Re: [Xen-devel] [PATCH v4] xen/privcmd: add IOCTL_PRIVCMD_MMAP_RESOURCE

[Julien Grall <julien.grall@xxxxxxx>]

Hi,

On 10/04/18 08:58, Paul Durrant wrote:
> +static long privcmd_ioctl_mmap_resource(struct file *file, void __user *udata)
> +{
> +       struct privcmd_data *data = file->private_data;
> +       struct mm_struct *mm = current->mm;
> +       struct vm_area_struct *vma;
> +       struct privcmd_mmap_resource kdata;
> +       xen_pfn_t *pfns = NULL;
> +       struct xen_mem_acquire_resource xdata;
> +       int rc;
> +
> +       if (copy_from_user(&kdata, udata, sizeof(kdata)))
> +               return -EFAULT;
> +
> +       /* If restriction is in place, check the domid matches */
> +       if (data->domid != DOMID_INVALID && data->domid != kdata.dom)
> +               return -EPERM;
> +
> +       down_write(&mm->mmap_sem);
> +
> +       vma = find_vma(mm, kdata.addr);
> +       if (!vma || vma->vm_ops != &privcmd_vm_ops) {
> +               rc = -EINVAL;
> +               goto out;
> +       }
> +
> +       pfns = kcalloc(kdata.num, sizeof(*pfns), GFP_KERNEL);
> +       if (!pfns) {
> +               rc = -ENOMEM;
> +               goto out;
> +       }
> +
> +       if (xen_feature(XENFEAT_auto_translated_physmap)) {
> +               struct page **pages;
> +               unsigned int i;
> +
> +               rc = alloc_empty_pages(vma, kdata.num);
> +               if (rc < 0)
> +                       goto out;
> +
> +               pages = vma->vm_private_data;
> +               for (i = 0; i < kdata.num; i++)
> +                       pfns[i] = page_to_pfn(pages[i]);
I don't think this is going to work well if the hypervisor is using a 
different granularity for the page.
Imagine Xen is using 4K but the kernel 64K. You would end up to have the 
resource not mapped contiguously in the memory.
Cheers,

--
Julien Grall

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel