[Xen-devel] [PATCH v3 00/18] VM forking

[Xen-devel] [PATCH v3 00/18] VM forking

[Tamas K Lengyel]

The following series implements VM forking for Intel HVM guests to allow for
the fast creation of identical VMs without the assosciated high startup costs
of booting or restoring the VM from a savefile.

JIRA issue: https://xenproject.atlassian.net/browse/XEN-89

The main design goal with this series has been to reduce the time of creating
the VM fork as much as possible. To achieve this the VM forking process is
split into two steps:
    1) forking the VM on the hypervisor side;
    2) starting QEMU to handle the backed for emulated devices.

Step 1) involves creating a VM using the new "xl fork-vm" command. The
parent VM is expected to remain paused after forks are created from it (which
is different then what process forking normally entails). During this forking
operation the HVM context and VM settings are copied over to the new forked VM.
This operation is fast and it allows the forked VM to be unpaused and to be
monitored and accessed via VMI. Note however that without its device model
running (depending on what is executing in the VM) it is bound to
misbehave/crash when its trying to access devices that would be emulated by
QEMU. We anticipate that for certain use-cases this would be an acceptable
situation, in case for example when fuzzing is performed of code segments that
don't access such devices.

Step 2) involves launching QEMU to support the forked VM, which requires the
QEMU Xen savefile to be generated manually from the parent VM. This can be
accomplished simply by connecting to its QMP socket and issuing the
"xen-save-devices-state" command as documented by QEMU:
https://github.com/qemu/qemu/blob/master/docs/xen-save-devices-state.txt
Once the QEMU Xen savefile is generated the new "xl fork-launch-dm" command is
used to launch QEMU and load the specified savefile for it.

At runtime the forked VM starts running with an empty p2m which gets lazily
populated when the VM generates EPT faults, similar to how altp2m views are
populated. If the memory access is a read-only access, the p2m entry is
populated with a memory shared entry with its parent. For write memory accesses
or in case memory sharing wasn't possible (for example in case a reference is
held by a third party), a new page is allocated and the page contents are
copied over from the parent VM. Forks can be further forked if needed, thus
allowing for further memory savings.

A VM fork reset hypercall is also added that allows the fork to be reset to the
state it was just after a fork. This is an optimization for cases where the
forks are very short-lived and run without a device model, so resetting saves
some time compared to creating a brand new fork provided the fork has not
aquired a lot of memory. If the fork has a lot of memory deduplicated it is
likely going to be faster to create a new fork from scratch and destroying the
old one.

The series has been tested with both Linux and Windows VMs and functions as
expected. VM forking time has been measured to be 0.018s, device model launch
to be around 1s depending largely on the number of devices being emulated. Fork
resets have been measured to be 0.011s under the optimal circumstances.

Patches 1-2 implement changes to existing internal Xen APIs to make VM forking
possible.

Patches 3-14 are code-cleanups and adjustments of to Xen memory sharing
subsystem with no functional changes.

Patch 15 adds the hypervisor-side code implementing VM forking.

Patch 16 is integration of mem_access with forked VMs.

Patch 17 implements the VM fork reset operation hypervisor side bits.

Patch 18 adds the toolstack-side code implementing VM forking and reset.

Tamas K Lengyel (18):
  x86/hvm: introduce hvm_copy_context_and_params
  xen/x86: Make hap_get_allocation accessible
  x86/mem_sharing: make get_two_gfns take locks conditionally
  x86/mem_sharing: drop flags from mem_sharing_unshare_page
  x86/mem_sharing: don't try to unshare twice during page fault
  x86/mem_sharing: define mem_sharing_domain to hold some scattered
    variables
  x86/mem_sharing: Use INVALID_MFN and p2m_is_shared in
    relinquish_shared_pages
  x86/mem_sharing: Make add_to_physmap static and shorten name
  x86/mem_sharing: Convert MEM_SHARING_DESTROY_GFN to a bool
  x86/mem_sharing: Replace MEM_SHARING_DEBUG with gdprintk
  x86/mem_sharing: ASSERT that p2m_set_entry succeeds
  x86/mem_sharing: Enable mem_sharing on first memop
  x86/mem_sharing: Skip xen heap pages in memshr nominate
  x86/mem_sharing: check page type count earlier
  xen/mem_sharing: VM forking
  xen/mem_access: Use __get_gfn_type_access in set_mem_access
  x86/mem_sharing: reset a fork
  xen/tools: VM forking toolstack side

