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

[Guanglin Xu <mzguanglin@xxxxxxxxx>]

I've tried IOCTL_PRIVCMD_MMAPBATCH_V2 by installing kernel 3.8, but
failed again.

rc = ioctl(fd, IOCTL_PRIVCMD_MMAPBATCH_V2, &ioctlx);

While the ioctl() always returns 0 whatever number of pages have been
mmaped, the ioctlx.err[] array items would be assigned EINVAL if more
than 160 pages have been mmaped.

Can any one help?

2013/7/27 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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