xen/privcmd: add PRIVCMD_MMAPBATCH_V2 ioctl

PRIVCMD_MMAPBATCH_V2 extends PRIVCMD_MMAPBATCH with an additional
field for reporting the error code for every frame that could not be
mapped.  libxc prefers PRIVCMD_MMAPBATCH_V2 over PRIVCMD_MMAPBATCH.

Also expand PRIVCMD_MMAPBATCH to return appropriate error-encoding top nibble
in the mfn array.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Andres Lagar-Cavilla <andres@lagarcavilla.org>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
index 85226cbeca245caf6c71943e58226456b254727f..92a285b1b96af58d3e756ce53a1819c6eb5be86c 100644 (file)
--- a/drivers/xen/privcmd.c
+++ b/drivers/xen/privcmd.c
@@ -76,7 +76,7 @@ static void free_page_list(struct list_head *pages)
  */
 static int gather_array(struct list_head *pagelist,
                        unsigned nelem, size_t size,
-                       void __user *data)
+                       const void __user *data)
 {
        unsigned pageidx;
        void *pagedata;
@@ -246,61 +246,117 @@ struct mmap_batch_state {
        domid_t domain;
        unsigned long va;
        struct vm_area_struct *vma;
-       int err;
-
-       xen_pfn_t __user *user;
+       /* A tristate:
+        *      0 for no errors
+        *      1 if at least one error has happened (and no
+        *          -ENOENT errors have happened)
+        *      -ENOENT if at least 1 -ENOENT has happened.
+        */
+       int global_error;
+       /* An array for individual errors */
+       int *err;
+
+       /* User-space mfn array to store errors in the second pass for V1. */
+       xen_pfn_t __user *user_mfn;
 };
 
 static int mmap_batch_fn(void *data, void *state)
 {
        xen_pfn_t *mfnp = data;
        struct mmap_batch_state *st = state;
+       int ret;
 
-       if (xen_remap_domain_mfn_range(st->vma, st->va & PAGE_MASK, *mfnp, 1,
-                                      st->vma->vm_page_prot, st->domain) < 0) {
-               *mfnp |= 0xf0000000U;
-               st->err++;
+       ret = xen_remap_domain_mfn_range(st->vma, st->va & PAGE_MASK, *mfnp, 1,
+                                        st->vma->vm_page_prot, st->domain);
+
+       /* Store error code for second pass. */
+       *(st->err++) = ret;
+
+       /* And see if it affects the global_error. */
+       if (ret < 0) {
+               if (ret == -ENOENT)
+                       st->global_error = -ENOENT;
+               else {
+                       /* Record that at least one error has happened. */
+                       if (st->global_error == 0)
+                               st->global_error = 1;
+               }
        }
        st->va += PAGE_SIZE;
 
        return 0;
 }
 
-static int mmap_return_errors(void *data, void *state)
+static int mmap_return_errors_v1(void *data, void *state)
 {
        xen_pfn_t *mfnp = data;
        struct mmap_batch_state *st = state;
-
-       return put_user(*mfnp, st->user++);
+       int err = *(st->err++);
+
+       /*
+        * V1 encodes the error codes in the 32bit top nibble of the
+        * mfn (with its known limitations vis-a-vis 64 bit callers).
+        */
+       *mfnp |= (err == -ENOENT) ?
+                               PRIVCMD_MMAPBATCH_PAGED_ERROR :
+                               PRIVCMD_MMAPBATCH_MFN_ERROR;
+       return __put_user(*mfnp, st->user_mfn++);
 }
 
 static struct vm_operations_struct privcmd_vm_ops;
 
-static long privcmd_ioctl_mmap_batch(void __user *udata)
+static long privcmd_ioctl_mmap_batch(void __user *udata, int version)
 {
        int ret;
-       struct privcmd_mmapbatch m;
+       struct privcmd_mmapbatch_v2 m;
        struct mm_struct *mm = current->mm;
        struct vm_area_struct *vma;
        unsigned long nr_pages;
        LIST_HEAD(pagelist);
+       int *err_array = NULL;
        struct mmap_batch_state state;
 
        if (!xen_initial_domain())
                return -EPERM;
 
-       if (copy_from_user(&m, udata, sizeof(m)))
-               return -EFAULT;
+       switch (version) {
+       case 1:
+               if (copy_from_user(&m, udata, sizeof(struct privcmd_mmapbatch)))
+                       return -EFAULT;
+               /* Returns per-frame error in m.arr. */
+               m.err = NULL;
+               if (!access_ok(VERIFY_WRITE, m.arr, m.num * sizeof(*m.arr)))
+                       return -EFAULT;
+               break;
+       case 2:
+               if (copy_from_user(&m, udata, sizeof(struct privcmd_mmapbatch_v2)))
+                       return -EFAULT;
+               /* Returns per-frame error code in m.err. */
+               if (!access_ok(VERIFY_WRITE, m.err, m.num * (sizeof(*m.err))))
+                       return -EFAULT;
+               break;
+       default:
+               return -EINVAL;
+       }
 
        nr_pages = m.num;
        if ((m.num <= 0) || (nr_pages > (LONG_MAX >> PAGE_SHIFT)))
                return -EINVAL;
 
-       ret = gather_array(&pagelist, m.num, sizeof(xen_pfn_t),
-                          m.arr);
+       ret = gather_array(&pagelist, m.num, sizeof(xen_pfn_t), m.arr);
+
+       if (ret)
+               goto out;
+       if (list_empty(&pagelist)) {
+               ret = -EINVAL;
+               goto out;
+       }
 