 tools/libxc/include/xenctrl.h     |  13 +
 tools/libxc/xc_memshr.c           |  22 ++
 tools/libxl/libxl.h               |   7 +
 tools/libxl/libxl_create.c        | 237 +++++++++-----
 tools/libxl/libxl_dm.c            |   2 +-
 tools/libxl/libxl_dom.c           |  83 +++--
 tools/libxl/libxl_internal.h      |   1 +
 tools/libxl/libxl_types.idl       |   1 +
 tools/xl/xl.h                     |   5 +
 tools/xl/xl_cmdtable.c            |  22 ++
 tools/xl/xl_saverestore.c         |  96 ++++++
 tools/xl/xl_vmcontrol.c           |   8 +
 xen/arch/x86/hvm/hvm.c            | 271 ++++++++++------
 xen/arch/x86/mm/hap/hap.c         |   3 +-
 xen/arch/x86/mm/mem_access.c      |   5 +-
 xen/arch/x86/mm/mem_sharing.c     | 502 +++++++++++++++++++++++-------
 xen/arch/x86/mm/p2m.c             |  16 +-
 xen/common/memory.c               |   2 +-
 xen/drivers/passthrough/pci.c     |   3 +-
 xen/include/asm-x86/hap.h         |   1 +
 xen/include/asm-x86/hvm/domain.h  |   6 +-
 xen/include/asm-x86/hvm/hvm.h     |   2 +
 xen/include/asm-x86/mem_sharing.h |  43 ++-
 xen/include/asm-x86/p2m.h         |  14 +-
 xen/include/public/memory.h       |   6 +
 xen/include/xen/sched.h           |   1 +
 26 files changed, 1033 insertions(+), 339 deletions(-)

-- 
2.20.1


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[Xen-devel] [PATCH v3 01/18] x86/hvm: introduce hvm_copy_context_and_params

[Tamas K Lengyel]

Currently the hvm parameters are only accessible via the HVMOP hypercalls. In
this patch we introduce a new function that can copy both the hvm context and
parameters directly into a target domain. We'll use this function during VM
forking operation.

There are no functional changes to hvmop_get/set_param, only adjustments to
make the code more accessible outside the HVMOP hypercalls.

Signed-off-by: Tamas K Lengyel <tamas.lengyel@intel.com>
---
 xen/arch/x86/hvm/hvm.c        | 241 +++++++++++++++++++++-------------
 xen/include/asm-x86/hvm/hvm.h |   2 +
 2 files changed, 152 insertions(+), 91 deletions(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 4723f5d09c..24f08d7043 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -4067,16 +4067,17 @@ static int hvmop_set_evtchn_upcall_vector(
 }
 
 static int hvm_allow_set_param(struct domain *d,
-                               const struct xen_hvm_param *a)
+                               uint32_t index,
+                               uint64_t new_value)
 {
-    uint64_t value = d->arch.hvm.params[a->index];
+    uint64_t value = d->arch.hvm.params[index];
     int rc;
 
     rc = xsm_hvm_param(XSM_TARGET, d, HVMOP_set_param);
     if ( rc )
         return rc;
 
-    switch ( a->index )
+    switch ( index )
     {
     /* The following parameters can be set by the guest. */
     case HVM_PARAM_CALLBACK_IRQ:
@@ -4109,7 +4110,7 @@ static int hvm_allow_set_param(struct domain *d,
     if ( rc )
         return rc;
 
-    switch ( a->index )
+    switch ( index )
     {
     /* The following parameters should only be changed once. */
     case HVM_PARAM_VIRIDIAN:
@@ -4119,7 +4120,7 @@ static int hvm_allow_set_param(struct domain *d,
     case HVM_PARAM_NR_IOREQ_SERVER_PAGES:
     case HVM_PARAM_ALTP2M:
     case HVM_PARAM_MCA_CAP:
-        if ( value != 0 && a->value != value )
+        if ( value != 0 && new_value != value )
             rc = -EEXIST;
         break;
     default:
@@ -4129,49 +4130,32 @@ static int hvm_allow_set_param(struct domain *d,
     return rc;
 }
 
