> -----Original Message----- > From: Julien Grall [mailto:julien.gr...@arm.com] > Sent: 11 April 2018 10:46 > To: Paul Durrant <paul.durr...@citrix.com>; xen-de...@lists.xenproject.org; > linux-arm-ker...@lists.infradead.org; linux-kernel@vger.kernel.org > Cc: Juergen Gross <jgr...@suse.com>; Thomas Gleixner > <t...@linutronix.de>; Stefano Stabellini <sstabell...@kernel.org>; Ingo > Molnar <mi...@redhat.com> > Subject: Re: [PATCH v4] xen/privcmd: add > IOCTL_PRIVCMD_MMAP_RESOURCE > > 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.
Good point. I do need to take account of the kernel page size in this case. Paul > > Cheers, > > -- > Julien Grall
