Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 9a2bb7f4 authored by Avi Kivity's avatar Avi Kivity
Browse files

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: default avatarAvi Kivity <avi@qumranet.com>
parent 1ea252af

drivers/kvm/kvm.h

+1 −0
Original line number Diff line number Diff line
@@ -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)

drivers/kvm/kvm_main.c

+40 −14
Original line number Diff line number Diff line
@@ -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;

include/linux/kvm.h

+3 −3
Original line number Diff line number Diff line
@@ -11,7 +11,7 @@ 
#include <asm/types.h>

#include <linux/ioctl.h>



#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)