[PATCH V2 7/7]: PVH: privcmd changes.

[PATCH V2 7/7]: PVH: privcmd changes.

[Mukesh Rathor]

PVH: privcmd changes. PVH only supports the batch interface. To map a
foreign page to a process, pfn must be allocated. 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 R <mukesh.rathor@oracle.com>
---
 drivers/xen/privcmd.c |   70 +++++++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 68 insertions(+), 2 deletions(-)

diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
index 63d9ee8..b76d33c 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 +490,20 @@ static long privcmd_ioctl(struct file *file,
 	return ret;
 }
 
+static void privcmd_close(struct vm_area_struct *vma)
+{
+	struct page **pages = vma ? vma->vm_private_data : NULL;
+	int numpgs = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
+
+	if (!pages || !numpgs || !xen_feature(XENFEAT_auto_translated_physmap))
+		return;
+
+	xen_unmap_domain_mfn_range(vma);
+	while (numpgs--)
+		free_xenballooned_pages(1, &pages[numpgs]);
+	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 +514,7 @@ 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
 };
 
@@ -465,7 +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 = {
-- 
1.7.2.3

Re: [Xen-devel] [PATCH V2 7/7]: PVH: privcmd changes.

[Ian Campbell]

> @@ -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++];

Shame we can't pass the batchiness of mmap_batch_fn through to
remap_domain_mfn_range. Perhaps one for future work.

> +
>  	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;
> @@ -439,6 +490,20 @@ static long privcmd_ioctl(struct file *file,
>  	return ret;
>  }
>  
> +static void privcmd_close(struct vm_area_struct *vma)
> +{
> +	struct page **pages = vma ? vma->vm_private_data : NULL;
> +	int numpgs = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
> +
> +	if (!pages || !numpgs || !xen_feature(XENFEAT_auto_translated_physmap))
> +		return;
> +
> +	xen_unmap_domain_mfn_range(vma);
> +	while (numpgs--)
> +		free_xenballooned_pages(1, &pages[numpgs]);

Does free_xenballooned_pages(numpgs, pages) not do what I expect?

> +	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 +514,7 @@ 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
>  };
>  
> @@ -465,7 +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);

Looks good, thanks.

>  }
>  
>  const struct file_operations xen_privcmd_fops = {