[Xen-users] IOCTL_PRIVCMD_MMAPBATCH can't mmap more than 160 pages?

[Guanglin Xu <mzguanglin@xxxxxxxxx>]

Hi,

I want to map the whole guest memory by xc_map_foreign_range() in
libxc, but I failed when the mmaping number of pages exceeded 160
pages (640KB).

Can anyone help, 1.figure out the reason; 2.try the same
xc_map_foreign_range() codes if you can use IOCTL_PRIVCMD_MMAPBATCH2
and share you result ? Thank you.

My configurations:
Host: Ubuntu 12.04 64bit
Xen 4.1.2
Linux Kernel: 3.5.0-23, support IOCTL_PRIVCMD_MMAPBATCH only, rather
than IOCTL_PRIVCMD_MMAPBATCH2.
Guest: Windows XP SP2  32bit

Source code:
#define MEM_PAGE_MAX_MAP (40 * XC_PAGE_SIZE)
for (i=0; i < region_num; i++) {

    unsigned long pfn_offset = i * MEM_PAGE_MAX_MAP / XC_PAGE_SIZE;
    int map_size =
(last_region_size==0||i<region_num-1)?MEM_PAGE_MAX_MAP:last_region_size;

    printf("foreign_range "
    "pfn_offset = %ld, map_size = %ld \n"
    , pfn_offset,  map_size);

    void *memory = xc_map_foreign_range(xchandle,  domainid, map_size,
PROT_READ, pfn_offset);
        if (MAP_FAILED == memory || NULL == memory) {
            dbprint("xc_map_foreign_range failed on pfn_offset=%d\n",
pfn_offset);
            return;
        }
}

Output:
foreign_range pfn_offset = 0, map_size = 163840
foreign_range pfn_offset = 40, map_size = 163840
foreign_range pfn_offset = 80, map_size = 163840
foreign_range pfn_offset = 120, map_size = 163840
foreign_range pfn_offset = 160, map_size = 16384
xc_map_foreign_range failed on pfn_offset=160


I have debuged libxc, too. And I find that when I have mmaped 160
pages, subsequent invoking of  ioctl(fd, IOCTL_PRIVCMD_MMAPBATCH,
&ioctlx) will set pfn[n] = 140737344202616, never conform to arr[n]
any more.

libxc code:
xc_linux_osdep.c:277
            memcpy(pfn, arr, num * sizeof(*arr));

            ioctlx.num = num;
            ioctlx.dom = dom;
            ioctlx.addr = (unsigned long)addr;
            ioctlx.arr = pfn;

            rc = ioctl(fd, IOCTL_PRIVCMD_MMAPBATCH, &ioctlx);

            rc = rc < 0 ? -errno : 0;

            for ( i = 0; i < num; ++i )
            {
                switch ( pfn[i] ^ arr[i] )
                {
                case 0:
                    err[i] = rc != -ENOENT ? rc : 0;
                    continue;
                default:
                    err[i] = -EINVAL;
                    continue;
           }

Also, I have tried to look into kernel/drivers/xen/privcmd.c, but the
data flow in the ioctl interface seems complex to me. So I haven't
figured out the reason even nnow.

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