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Commit 28fd6d7f authored by Rusty Russell's avatar Rusty Russell
Browse files

lguest: virtio-rng support 



This is a simple patch to add support for the virtio "hardware random
generator" to lguest.  It gets about 1.2 MB/sec reading from /dev/hwrng
in the guest.

Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent dec6a2be

Documentation/lguest/lguest.c

+90 −0
Original line number Original line Diff line number Diff line
@@ -41,6 +41,7 @@ 
#include "linux/virtio_net.h"

#include "linux/virtio_net.h"

#include "linux/virtio_blk.h"

#include "linux/virtio_blk.h"

#include "linux/virtio_console.h"

#include "linux/virtio_console.h"

#include "linux/virtio_rng.h"

#include "linux/virtio_ring.h"

#include "linux/virtio_ring.h"

#include "asm-x86/bootparam.h"

#include "asm-x86/bootparam.h"

/*L:110 We can ignore the 39 include files we need for this program, but I do

/*L:110 We can ignore the 39 include files we need for this program, but I do
@@ -199,6 +200,33 @@ static void *_convert(struct iovec *iov, size_t size, size_t align, 
#define le32_to_cpu(v32) (v32)

#define le32_to_cpu(v32) (v32)

#define le64_to_cpu(v64) (v64)

#define le64_to_cpu(v64) (v64)





/* Is this iovec empty? */

static bool iov_empty(const struct iovec iov[], unsigned int num_iov)

{

	unsigned int i;



	for (i = 0; i < num_iov; i++)

		if (iov[i].iov_len)

			return false;

	return true;

}



/* Take len bytes from the front of this iovec. */

static void iov_consume(struct iovec iov[], unsigned num_iov, unsigned len)

{

	unsigned int i;



	for (i = 0; i < num_iov; i++) {

		unsigned int used;



		used = iov[i].iov_len < len ? iov[i].iov_len : len;

		iov[i].iov_base += used;

		iov[i].iov_len -= used;

		len -= used;

	}

	assert(len == 0);

}



/* The device virtqueue descriptors are followed by feature bitmasks. */

/* The device virtqueue descriptors are followed by feature bitmasks. */

static u8 *get_feature_bits(struct device *dev)

static u8 *get_feature_bits(struct device *dev)

{

{
@@ -1678,6 +1706,64 @@ static void setup_block_file(const char *filename) 
	verbose("device %u: virtblock %llu sectors\n",

	verbose("device %u: virtblock %llu sectors\n",

		devices.device_num, le64_to_cpu(conf.capacity));

		devices.device_num, le64_to_cpu(conf.capacity));

}

}



/* Our random number generator device reads from /dev/random into the Guest's

 * input buffers.  The usual case is that the Guest doesn't want random numbers

 * and so has no buffers although /dev/random is still readable, whereas

 * console is the reverse.

 *

 * The same logic applies, however. */

static bool handle_rng_input(int fd, struct device *dev)

{

	int len;

	unsigned int head, in_num, out_num, totlen = 0;

	struct iovec iov[dev->vq->vring.num];



	/* First we need a buffer from the Guests's virtqueue. */

	head = get_vq_desc(dev->vq, iov, &out_num, &in_num);



	/* If they're not ready for input, stop listening to this file

	 * descriptor.  We'll start again once they add an input buffer. */

	if (head == dev->vq->vring.num)

		return false;



	if (out_num)

		errx(1, "Output buffers in rng?");



	/* This is why we convert to iovecs: the readv() call uses them, and so

	 * it reads straight into the Guest's buffer.  We loop to make sure we

	 * fill it. */

	while (!iov_empty(iov, in_num)) {

		len = readv(dev->fd, iov, in_num);

		if (len <= 0)

			err(1, "Read from /dev/random gave %i", len);

		iov_consume(iov, in_num, len);

		totlen += len;

	}



	/* Tell the Guest about the new input. */

	add_used_and_trigger(fd, dev->vq, head, totlen);



	/* Everything went OK! */

	return true;

}



/* And this creates a "hardware" random number device for the Guest. */

static void setup_rng(void)

{

	struct device *dev;

	int fd;



	fd = open_or_die("/dev/random", O_RDONLY);



	/* The device responds to return from I/O thread. */

	dev = new_device("rng", VIRTIO_ID_RNG, fd, handle_rng_input);



	/* The device has one virtqueue, where the Guest places inbufs. */

	add_virtqueue(dev, VIRTQUEUE_NUM, enable_fd);



	verbose("device %u: rng\n", devices.device_num++);

}

/* That's the end of device setup. */

/* That's the end of device setup. */





/*L:230 Reboot is pretty easy: clean up and exec() the Launcher afresh. */

/*L:230 Reboot is pretty easy: clean up and exec() the Launcher afresh. */
@@ -1748,6 +1834,7 @@ static struct option opts[] = { 
	{ "verbose", 0, NULL, 'v' },

	{ "verbose", 0, NULL, 'v' },

	{ "tunnet", 1, NULL, 't' },

	{ "tunnet", 1, NULL, 't' },

	{ "block", 1, NULL, 'b' },

	{ "block", 1, NULL, 'b' },

	{ "rng", 0, NULL, 'r' },

	{ "initrd", 1, NULL, 'i' },

	{ "initrd", 1, NULL, 'i' },

	{ NULL },

	{ NULL },

};

};
@@ -1822,6 +1909,9 @@ int main(int argc, char *argv[]) 
		case 'b':

		case 'b':

			setup_block_file(optarg);

			setup_block_file(optarg);

			break;

			break;

		case 'r':

			setup_rng();

			break;

		case 'i':

		case 'i':

			initrd_name = optarg;

			initrd_name = optarg;

			break;

			break;