-       if (ret || list_empty(&pagelist))
+       err_array = kcalloc(m.num, sizeof(int), GFP_KERNEL);
+       if (err_array == NULL) {
+               ret = -ENOMEM;
                goto out;
+       }
 
        down_write(&mm->mmap_sem);
 
@@ -315,24 +371,34 @@ static long privcmd_ioctl_mmap_batch(void __user *udata)
                goto out;
        }
 
-       state.domain = m.dom;
-       state.vma = vma;
-       state.va = m.addr;
-       state.err = 0;
+       state.domain        = m.dom;
+       state.vma           = vma;
+       state.va            = m.addr;
+       state.global_error  = 0;
+       state.err           = err_array;
 
-       ret = traverse_pages(m.num, sizeof(xen_pfn_t),
-                            &pagelist, mmap_batch_fn, &state);
+       /* mmap_batch_fn guarantees ret == 0 */
+       BUG_ON(traverse_pages(m.num, sizeof(xen_pfn_t),
+                            &pagelist, mmap_batch_fn, &state));
 
        up_write(&mm->mmap_sem);
 
-       if (state.err > 0) {
-               state.user = m.arr;
+       if (state.global_error && (version == 1)) {
+               /* Write back errors in second pass. */
+               state.user_mfn = (xen_pfn_t *)m.arr;
+               state.err      = err_array;
                ret = traverse_pages(m.num, sizeof(xen_pfn_t),
-                              &pagelist,
-                              mmap_return_errors, &state);
-       }
+                                    &pagelist, mmap_return_errors_v1, &state);
+       } else
+               ret = __copy_to_user(m.err, err_array, m.num * sizeof(int));
+
+       /* If we have not had any EFAULT-like global errors then set the global
+        * error to -ENOENT if necessary. */
+       if ((ret == 0) && (state.global_error == -ENOENT))
+               ret = -ENOENT;
 
 out:
+       kfree(err_array);
        free_page_list(&pagelist);
 
        return ret;
@@ -354,7 +420,11 @@ static long privcmd_ioctl(struct file *file,
                break;
 
        case IOCTL_PRIVCMD_MMAPBATCH:
-               ret = privcmd_ioctl_mmap_batch(udata);
+               ret = privcmd_ioctl_mmap_batch(udata, 1);
+               break;
+
+       case IOCTL_PRIVCMD_MMAPBATCH_V2:
+               ret = privcmd_ioctl_mmap_batch(udata, 2);
                break;
 
        default:

diff --git a/include/xen/privcmd.h b/include/xen/privcmd.h
index 45c1aa14b83db648eee1e142c3a941c3ce34de49..a85316811d79ad43493d21c1e35d51ed10aa257c 100644 (file)
--- a/include/xen/privcmd.h
+++ b/include/xen/privcmd.h
@@ -58,13 +58,33 @@ struct privcmd_mmapbatch {
        int num;     /* number of pages to populate */
        domid_t dom; /* target domain */
        __u64 addr;  /* virtual address */
-       xen_pfn_t __user *arr; /* array of mfns - top nibble set on err */
+       xen_pfn_t __user *arr; /* array of mfns - or'd with
+                                 PRIVCMD_MMAPBATCH_*_ERROR on err */
+};
+
+#define PRIVCMD_MMAPBATCH_MFN_ERROR     0xf0000000U
+#define PRIVCMD_MMAPBATCH_PAGED_ERROR   0x80000000U
+
+struct privcmd_mmapbatch_v2 {
+       unsigned int num; /* number of pages to populate */
+       domid_t dom;      /* target domain */
+       __u64 addr;       /* virtual address */
+       const xen_pfn_t __user *arr; /* array of mfns */
+       int __user *err;  /* array of error codes */
 };
 
 /*
  * @cmd: IOCTL_PRIVCMD_HYPERCALL
  * @arg: &privcmd_hypercall_t
  * Return: Value returned from execution of the specified hypercall.
+ *
+ * @cmd: IOCTL_PRIVCMD_MMAPBATCH_V2
+ * @arg: &struct privcmd_mmapbatch_v2
+ * Return: 0 on success (i.e., arg->err contains valid error codes for
+ * each frame).  On an error other than a failed frame remap, -1 is
+ * returned and errno is set to EINVAL, EFAULT etc.  As an exception,
+ * if the operation was otherwise successful but any frame failed with
+ * -ENOENT, then -1 is returned and errno is set to ENOENT.
  */
 #define IOCTL_PRIVCMD_HYPERCALL                                        \
        _IOC(_IOC_NONE, 'P', 0, sizeof(struct privcmd_hypercall))
@@ -72,5 +92,7 @@ struct privcmd_mmapbatch {
        _IOC(_IOC_NONE, 'P', 2, sizeof(struct privcmd_mmap))
 #define IOCTL_PRIVCMD_MMAPBATCH                                        \
        _IOC(_IOC_NONE, 'P', 3, sizeof(struct privcmd_mmapbatch))
+#define IOCTL_PRIVCMD_MMAPBATCH_V2                             \
+       _IOC(_IOC_NONE, 'P', 4, sizeof(struct privcmd_mmapbatch_v2))
 
 #endif /* __LINUX_PUBLIC_PRIVCMD_H__ */