Driver for inter-VM shared memory device that now supports interrupts between two guests. The driver defines a counting semaphore and wait_event queue for different synchronization needs of users. Initializing the semaphore count, sending interrupts and waiting are implemented via ioctl calls.
The synchronization mechanisms are simple and rely on existing kernel primitives, but I think they're flexible for synchronization between guests. I'm contemplating more complicated designs that would use the shared memory to store synchronization variables, but thought I would get this initial patch out to get some feedback.
Cheers,
Cam
---
drivers/char/Kconfig | 8 +
drivers/char/Makefile | 2 +
drivers/char/kvm_ivshmem.c | 430 ++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 440 insertions(+), 0 deletions(-)
create mode 100644 drivers/char/kvm_ivshmem.c
diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
index 735bbe2..afa7cb8 100644
--- a/drivers/char/Kconfig
+++ b/drivers/char/Kconfig
@@ -1099,6 +1099,14 @@ config DEVPORT
depends on ISA || PCI
default y
+config KVM_IVSHMEM
+ tristate "Inter-VM Shared Memory Device"
+ depends on PCI
+ default m
+ help
+ This device maps a region of shared memory between the host OS and any
+ number of virtual machines.
+
source "drivers/s390/char/Kconfig"
endmenu
diff --git a/drivers/char/Makefile b/drivers/char/Makefile
index 9caf5b5..021f06b 100644
--- a/drivers/char/Makefile
+++ b/drivers/char/Makefile
@@ -111,6 +111,8 @@ obj-$(CONFIG_PS3_FLASH) += ps3flash.o
obj-$(CONFIG_JS_RTC) += js-rtc.o
js-rtc-y = rtc.o
+obj-$(CONFIG_KVM_IVSHMEM) += kvm_ivshmem.o
+
# Files generated that shall be removed upon make clean
clean-files := consolemap_deftbl.c defkeymap.c
diff --git a/drivers/char/kvm_ivshmem.c b/drivers/char/kvm_ivshmem.c
new file mode 100644
index 0000000..a20a224
--- /dev/null
+++ b/drivers/char/kvm_ivshmem.c
@@ -0,0 +1,430 @@
+/*
+ * drivers/char/kvm_ivshmem.c - driver for KVM Inter-VM shared memory PCI device
+ *
+ * Copyright 2009 Cam Macdonell <cam@xxxxxxxxxxxxxx>
+ *
+ * Based on cirrusfb.c and 8139cp.c:
+ * Copyright 1999-2001 Jeff Garzik
+ * Copyright 2001-2004 Jeff Garzik
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/proc_fs.h>
+#include <linux/smp_lock.h>
+#include <asm/uaccess.h>
+#include <linux/interrupt.h>
+#include <linux/mutex.h>
+
+#define TRUE 1
+#define FALSE 0
+#define KVM_IVSHMEM_DEVICE_MINOR_NUM 0
+
+enum {
+ /* KVM Inter-VM shared memory device register offsets */
+ IntrMask = 0x00, /* Interrupt Mask */
+ IntrStatus = 0x10, /* Interrupt Status */
+ Doorbell = 0x20, /* Doorbell */
+ ShmOK = 1 /* Everything is OK */
+};
+
+typedef struct kvm_ivshmem_device {
+ void __iomem * regs;
+
+ void * base_addr;
+
+ unsigned int regaddr;
+ unsigned int reg_size;
+
+ unsigned int ioaddr;
+ unsigned int ioaddr_size;
+ unsigned int irq;
+
+ bool enabled;
+
+} kvm_ivshmem_device;
+
+static int event_num;
+static struct semaphore sema;
+static wait_queue_head_t wait_queue;
+
+static kvm_ivshmem_device kvm_ivshmem_dev;
+
+static int device_major_nr;
+
+static int kvm_ivshmem_ioctl(struct inode *, struct file *, unsigned int, unsigned long);
