[Xen-devel] [PATCH 6/6] xen/pvh: /dev/xen/privcmd changes.

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

From: Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>

PVH only supports the batch interface. To map a foreign page to a process,
the PFN must be allocated and PVH path uses ballooning for that purpose.

The returned PFN is then mapped to the foreign page.
xen_unmap_domain_mfn_range() is introduced to unmap these pages via the
privcmd close call.

Signed-off-by: Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>
[v1: Fix up privcmd_close]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 drivers/xen/privcmd.c |   69 +++++++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 67 insertions(+), 2 deletions(-)

diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
index b612267..b9d0898 100644
--- a/drivers/xen/privcmd.c
+++ b/drivers/xen/privcmd.c
@@ -33,11 +33,14 @@
 #include <xen/features.h>
 #include <xen/page.h>
 #include <xen/xen-ops.h>
+#include <xen/balloon.h>
 
 #include "privcmd.h"
 
 MODULE_LICENSE("GPL");
 
+#define PRIV_VMA_LOCKED ((void *)1)
+
 #ifndef HAVE_ARCH_PRIVCMD_MMAP
 static int privcmd_enforce_singleshot_mapping(struct vm_area_struct *vma);
 #endif
@@ -199,6 +202,10 @@ static long privcmd_ioctl_mmap(void __user *udata)
        if (!xen_initial_domain())
                return -EPERM;
 
+       /* We only support privcmd_ioctl_mmap_batch for auto translated. */
+       if (xen_feature(XENFEAT_auto_translated_physmap))
+               return -ENOSYS;
+
        if (copy_from_user(&mmapcmd, udata, sizeof(mmapcmd)))
                return -EFAULT;
 
@@ -246,6 +253,7 @@ struct mmap_batch_state {
        domid_t domain;
        unsigned long va;
        struct vm_area_struct *vma;
+       int index;
        /* A tristate:
         *      0 for no errors
         *      1 if at least one error has happened (and no
@@ -260,15 +268,24 @@ struct mmap_batch_state {
        xen_pfn_t __user *user_mfn;
 };
 
+/* auto translated dom0 note: if domU being created is PV, then mfn is
+ * mfn(addr on bus). If it's auto xlated, then mfn is pfn (input to HAP).
+ */
 static int mmap_batch_fn(void *data, void *state)
 {
        xen_pfn_t *mfnp = data;
        struct mmap_batch_state *st = state;
+       struct vm_area_struct *vma = st->vma;
+       struct page **pages = vma->vm_private_data;
+       struct page *cur_page = NULL;
        int ret;
 
+       if (xen_feature(XENFEAT_auto_translated_physmap))
+               cur_page = pages[st->index++];
+
        ret = xen_remap_domain_mfn_range(st->vma, st->va & PAGE_MASK, *mfnp, 1,
                                         st->vma->vm_page_prot, st->domain,
-                                        NULL);
+                                        &cur_page);
 
        /* Store error code for second pass. */
        *(st->err++) = ret;
@@ -304,6 +321,32 @@ static int mmap_return_errors_v1(void *data, void *state)
        return __put_user(*mfnp, st->user_mfn++);
 }
 
+/* Allocate pfns that are then mapped with gmfns from foreign domid. Update
+ * the vma with the page info to use later.
+ * Returns: 0 if success, otherwise -errno
+ */
+static int alloc_empty_pages(struct vm_area_struct *vma, int numpgs)
+{
+       int rc;
+       struct page **pages;
+
+       pages = kcalloc(numpgs, sizeof(pages[0]), GFP_KERNEL);
+       if (pages == NULL)
+               return -ENOMEM;
+
+       rc = alloc_xenballooned_pages(numpgs, pages, 0);
+       if (rc != 0) {
+               pr_warn("%s Could not alloc %d pfns rc:%d\n", __func__,
+                       numpgs, rc);
+               kfree(pages);
+               return -ENOMEM;
+       }
+       BUG_ON(vma->vm_private_data != PRIV_VMA_LOCKED);
+       vma->vm_private_data = pages;
+
+       return 0;
+}
+
 static struct vm_operations_struct privcmd_vm_ops;
 
 static long privcmd_ioctl_mmap_batch(void __user *udata, int version)
@@ -371,10 +414,18 @@ static long privcmd_ioctl_mmap_batch(void __user *udata, 
int version)
                up_write(&mm->mmap_sem);
                goto out;
        }
+       if (xen_feature(XENFEAT_auto_translated_physmap)) {
+               ret = alloc_empty_pages(vma, m.num);
+               if (ret < 0) {
+                       up_write(&mm->mmap_sem);
+                       goto out;
+               }
+       }
 
        state.domain        = m.dom;
        state.vma           = vma;
        state.va            = m.addr;
+       state.index         = 0;
        state.global_error  = 0;
        state.err           = err_array;
 
@@ -439,6 +490,19 @@ static long privcmd_ioctl(struct file *file,
        return ret;
 }
 
+static void privcmd_close(struct vm_area_struct *vma)
+{
+       struct page **pages = vma->vm_private_data;
+       int numpgs = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
+
+       if (!xen_feature(XENFEAT_auto_translated_physmap || !numpgs || !pages))
+               return;
+
+       xen_unmap_domain_mfn_range(vma, numpgs, pages);
+       free_xenballooned_pages(numpgs, pages);
+       kfree(pages);
+}
+
 static int privcmd_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 {
        printk(KERN_DEBUG "privcmd_fault: vma=%p %lx-%lx, pgoff=%lx, uv=%p\n",
@@ -449,6 +513,7 @@ static int privcmd_fault(struct vm_area_struct *vma, struct 
vm_fault *vmf)
 }
 
 static struct vm_operations_struct privcmd_vm_ops = {
+       .close = privcmd_close,
        .fault = privcmd_fault
 };
 
@@ -466,7 +531,7 @@ static int privcmd_mmap(struct file *file, struct 
vm_area_struct *vma)
 
 static int privcmd_enforce_singleshot_mapping(struct vm_area_struct *vma)
 {
-       return (xchg(&vma->vm_private_data, (void *)1) == NULL);
+       return !cmpxchg(&vma->vm_private_data, NULL, PRIV_VMA_LOCKED);
 }
 
 const struct file_operations xen_privcmd_fops = {
-- 
1.7.7.6


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