From 9a2bb7f486dc639a1cf2ad803bf2227f0dc0809d Mon Sep 17 00:00:00 2001 From: Avi Kivity Date: Thu, 22 Feb 2007 12:58:31 +0200 Subject: [PATCH] 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 --- drivers/kvm/kvm.h | 1 + drivers/kvm/kvm_main.c | 54 +++++++++++++++++++++++++++++++----------- include/linux/kvm.h | 6 ++--- 3 files changed, 44 insertions(+), 17 deletions(-) diff --git a/drivers/kvm/kvm.h b/drivers/kvm/kvm.h index 0d122bf889db..901b8d917b55 100644 --- a/drivers/kvm/kvm.h +++ b/drivers/kvm/kvm.h @@ -228,6 +228,7 @@ struct kvm_vcpu { struct mutex mutex; int cpu; int launched; + struct kvm_run *run; int interrupt_window_open; unsigned long irq_summary; /* bit vector: 1 per word in irq_pending */ #define NR_IRQ_WORDS KVM_IRQ_BITMAP_SIZE(unsigned long) diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c index 946ed86a0595..42be8a8f299d 100644 --- a/drivers/kvm/kvm_main.c +++ b/drivers/kvm/kvm_main.c @@ -355,6 +355,8 @@ static void kvm_free_vcpu(struct kvm_vcpu *vcpu) 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 @@ static int kvm_vcpu_ioctl_debug_guest(struct kvm_vcpu *vcpu, 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 @@ static struct file_operations kvm_vcpu_fops = { .release = kvm_vcpu_release, .unlocked_ioctl = kvm_vcpu_ioctl, .compat_ioctl = kvm_vcpu_ioctl, + .mmap = kvm_vcpu_mmap, }; /* @@ -1947,6 +1977,7 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, int n) { int r; struct kvm_vcpu *vcpu; + struct page *page; r = -EINVAL; if (!valid_vcpu(n)) @@ -1961,6 +1992,12 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, int n) 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 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, int n) out_free_vcpus: kvm_free_vcpu(vcpu); +out_unlock: mutex_unlock(&vcpu->mutex); out: return r; @@ -2003,21 +2041,9 @@ static long kvm_vcpu_ioctl(struct file *filp, 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; diff --git a/include/linux/kvm.h b/include/linux/kvm.h index 275354ffa1cb..d88e7508ee0a 100644 --- a/include/linux/kvm.h +++ b/include/linux/kvm.h @@ -11,7 +11,7 @@ #include #include -#define KVM_API_VERSION 4 +#define KVM_API_VERSION 5 /* * Architectural interrupt line count, and the size of the bitmap needed @@ -49,7 +49,7 @@ enum kvm_exit_reason { KVM_EXIT_SHUTDOWN = 8, }; -/* for KVM_RUN */ +/* for KVM_RUN, returned by mmap(vcpu_fd, offset=0) */ struct kvm_run { /* in */ __u32 emulated; /* skip current instruction */ @@ -233,7 +233,7 @@ struct kvm_dirty_log { /* * ioctls for vcpu fds */ -#define KVM_RUN _IOWR(KVMIO, 2, struct kvm_run) +#define KVM_RUN _IO(KVMIO, 16) #define KVM_GET_REGS _IOR(KVMIO, 3, struct kvm_regs) #define KVM_SET_REGS _IOW(KVMIO, 4, struct kvm_regs) #define KVM_GET_SREGS _IOR(KVMIO, 5, struct kvm_sregs) -- 2.34.1