-static int hvmop_set_param(
-    XEN_GUEST_HANDLE_PARAM(xen_hvm_param_t) arg)
+static int hvm_set_param(struct domain *d, uint32_t index, uint64_t value)
 {
     struct domain *curr_d = current->domain;
-    struct xen_hvm_param a;
-    struct domain *d;
-    struct vcpu *v;
     int rc;
+    struct vcpu *v;
 
-    if ( copy_from_guest(&a, arg, 1) )
-        return -EFAULT;
-
-    if ( a.index >= HVM_NR_PARAMS )
+    if ( index >= HVM_NR_PARAMS )
         return -EINVAL;
 
-    /* Make sure the above bound check is not bypassed during speculation. */
-    block_speculation();
-
-    d = rcu_lock_domain_by_any_id(a.domid);
-    if ( d == NULL )
-        return -ESRCH;
-
-    rc = -EINVAL;
-    if ( !is_hvm_domain(d) )
-        goto out;
-
-    rc = hvm_allow_set_param(d, &a);
+    rc = hvm_allow_set_param(d, index, value);
     if ( rc )
         goto out;
 
-    switch ( a.index )
+    switch ( index )
     {
     case HVM_PARAM_CALLBACK_IRQ:
-        hvm_set_callback_via(d, a.value);
+        hvm_set_callback_via(d, value);
         hvm_latch_shinfo_size(d);
         break;
     case HVM_PARAM_TIMER_MODE:
-        if ( a.value > HVMPTM_one_missed_tick_pending )
+        if ( value > HVMPTM_one_missed_tick_pending )
             rc = -EINVAL;
         break;
     case HVM_PARAM_VIRIDIAN:
-        if ( (a.value & ~HVMPV_feature_mask) ||
-             !(a.value & HVMPV_base_freq) )
+        if ( (value & ~HVMPV_feature_mask) ||
+             !(value & HVMPV_base_freq) )
             rc = -EINVAL;
         break;
     case HVM_PARAM_IDENT_PT:
@@ -4181,7 +4165,7 @@ static int hvmop_set_param(
          */
         if ( !paging_mode_hap(d) || !cpu_has_vmx )
         {
-            d->arch.hvm.params[a.index] = a.value;
+            d->arch.hvm.params[index] = value;
             break;
         }
 
@@ -4196,7 +4180,7 @@ static int hvmop_set_param(
 
         rc = 0;
         domain_pause(d);
-        d->arch.hvm.params[a.index] = a.value;
+        d->arch.hvm.params[index] = value;
         for_each_vcpu ( d, v )
             paging_update_cr3(v, false);
         domain_unpause(d);
@@ -4205,23 +4189,23 @@ static int hvmop_set_param(
         break;
     case HVM_PARAM_DM_DOMAIN:
         /* The only value this should ever be set to is DOMID_SELF */
-        if ( a.value != DOMID_SELF )
+        if ( value != DOMID_SELF )
             rc = -EINVAL;
 
-        a.value = curr_d->domain_id;
+        value = curr_d->domain_id;
         break;
     case HVM_PARAM_ACPI_S_STATE:
         rc = 0;
-        if ( a.value == 3 )
+        if ( value == 3 )
             hvm_s3_suspend(d);
-        else if ( a.value == 0 )
+        else if ( value == 0 )
             hvm_s3_resume(d);
         else
             rc = -EINVAL;
 
         break;
     case HVM_PARAM_ACPI_IOPORTS_LOCATION:
-        rc = pmtimer_change_ioport(d, a.value);
+        rc = pmtimer_change_ioport(d, value);
         break;
     case HVM_PARAM_MEMORY_EVENT_CR0:
     case HVM_PARAM_MEMORY_EVENT_CR3:
@@ -4236,24 +4220,24 @@ static int hvmop_set_param(
         rc = xsm_hvm_param_nested(XSM_PRIV, d);
         if ( rc )
             break;
-        if ( a.value > 1 )
+        if ( value > 1 )
             rc = -EINVAL;
         /*
          * Remove the check below once we have
          * shadow-on-shadow.
          */
-        if ( !paging_mode_hap(d) && a.value )
+        if ( !paging_mode_hap(d) && value )
             rc = -EINVAL;
-        if ( a.value &&
+        if ( value &&
              d->arch.hvm.params[HVM_PARAM_ALTP2M] )
             rc = -EINVAL;
         /* Set up NHVM state for any vcpus that are already up. */
-        if ( a.value &&
+        if ( value &&
              !d->arch.hvm.params[HVM_PARAM_NESTEDHVM] )
             for_each_vcpu(d, v)
                 if ( rc == 0 )
                     rc = nestedhvm_vcpu_initialise(v);
-        if ( !a.value || rc )
+        if ( !value || rc )
             for_each_vcpu(d, v)
                 nestedhvm_vcpu_destroy(v);
         break;
@@ -4261,30 +4245,30 @@ static int hvmop_set_param(
         rc = xsm_hvm_param_altp2mhvm(XSM_PRIV, d);
         if ( rc )
             break;
-        if ( a.value > XEN_ALTP2M_limited )
+        if ( value > XEN_ALTP2M_limited )
             rc = -EINVAL;
-        if ( a.value &&
+        if ( value &&
              d->arch.hvm.params[HVM_PARAM_NESTEDHVM] )
             rc = -EINVAL;
         break;
     case HVM_PARAM_TRIPLE_FAULT_REASON:
-        if ( a.value > SHUTDOWN_MAX )
+        if ( value > SHUTDOWN_MAX )
             rc = -EINVAL;
         break;
     case HVM_PARAM_IOREQ_SERVER_PFN:
-        d->arch.hvm.ioreq_gfn.base = a.value;
+        d->arch.hvm.ioreq_gfn.base = value;
         break;
     case HVM_PARAM_NR_IOREQ_SERVER_PAGES:
     {
         unsigned int i;
 
-        if ( a.value == 0 ||
-             a.value > sizeof(d->arch.hvm.ioreq_gfn.mask) * 8 )
+        if ( value == 0 ||
+             value > sizeof(d->arch.hvm.ioreq_gfn.mask) * 8 )
         {
             rc = -EINVAL;
             break;
         }
-        for ( i = 0; i < a.value; i++ )
+        for ( i = 0; i < value; i++ )
             set_bit(i, &d->arch.hvm.ioreq_gfn.mask);
 
         break;
@@ -4296,35 +4280,35 @@ static int hvmop_set_param(
                      sizeof(d->arch.hvm.ioreq_gfn.legacy_mask) * 8);
         BUILD_BUG_ON(HVM_PARAM_BUFIOREQ_PFN >
                      sizeof(d->arch.hvm.ioreq_gfn.legacy_mask) * 8);
-        if ( a.value )
-            set_bit(a.index, &d->arch.hvm.ioreq_gfn.legacy_mask);
+        if ( value )
+            set_bit(index, &d->arch.hvm.ioreq_gfn.legacy_mask);
         break;
 
     case HVM_PARAM_X87_FIP_WIDTH:
-        if ( a.value != 0 && a.value != 4 && a.value != 8 )
+        if ( value != 0 && value != 4 && value != 8 )
         {
             rc = -EINVAL;
             break;
         }
-        d->arch.x87_fip_width = a.value;
+        d->arch.x87_fip_width = value;
         break;
 
     case HVM_PARAM_VM86_TSS:
         /* Hardware would silently truncate high bits. */
-        if ( a.value != (uint32_t)a.value )
+        if ( value != (uint32_t)value )
         {
             if ( d == curr_d )
                 domain_crash(d);
             rc = -EINVAL;
         }
         /* Old hvmloader binaries hardcode the size to 128 bytes. */
-        if ( a.value )
-            a.value |= (128ULL << 32) | VM86_TSS_UPDATED;
-        a.index = HVM_PARAM_VM86_TSS_SIZED;
+        if ( value )
+            value |= (128ULL << 32) | VM86_TSS_UPDATED;
+        index = HVM_PARAM_VM86_TSS_SIZED;
         break;
 
     case HVM_PARAM_VM86_TSS_SIZED:
-        if ( (a.value >> 32) < sizeof(struct tss32) )
+        if ( (value >> 32) < sizeof(struct tss32) )
         {
             if ( d == curr_d )
                 domain_crash(d);
@@ -4335,26 +4319,56 @@ static int hvmop_set_param(
          * 256 bits interrupt redirection bitmap + 64k bits I/O bitmap
          * plus one padding byte).
          */
-        if ( (a.value >> 32) > sizeof(struct tss32) +
+        if ( (value >> 32) > sizeof(struct tss32) +
                                (0x100 / 8) + (0x10000 / 8) + 1 )
-            a.value = (uint32_t)a.value |
+            value = (uint32_t)value |
                       ((sizeof(struct tss32) + (0x100 / 8) +
                                                (0x10000 / 8) + 1) << 32);
-        a.value |= VM86_TSS_UPDATED;
+        value |= VM86_TSS_UPDATED;
         break;
 
     case HVM_PARAM_MCA_CAP:
-        rc = vmce_enable_mca_cap(d, a.value);
+        rc = vmce_enable_mca_cap(d, value);
         break;
     }
 
     if ( rc != 0 )
         goto out;
 
