[Xen-devel] [PATCH v6 5/5] xen: introduce XENMEM_pin

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

Introduce a new hypercall to allow a guest to pin one or more pages
whose machine addresses respect the number of bits addressable by the
caller as expressed by the address_bits field.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
---
 xen/common/memory.c         |   93 +++++++++++++++++++++++++++++++++++++++++++
 xen/include/public/memory.h |   33 +++++++++++++++
 2 files changed, 126 insertions(+), 0 deletions(-)

diff --git a/xen/common/memory.c b/xen/common/memory.c
index 31a85be..93171d0 100644
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -743,6 +743,95 @@ static int unpin(XEN_GUEST_HANDLE_PARAM(xen_unpin_t) arg)
     return rc;
 }
 
+static long pin(XEN_GUEST_HANDLE_PARAM(xen_pin_t) arg)
+{
+    int rc;
+    unsigned long i = 0, j;
+    struct xen_pin pin;
+    xen_pfn_t gpfn, mfn;
+    struct domain *d = NULL;
+    unsigned int memflags = 0;
+
+    if ( copy_from_guest(&pin, arg, 1) )
+        return -EFAULT;
+
+    /* Various sanity checks. */
+    if ( /* Extent orders are sensible? */
+         (pin.in.extent_order > MAX_ORDER) ||
+         /* Sizes of input list do not overflow a long? */
+         ((~0UL >> pin.in.extent_order) < pin.in.nr_extents) )
+    {
+        rc = -EFAULT;
+        goto fail;
+    }
+
+    if ( !guest_handle_okay(pin.in.extent_start, pin.in.nr_extents) )
+    {
+        rc = -EFAULT;
+        goto fail;
+    }
+
+    d = rcu_lock_domain_by_any_id(pin.in.domid);
+    if ( d == NULL )
+    {
+        rc = -ESRCH;
+        goto fail;
+    }
+
+    if ( !is_hardware_domain(d) )
+    {
+        rc = -EPERM;
+        goto fail;
+    }
+
+    memflags |= MEMF_bits(domain_clamp_alloc_bitsize(
+        d,
+        XENMEMF_get_address_bits(pin.in.mem_flags) ? :
+        (BITS_PER_LONG+PAGE_SHIFT)));
+
+    for ( ; i < pin.in.nr_extents; i++ )
+    {
+        if ( unlikely(__copy_from_guest_offset(
+                      &gpfn, pin.in.extent_start, i, 1)) )
+        {
+            rc = -EFAULT;
+            goto fail;
+        }
+
+        if ( generic_fls64(gpfn << PAGE_SHIFT) > memflags )
+        {
+            rc = -EINVAL;
+            goto fail;
+        }
+
+        rc = guest_physmap_pin_range(d, gpfn, pin.in.extent_order);
+        if ( rc )
+            goto fail;
+
+        for ( j = 0; j < (1UL << pin.in.extent_order); j++ )
+        {
+            mfn = gmfn_to_mfn(d, gpfn);
+            if ( __copy_to_guest_offset(pin.in.extent_start,
+                        (i << pin.in.extent_order) + j,
+                        &mfn, 1) )
+            {
+                rc = -EFAULT;
+                goto fail;
+            }
+        }
+    }
+
+    rc = 0;
+
+ fail:
+    pin.nr_pinned = i;
+    if ( __copy_field_to_guest(arg, &pin, nr_pinned) )
+        rc = -EFAULT;
+
+    rcu_unlock_domain(d);
+    return rc;
+}
+
 long do_memory_op(unsigned long cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
 {
     struct domain *d;
@@ -840,6 +929,10 @@ long do_memory_op(unsigned long cmd, 
XEN_GUEST_HANDLE_PARAM(void) arg)
         rc = unpin(guest_handle_cast(arg, xen_unpin_t));
         break;
 
+    case XENMEM_pin:
+        rc = pin(guest_handle_cast(arg, xen_pin_t));
+        break;
+
     case XENMEM_maximum_ram_page:
         rc = max_page;
         break;
diff --git a/xen/include/public/memory.h b/xen/include/public/memory.h
index 4accbd4..cbc0b9a 100644
--- a/xen/include/public/memory.h
+++ b/xen/include/public/memory.h
@@ -511,6 +511,39 @@ struct xen_unpin {
 typedef struct xen_unpin xen_unpin_t;
 DEFINE_XEN_GUEST_HANDLE(xen_unpin_t);
 
+/*
+ * XENMEM_pin pins a set of pages to make sure that the hypervisor does
+ * not change the p2m mappings for them.
+ *
+ */
+#define XENMEM_pin               28
+struct xen_pin {
+    /*
+     * [IN/OUT] Details of memory extents to be pinned (GMFN bases).
+     * Xen copies back the MFNs corresponding to the GMFNs passed in as
+     * argument.
+     * @in.address_bits contains the maximum number of bits addressable
+     * by the caller. If the machine addresses of the pages to be pinned
+     * are not addressable according to @in.address_bits, the hypercall
+     * fails and returns an errors. The pages are not pinned. Otherwise
+     * the hypercall succeeds.
+     */
+    struct xen_memory_reservation in;
+
+    /*
+     * [OUT] Number of input extents that were successfully pinned.
+     *  1. The first @nr_pinned input extents were successfully
+     *     pinned.
+     *  2. All other input extents are untouched.
+     *  3. If not all input extents are pinned then the return code of this
+     *     command will be non-zero.
+     */
+    xen_ulong_t nr_pinned;
+};
+typedef struct xen_pin xen_pin_t;
+DEFINE_XEN_GUEST_HANDLE(xen_pin_t);
+
+
 #endif /* defined(__XEN__) || defined(__XEN_TOOLS__) */
 
 #endif /* __XEN_PUBLIC_MEMORY_H__ */
-- 
1.7.2.5


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