KVM: Use a shared page for kernel/user communication when runing a vcpu
Instead of passing a 'struct kvm_run' back and forth between the kernel and
userspace, allocate a page and allow the user to mmap() it. This reduces
needless copying and makes the interface expandable by providing lots of
free space.
Signed-off-by: Avi Kivity <avi@qumranet.com>
diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 946ed86..42be8a8 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -355,6 +355,8 @@
kvm_mmu_destroy(vcpu);
vcpu_put(vcpu);
kvm_arch_ops->vcpu_free(vcpu);
+ free_page((unsigned long)vcpu->run);
+ vcpu->run = NULL;
}
static void kvm_free_vcpus(struct kvm *kvm)
@@ -1887,6 +1889,33 @@
return r;
}
+static struct page *kvm_vcpu_nopage(struct vm_area_struct *vma,
+ unsigned long address,
+ int *type)
+{
+ struct kvm_vcpu *vcpu = vma->vm_file->private_data;
+ unsigned long pgoff;
+ struct page *page;
+
+ *type = VM_FAULT_MINOR;
+ pgoff = ((address - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
+ if (pgoff != 0)
+ return NOPAGE_SIGBUS;
+ page = virt_to_page(vcpu->run);
+ get_page(page);
+ return page;
+}
+
+static struct vm_operations_struct kvm_vcpu_vm_ops = {
+ .nopage = kvm_vcpu_nopage,
+};
+
+static int kvm_vcpu_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ vma->vm_ops = &kvm_vcpu_vm_ops;
+ return 0;
+}
+
static int kvm_vcpu_release(struct inode *inode, struct file *filp)
{
struct kvm_vcpu *vcpu = filp->private_data;
@@ -1899,6 +1928,7 @@
.release = kvm_vcpu_release,
.unlocked_ioctl = kvm_vcpu_ioctl,
.compat_ioctl = kvm_vcpu_ioctl,
+ .mmap = kvm_vcpu_mmap,
};
/*
@@ -1947,6 +1977,7 @@
{
int r;
struct kvm_vcpu *vcpu;
+ struct page *page;
r = -EINVAL;
if (!valid_vcpu(n))
@@ -1961,6 +1992,12 @@
return -EEXIST;
}
+ page = alloc_page(GFP_KERNEL | __GFP_ZERO);
+ r = -ENOMEM;
+ if (!page)
+ goto out_unlock;
+ vcpu->run = page_address(page);
+
vcpu->host_fx_image = (char*)ALIGN((hva_t)vcpu->fx_buf,
FX_IMAGE_ALIGN);
vcpu->guest_fx_image = vcpu->host_fx_image + FX_IMAGE_SIZE;
@@ -1990,6 +2027,7 @@
out_free_vcpus:
kvm_free_vcpu(vcpu);
+out_unlock:
mutex_unlock(&vcpu->mutex);
out:
return r;
@@ -2003,21 +2041,9 @@
int r = -EINVAL;
switch (ioctl) {
- case KVM_RUN: {
- struct kvm_run kvm_run;
-
- r = -EFAULT;
- if (copy_from_user(&kvm_run, argp, sizeof kvm_run))
- goto out;
- r = kvm_vcpu_ioctl_run(vcpu, &kvm_run);
- if (r < 0 && r != -EINTR)
- goto out;
- if (copy_to_user(argp, &kvm_run, sizeof kvm_run)) {
- r = -EFAULT;
- goto out;
- }
+ case KVM_RUN:
+ r = kvm_vcpu_ioctl_run(vcpu, vcpu->run);
break;
- }
case KVM_GET_REGS: {
struct kvm_regs kvm_regs;