Re: [Qemu-devel] DAX can not work on virtual nvdimm device

[Xiao Guangrong <guangrong.xiao@linux.intel.com>]

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On 08/31/2016 01:09 AM, Dan Williams wrote:

>
> Can you post your exact reproduction steps?  This test is not failing for me.
>

Sure.

1. make the guest kernel based on your tree, the top commit is
    10d7902fa0e82b (dax: unmap/truncate on device shutdown) and
    the config file can be found in this thread.

2. add guest kernel command line: memmap=6G!10G

3: start the guest:
    x86_64-softmmu/qemu-system-x86_64 -machine pc,nvdimm --enable-kvm \
    -smp 16 -m 32G,maxmem=100G,slots=100 /other/VMs/centos6.img -monitor stdio

4: in guest:
    mkfs.ext4 /dev/pmem0
    mount -o dax /dev/pmem0  /mnt/pmem/
    echo > /mnt/pmem/xxx
    ./mmap /mnt/pmem/xxx
    ./read /mnt/pmem/xxx

   The source code of mmap and read has been attached in this mail.

   Hopefully, you can detect the error triggered by read test.

Thanks!

[-- Attachment #2: read.c --]
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#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>

int main(int argc, char *argv[])
{
	char *filename;

	if (argc < 2) {
		printf("arg: filename.\n");
		return -1;
	}

	filename = argv[1];
	printf("test on %s.\n", filename);

	int fd = open(filename, O_RDWR);

	if (fd < 0) {
		perror("open");
		return -1;
	}

	int count = 0;

	while (1) {
		ssize_t ret;
		char buf;

		ret = read(fd, &buf, sizeof(buf));
		if (ret < 0) {
			perror("READ");
			return -1;
		}

		if (ret == 0)
			break;
		if (ret != sizeof(buf)) {
			printf("Count %x Ret %lx sizeof(buf) %lx.\n",
				count, ret, sizeof(buf));
			return -1;
		}

		count++;
		printf("%c", buf);
	}

	printf("\n Good Read.\n");
	return 0;
}

[-- Attachment #3: mmap.c --]
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#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <unistd.h>

static void write_test(char *buf, int size)
{
	int i;

	printf("Try to write %p for %x size.\n", buf, size);
	for (i = 0; i < size; i++)
		buf[i] = (char)(i & 0xFF);
	printf("Write Done.\n");
}

static void read_test(char *buf, int size)
{
	int i;

	printf("Try to read %p for %x size.\n", buf, size);
	for (i = 0; i < size; i++)
		if (buf[i] != (char)(i & 0xFF)) {
			printf("Read Check failed.\n");
			printf("Index %x, %c expect %x.\n", i, buf[i], i & 0xFF);
			exit(-1);
		}
	printf("Read Done.\n");
}

static void fread_test(int fd, int size)
{
	char buf;
	int i;

	i = lseek(fd, 0, SEEK_END);
	printf("End: %x.\n", i);

	i = lseek(fd, 0, SEEK_SET);
	if (i != 0) {
		perror("seek");
		exit(-1);
	}

	printf("Try to fread fd=%d size %x sizeof(buf) %ld.\n", fd, size,
		sizeof(buf));

	for (i = 0; i < size; i++) {
		int ret;

		ret = read(fd, &buf, sizeof(buf));
		if (ret != sizeof(buf)) {
			printf("Read failed, offset %x, ret %d ftell %ld.\n",
				i, ret, lseek(fd, 0, SEEK_CUR));
			perror("read");
			exit(-1);
		}
		if (buf != (char)(i & 0xFF)) {
			printf("Read Check failed.\n");
			printf("Index %x, %c expect %x.\n", i, buf, i & 0xFF);
			exit (-1);
		}
	}

	printf("Fread Done.\n");
}

int main(int argc, char *argv[])
{
	char *filename;
	char *buf;
	int fd;

	if (argc < 2) {
		printf("arg: filename.\n");
		return -1;
	}

	filename = argv[1];
	printf("mmap test on %s.\n", filename);

	fd = open(filename, O_RDWR);
	if (fd < 0) {
		perror("open");
		return -1;
	}

	if (lseek(fd, 0x1000, SEEK_SET) != 0x1000) {
		perror("seek");
		return -1;
	}

	if (ftruncate(fd, 0x1000) != 0) {
		perror("ftruncate");
		return -1;
	}

//	return 0;

	buf = mmap(NULL, 0x1000, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
	if (buf == MAP_FAILED) {
		perror("mmap");
		return -1;
	}

	write_test(buf, 0x1000);
	read_test(buf, 0x1000);
	msync(buf, 0x1000, MS_SYNC);
	fread_test(fd, 0x1000);

	close(fd);

	return 0;
}