + .poll = vring_poll, +}; + +asmlinkage long sys_vringfd(void __user *addr, + unsigned num_descs, + u16 __user *last_used) +{ + int fd, err; + struct file *filp; + struct vring_info *vr; + + /* Must be a power of two, and representable by u16 */ + if (!num_descs || (num_descs & (num_descs-1)) || num_descs > 65536) { + err = -EINVAL; + goto out; + } + + fd = get_unused_fd(); + if...

...d) { + kunmap(vr->used_page); + put_page(vr->used_page); + } + + kfree(vr); + return 0; +} + +static const struct file_operations vring_fops = { + .release = vring_release, + .write = vring_write, + .poll = vring_poll, +}; + +asmlinkage long sys_vringfd(void __user *addr, + unsigned num_descs, + u16 __user *last_used) +{ + int fd, err; + struct file *filp; + struct vring_info *vr; + + /* Must be a power of two, and representable by u16 */ + if (!num_descs || (num_descs & (num_descs-1)) || num_descs > 65536) { + err = -EINVAL; + goto out; + } + + fd = get_unused_fd(); + if...

...he descriptor entries and the "pending" ring buffer, and write to the "used" ring buffer. We can use page protection to share these if we arrange things carefully, like so: struct desc_pages { /* Page of descriptors. */ struct lguest_desc desc[NUM_DESCS]; /* Next page: how we tell other side what buffers are available. */ unsigned int avail_idx; unsigned int available[NUM_DESCS]; char pad[PAGE_SIZE - (NUM_DESCS+1) * sizeof(unsigned int)]; /* Third page: how other side tells us what'...

...he descriptor entries and the "pending" ring buffer, and write to the "used" ring buffer. We can use page protection to share these if we arrange things carefully, like so: struct desc_pages { /* Page of descriptors. */ struct lguest_desc desc[NUM_DESCS]; /* Next page: how we tell other side what buffers are available. */ unsigned int avail_idx; unsigned int available[NUM_DESCS]; char pad[PAGE_SIZE - (NUM_DESCS+1) * sizeof(unsigned int)]; /* Third page: how other side tells us what'...

...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 +1166,7 @@ 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 +1183,7 @@ static void add_virt...

...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 +1166,7 @@ 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 +1183,7 @@ static void add_virt...

...dds a virtqueue to a device. We specify how many descriptors - * the virtqueue is to have. */ +/* Each device descriptor is followed by the description of its virtqueues. We + * specify how many descriptors the virtqueue is to have. */ static void add_virtqueue(struct device *dev, unsigned int num_descs, void (*handle_output)(int fd, struct virtqueue *me)) { @@ -1053,9 +1043,15 @@ static void add_virtqueue(struct device *dev, unsigned int num_descs, /* Initialize the vring. */ vring_init(&vq->vring, num_descs, p, getpagesize()); - /* Add the configuration inf...

...dds a virtqueue to a device. We specify how many descriptors - * the virtqueue is to have. */ +/* Each device descriptor is followed by the description of its virtqueues. We + * specify how many descriptors the virtqueue is to have. */ static void add_virtqueue(struct device *dev, unsigned int num_descs, void (*handle_output)(int fd, struct virtqueue *me)) { @@ -1053,9 +1043,15 @@ static void add_virtqueue(struct device *dev, unsigned int num_descs, /* Initialize the vring. */ vring_init(&vq->vring, num_descs, p, getpagesize()); - /* Add the configuration inf...

virtio allows drivers to suppress callbacks (ie. interrupts) for efficiency (no locking, it's just an optimization). There's a similar mechanism for the host to suppress notifications coming from the guest: in that case, we ignore the suppression if the ring is completely full. It turns out that life is simpler if the host similarly ignores callback suppression when the ring is

virtio allows drivers to suppress callbacks (ie. interrupts) for efficiency (no locking, it's just an optimization). There's a similar mechanism for the host to suppress notifications coming from the guest: in that case, we ignore the suppression if the ring is completely full. It turns out that life is simpler if the host similarly ignores callback suppression when the ring is

Hi all, These are the patches I'm planning to submit for 2.6.24. Comments gratefully accepted. Along with the usual cleanups and improvements are Jes' de-i386-ification patches, and a new "virtio" mechanism designed to be shared with KVM (and hopefully other hypervisors). Cheers, Rusty. Documentation/lguest/Makefile | 30 Documentation/lguest/lguest.c

Hi all, These are the patches I'm planning to submit for 2.6.24. Comments gratefully accepted. Along with the usual cleanups and improvements are Jes' de-i386-ification patches, and a new "virtio" mechanism designed to be shared with KVM (and hopefully other hypervisors). Cheers, Rusty. Documentation/lguest/Makefile | 30 Documentation/lguest/lguest.c