+static int kvm_ivshmem_mmap(struct file *, struct vm_area_struct *);
+static int kvm_ivshmem_open(struct inode *, struct file *);
+static int kvm_ivshmem_release(struct inode *, struct file *);
+static ssize_t kvm_ivshmem_read(struct file *, char *, size_t, loff_t *);
+static ssize_t kvm_ivshmem_write(struct file *, const char *, size_t, loff_t *);
+static loff_t kvm_ivshmem_lseek(struct file * filp, loff_t offset, int origin);
+
+enum ivshmem_ioctl { set_sema, down_sema, sema_irq, wait_event, wait_event_irq };
+
+static const struct file_operations kvm_ivshmem_ops = {
+ .owner = THIS_MODULE,
+ .open = kvm_ivshmem_open,
+ .mmap = kvm_ivshmem_mmap,
+ .read = kvm_ivshmem_read,
+ .ioctl = kvm_ivshmem_ioctl,
+ .write = kvm_ivshmem_write,
+ .llseek = kvm_ivshmem_lseek,
+ .release = kvm_ivshmem_release,
+};
+
+static struct pci_device_id kvm_ivshmem_id_table[] = {
+ { 0x1af4, 0x1110, PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0 },
+ { 0 },
+};
+MODULE_DEVICE_TABLE (pci, kvm_ivshmem_id_table);
+
+static void kvm_ivshmem_remove_device(struct pci_dev* pdev);
+static int kvm_ivshmem_probe_device (struct pci_dev *pdev,
+ const struct pci_device_id * ent);
+
+static struct pci_driver kvm_ivshmem_pci_driver = {
+ .name = "kvm-shmem",
+ .id_table = kvm_ivshmem_id_table,
+ .probe = kvm_ivshmem_probe_device,
+ .remove = kvm_ivshmem_remove_device,
+};
+
+static int kvm_ivshmem_ioctl(struct inode * ino, struct file * filp,
+ unsigned int cmd, unsigned long arg)
+{
+
+ int rv;
+
+ switch (cmd) {
+ case set_sema:
+ printk("KVM_IVSHMEM: initialize semaphore\n");
+ printk("KVM_IVSHMEM: args is %ld\n", arg);
+ sema_init(&sema, arg);
+ break;
+ case down_sema:
+ printk("KVM_IVSHMEM: sleeping on semaphore (cmd = %d)\n", cmd);
+ rv = down_interruptible(&sema);
+ printk("KVM_IVSHMEM: waking\n");
+ break;
+ case sema_irq:
+ printk("KVM_IVSHMEM: ringing sema doorbell\n");
+ writeb(cmd, kvm_ivshmem_dev.regs + Doorbell);
+ break;
+ case wait_event:
+ printk("KVM_IVSHMEM: sleeping on event (cmd = %d)\n", cmd);
+ wait_event_interruptible(wait_queue, (event_num == 1));
+ printk("KVM_IVSHMEM: waking\n");
+ event_num = 0;
+ break;
+ case wait_event_irq:
+ printk("KVM_IVSHMEM: ringing wait_event doorbell\n");
+ writeb(cmd, kvm_ivshmem_dev.regs + Doorbell);
+ break;
+ default:
+ printk("KVM_IVSHMEM: bad ioctl\n");
+ }
+
+ return 0;
+}
+
+static ssize_t kvm_ivshmem_read(struct file * filp, char * buffer, size_t len,
+ loff_t * poffset)
+{
+
+ int bytes_read = 0;
+ unsigned long offset;
+
+ offset = *poffset;
+
+ if (!kvm_ivshmem_dev.base_addr) {
+ printk(KERN_ERR "KVM_IVSHMEM: cannot read from ioaddr (NULL)\n");
+ return 0;
+ }
+
+ if (len > kvm_ivshmem_dev.ioaddr_size - offset) {
+ len = kvm_ivshmem_dev.ioaddr_size - offset;
+ }
+
+ if (len == 0) return 0;
+
+ bytes_read = copy_to_user(buffer, kvm_ivshmem_dev.base_addr+offset, len);
+ if (bytes_read > 0) {
+ return -EFAULT;
+ }
+
+ *poffset += len;
+ return len;
+}
+
+static loff_t kvm_ivshmem_lseek(struct file * filp, loff_t offset, int origin)
+{
+
+ loff_t retval = -1;
+
+ switch (origin) {
+ case 1:
+ offset += filp->f_pos;
+ case 0:
+ retval = offset;
+ if (offset > kvm_ivshmem_dev.ioaddr_size) {
+ offset = kvm_ivshmem_dev.ioaddr_size;
