RE: [PATCH v4] xen/privcmd: add IOCTL_PRIVCMD_MMAP_RESOURCE
> -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(, 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(>mmap_sem);
> > +
> > + vma = find_vma(mm, kdata.addr);
> > + if (!vma || vma->vm_ops != _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
RE: [PATCH v4] xen/privcmd: add IOCTL_PRIVCMD_MMAP_RESOURCE
> -Original Message-
> From: Julien Grall [mailto:julien.gr...@arm.com]
> Sent: 11 April 2018 10:46
> To: Paul Durrant ; xen-de...@lists.xenproject.org;
> linux-arm-ker...@lists.infradead.org; linux-kernel@vger.kernel.org
> Cc: Juergen Gross ; Thomas Gleixner
> ; Stefano Stabellini ; Ingo
> Molnar
> 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(, 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(>mmap_sem);
> > +
> > + vma = find_vma(mm, kdata.addr);
> > + if (!vma || vma->vm_ops != _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
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(, 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(>mmap_sem);
+
+ vma = find_vma(mm, kdata.addr);
+ if (!vma || vma->vm_ops != _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
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(, 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(>mmap_sem);
+
+ vma = find_vma(mm, kdata.addr);
+ if (!vma || vma->vm_ops != _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