-    d->arch.hvm.params[a.index] = a.value;
+    d->arch.hvm.params[index] = value;
 
     HVM_DBG_LOG(DBG_LEVEL_HCALL, "set param %u = %"PRIx64,
-                a.index, a.value);
+                index, value);
+
+ out:
+    return rc;
+}
+
+int hvmop_set_param(
+    XEN_GUEST_HANDLE_PARAM(xen_hvm_param_t) arg)
+{
+    struct xen_hvm_param a;
+    struct domain *d;
+    int rc;
+
+    if ( copy_from_guest(&a, arg, 1) )
+        return -EFAULT;
+
+    if ( a.index >= HVM_NR_PARAMS )
+        return -EINVAL;
+
+    /* Make sure the above bound check is not bypassed during speculation. */
+    block_speculation();
+
+    d = rcu_lock_domain_by_any_id(a.domid);
+    if ( d == NULL )
+        return -ESRCH;
+
+    rc = -EINVAL;
+    if ( !is_hvm_domain(d) )
+        goto out;
+
+    rc = hvm_set_param(d, a.index, a.value);
 
  out:
     rcu_unlock_domain(d);
@@ -4362,7 +4376,7 @@ static int hvmop_set_param(
 }
 
 static int hvm_allow_get_param(struct domain *d,
-                               const struct xen_hvm_param *a)
+                               uint32_t index)
 {
     int rc;
 
@@ -4370,7 +4384,7 @@ static int hvm_allow_get_param(struct domain *d,
     if ( rc )
         return rc;
 
-    switch ( a->index )
+    switch ( index )
     {
     /* The following parameters can be read by the guest. */
     case HVM_PARAM_CALLBACK_IRQ:
@@ -4400,6 +4414,43 @@ static int hvm_allow_get_param(struct domain *d,
     return rc;
 }
 
+static int hvm_get_param(struct domain *d, uint32_t index, uint64_t *value)
+{
+    int rc;
+
+    if ( index >= HVM_NR_PARAMS || !value )
+        return -EINVAL;
+
+    rc = hvm_allow_get_param(d, index);
+    if ( rc )
+        return rc;
+
+    switch ( index )
+    {
+    case HVM_PARAM_ACPI_S_STATE:
+        *value = d->arch.hvm.is_s3_suspended ? 3 : 0;
+        break;
+
+    case HVM_PARAM_VM86_TSS:
+        *value = (uint32_t)d->arch.hvm.params[HVM_PARAM_VM86_TSS_SIZED];
+        break;
+
+    case HVM_PARAM_VM86_TSS_SIZED:
+        *value = d->arch.hvm.params[HVM_PARAM_VM86_TSS_SIZED] &
+                   ~VM86_TSS_UPDATED;
+        break;
+
+    case HVM_PARAM_X87_FIP_WIDTH:
+        *value = d->arch.x87_fip_width;
+        break;
+    default:
+        *value = d->arch.hvm.params[index];
+        break;
+    }
+
+    return 0;
+};
+
 static int hvmop_get_param(
     XEN_GUEST_HANDLE_PARAM(xen_hvm_param_t) arg)
 {
@@ -4424,33 +4475,10 @@ static int hvmop_get_param(
     if ( !is_hvm_domain(d) )
         goto out;
 
-    rc = hvm_allow_get_param(d, &a);
+    rc = hvm_get_param(d, a.index, &a.value);
     if ( rc )
         goto out;
 