+ }
+ filp->f_pos = offset;
+ }
+
+ return retval;
+}
+
+static ssize_t kvm_ivshmem_write(struct file * filp, const char * buffer,
+ size_t len, loff_t * poffset)
+{
+
+ int bytes_written = 0;
+ unsigned long offset;
+
+ offset = *poffset;
+
+ printk(KERN_INFO "KVM_IVSHMEM: trying to write\n");
+ if (!kvm_ivshmem_dev.base_addr) {
+ printk(KERN_ERR "KVM_IVSHMEM: cannot write to ioaddr (NULL)\n");
+ return 0;
+ }
+
+ if (len > kvm_ivshmem_dev.ioaddr_size - offset) {
+ len = kvm_ivshmem_dev.ioaddr_size - offset;
+ }
+
+ printk(KERN_INFO "KVM_IVSHMEM: len is %u\n", (unsigned) len);
+ if (len == 0) return 0;
+
+ bytes_written = copy_from_user(kvm_ivshmem_dev.base_addr+offset,
+ buffer, len);
+ if (bytes_written > 0) {
+ return -EFAULT;
+ }
+
+ printk(KERN_INFO "KVM_IVSHMEM: wrote %u bytes at offset %lu\n",
+ (unsigned) len, offset);
+ *poffset += len;
+ return len;
+}
+
+static irqreturn_t kvm_ivshmem_interrupt (int irq, void *dev_instance)
+{
+ struct kvm_ivshmem_device * dev = dev_instance;
+ u16 status;
+
+ if (unlikely(dev == NULL))
+ return IRQ_NONE;
+
+ status = readw(dev->regs + IntrStatus);
+ if (!status || (status == 0xFFFF))
+ return IRQ_NONE;
+
+ /* depending on the message we wake different structures */
+ if (status == sema_irq) {
+ up(&sema);
+ } else if (status == wait_event_irq) {
+ event_num = 1;
+ wake_up_interruptible(&wait_queue);
+ }
+
+ printk(KERN_INFO "KVM_IVSHMEM: interrupt (status = 0x%04x)\n",
+ status);
+
+ return IRQ_HANDLED;
+}
+
+static int kvm_ivshmem_probe_device (struct pci_dev *pdev,
+ const struct pci_device_id * ent) {
+
+ int result;
+
+ printk("KVM_IVSHMEM: Probing for KVM_IVSHMEM Device\n");
+
+ result = pci_enable_device(pdev);
+ if (result) {
+ printk(KERN_ERR "Cannot probe KVM_IVSHMEM device %s: error %d\n",
+ pci_name(pdev), result);
+ return result;
+ }
+
+ result = pci_request_regions(pdev, "kvm_ivshmem");
+ if (result < 0) {
+ printk(KERN_ERR "KVM_IVSHMEM: cannot request regions\n");
+ goto pci_disable;
+ } else printk(KERN_ERR "KVM_IVSHMEM: result is %d\n", result);
+
+ kvm_ivshmem_dev.ioaddr = pci_resource_start(pdev, 1);
+ kvm_ivshmem_dev.ioaddr_size = pci_resource_len(pdev, 1);
+
+ kvm_ivshmem_dev.base_addr = pci_iomap(pdev, 1, 0);
+ printk(KERN_INFO "KVM_IVSHMEM: iomap base = 0x%lu \n",
+ (unsigned long) kvm_ivshmem_dev.base_addr);
+
+ if (!kvm_ivshmem_dev.base_addr) {
+ printk(KERN_ERR "KVM_IVSHMEM: cannot iomap region of size %d\n",
+ kvm_ivshmem_dev.ioaddr_size);
+ goto pci_release;
+ }
+
+ printk(KERN_INFO "KVM_IVSHMEM: ioaddr = %x ioaddr_size = %d\n",
+ kvm_ivshmem_dev.ioaddr, kvm_ivshmem_dev.ioaddr_size);
+
+ kvm_ivshmem_dev.regaddr = pci_resource_start(pdev, 0);
+ kvm_ivshmem_dev.reg_size = pci_resource_len(pdev, 0);
+ kvm_ivshmem_dev.regs = pci_iomap(pdev, 0, 0x100);
+
+ if (!kvm_ivshmem_dev.regs) {
+ printk(KERN_ERR "KVM_IVSHMEM: cannot ioremap registers of size %d\n",
+ kvm_ivshmem_dev.reg_size);
+ goto reg_release;
+ }
+
+ /* set all masks to on */
+ writew(0xffff, kvm_ivshmem_dev.regs + IntrMask);
+
+ /* by default initialize semaphore to 0 */
+ sema_init(&sema, 0);
+
+ init_waitqueue_head(&wait_queue);
+ event_num = 0;
+
+ printk(KERN_INFO "KVM_IVSHMEM: irq = %u regaddr = %x reg_size = %d\n",
+ pdev->irq, kvm_ivshmem_dev.regaddr, kvm_ivshmem_dev.reg_size);
+
+ if (request_irq(pdev->irq, kvm_ivshmem_interrupt, IRQF_SHARED,
+ "kvm_ivshmem", &kvm_ivshmem_dev)) {
+ printk(KERN_ERR "KVM_IVSHMEM: cannot get interrupt %d\n", pdev->irq);
+ }
+
+ return 0;
+
+
+reg_release:
+ pci_iounmap(pdev, kvm_ivshmem_dev.base_addr);
+pci_release:
+ pci_release_regions(pdev);
+pci_disable:
+ pci_disable_device(pdev);
+ return -EBUSY;
+
+}
+
+static void kvm_ivshmem_remove_device(struct pci_dev* pdev)
+{
+
+ printk(KERN_INFO "Unregister kvm_ivshmem device.\n");
+ free_irq(pdev->irq,&kvm_ivshmem_dev);
+ pci_iounmap(pdev, kvm_ivshmem_dev.regs);
+ pci_iounmap(pdev, kvm_ivshmem_dev.base_addr);
+ pci_release_regions(pdev);
+ pci_disable_device(pdev);
+
+}
+
+static void __exit kvm_ivshmem_cleanup_module (void)
+{
+ pci_unregister_driver (&kvm_ivshmem_pci_driver);
+ unregister_chrdev(device_major_nr, "kvm_ivshmem");
+}
+
+static int __init kvm_ivshmem_init_module (void)
+{
+
+ int err = -ENOMEM;
+
+ /* Register device node ops. */
+ err = register_chrdev(0, "kvm_ivshmem", &kvm_ivshmem_ops);
+ if (err < 0) {
+ printk(KERN_ERR "Unable to register kvm_ivshmem device\n");
+ return err;
+ }
+ device_major_nr = err;
+ printk("KVM_IVSHMEM: Major device number is: %d\n", device_major_nr);
+ kvm_ivshmem_dev.enabled=FALSE;
+
+ err = pci_register_driver(&kvm_ivshmem_pci_driver);
+ if (err < 0) {
+ goto error;
+ }
+
+ return 0;
+
+error:
+ unregister_chrdev(device_major_nr, "kvm_ivshmem");
+ return err;
+}
+
+
+static int kvm_ivshmem_open(struct inode * inode, struct file * filp)
+{
+
+ printk(KERN_INFO "Opening kvm_ivshmem device\n");
+
+ if (MINOR(inode->i_rdev) != KVM_IVSHMEM_DEVICE_MINOR_NUM) {
+ printk(KERN_INFO "minor number is %d\n", KVM_IVSHMEM_DEVICE_MINOR_NUM);
+ return -ENODEV;
+ }
+
+ return 0;
+}
+
+static int kvm_ivshmem_release(struct inode * inode, struct file * filp)
+{
+
+ return 0;
+}
+
+static int kvm_ivshmem_mmap(struct file *filp, struct vm_area_struct * vma)
+{
+
+ unsigned long len;
+ unsigned long off;
+ unsigned long start;
+
+ lock_kernel();
+
+ off = vma->vm_pgoff << PAGE_SHIFT;
+ start = kvm_ivshmem_dev.ioaddr;
+
+ len=PAGE_ALIGN((start & ~PAGE_MASK) + kvm_ivshmem_dev.ioaddr_size);
+ start &= PAGE_MASK;
+
+ printk(KERN_INFO "%lu - %lu + %lu\n",vma->vm_end ,vma->vm_start, off);
+ printk(KERN_INFO "%lu > %lu\n",(vma->vm_end - vma->vm_start + off), len);
+
+ if ((vma->vm_end - vma->vm_start + off) > len) {
+ unlock_kernel();
+ return -EINVAL;
+ }
+
+ off += start;
+ vma->vm_pgoff = off >> PAGE_SHIFT;
+
+ vma->vm_flags |= VM_SHARED|VM_RESERVED;
+
+ if(io_remap_pfn_range(vma, vma->vm_start,
+ off >> PAGE_SHIFT, vma->vm_end - vma->vm_start,
+ vma->vm_page_prot))
+ {
+ printk("mmap failed\n");
+ unlock_kernel();
+ return -ENXIO;
+ }
+ unlock_kernel();
+
+ return 0;
+}
+
+module_init(kvm_ivshmem_init_module);
+module_exit(kvm_ivshmem_cleanup_module);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Cam Macdonell <cam@xxxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("KVM inter-VM shared memory module");
+MODULE_VERSION("1.0");
--
1.6.0.6
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