-    switch ( a.index )
-    {
-    case HVM_PARAM_ACPI_S_STATE:
-        a.value = d->arch.hvm.is_s3_suspended ? 3 : 0;
-        break;
-
-    case HVM_PARAM_VM86_TSS:
-        a.value = (uint32_t)d->arch.hvm.params[HVM_PARAM_VM86_TSS_SIZED];
-        break;
-
-    case HVM_PARAM_VM86_TSS_SIZED:
-        a.value = d->arch.hvm.params[HVM_PARAM_VM86_TSS_SIZED] &
-                  ~VM86_TSS_UPDATED;
-        break;
-
-    case HVM_PARAM_X87_FIP_WIDTH:
-        a.value = d->arch.x87_fip_width;
-        break;
-    default:
-        a.value = d->arch.hvm.params[a.index];
-        break;
-    }
-
     rc = __copy_to_guest(arg, &a, 1) ? -EFAULT : 0;
 
     HVM_DBG_LOG(DBG_LEVEL_HCALL, "get param %u = %"PRIx64,
@@ -5266,6 +5294,37 @@ void hvm_set_segment_register(struct vcpu *v, enum x86_segment seg,
     alternative_vcall(hvm_funcs.set_segment_register, v, seg, reg);
 }
 
+int hvm_copy_context_and_params(struct domain *src, struct domain *dst)
+{
+    int rc, i;
+    struct hvm_domain_context c = { };
+
+    c.size = hvm_save_size(src);
+    if ( (c.data = xmalloc_bytes(c.size)) == NULL )
+        return -ENOMEM;
+
+    for ( i = 0; i < HVM_NR_PARAMS; i++ )
+    {
+        uint64_t value = 0;
+
+        if ( hvm_get_param(src, i, &value) || !value )
+            continue;
+
+        if ( (rc = hvm_set_param(dst, i, value)) )
+            goto out;
+    }
+
+    if ( (rc = hvm_save(src, &c)) )
+        goto out;
+
+    c.cur = 0;
+    rc = hvm_load(dst, &c);
+
+out:
+    xfree(c.data);
+    return rc;
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/xen/include/asm-x86/hvm/hvm.h b/xen/include/asm-x86/hvm/hvm.h
index 09793c12e9..6106b82c95 100644
--- a/xen/include/asm-x86/hvm/hvm.h
+++ b/xen/include/asm-x86/hvm/hvm.h
@@ -336,6 +336,8 @@ unsigned long hvm_cr4_guest_valid_bits(const struct domain *d, bool restore);
 bool hvm_flush_vcpu_tlb(bool (*flush_vcpu)(void *ctxt, struct vcpu *v),
                         void *ctxt);
 
+int hvm_copy_context_and_params(struct domain *src, struct domain *dst);
+
 #ifdef CONFIG_HVM
 
 #define hvm_get_guest_tsc(v) hvm_get_guest_tsc_fixed(v, 0)
-- 
2.20.1


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[Xen-devel] [PATCH v3 02/18] xen/x86: Make hap_get_allocation accessible

[Tamas K Lengyel]

During VM forking we'll copy the parent domain's parameters to the client,
including the HAP shadow memory setting that is used for storing the domain's
EPT. We'll copy this in the hypervisor instead doing it during toolstack launch
to allow the domain to start executing and unsharing memory before (or
even completely without) the toolstack.

Signed-off-by: Tamas K Lengyel <tamas.lengyel@intel.com>
---
 xen/arch/x86/mm/hap/hap.c | 3 +--
 xen/include/asm-x86/hap.h | 1 +
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/mm/hap/hap.c b/xen/arch/x86/mm/hap/hap.c
index 3d93f3451c..c7c7ff6e99 100644
--- a/xen/arch/x86/mm/hap/hap.c
+++ b/xen/arch/x86/mm/hap/hap.c
@@ -321,8 +321,7 @@ static void hap_free_p2m_page(struct domain *d, struct page_info *pg)
 }
 
 /* Return the size of the pool, rounded up to the nearest MB */
-static unsigned int
-hap_get_allocation(struct domain *d)
+unsigned int hap_get_allocation(struct domain *d)
 {
     unsigned int pg = d->arch.paging.hap.total_pages
         + d->arch.paging.hap.p2m_pages;
diff --git a/xen/include/asm-x86/hap.h b/xen/include/asm-x86/hap.h
index b94bfb4ed0..1bf07e49fe 100644
--- a/xen/include/asm-x86/hap.h
+++ b/xen/include/asm-x86/hap.h
@@ -45,6 +45,7 @@ int   hap_track_dirty_vram(struct domain *d,
 
 extern const struct paging_mode *hap_paging_get_mode(struct vcpu *);
 int hap_set_allocation(struct domain *d, unsigned int pages, bool *preempted);
+unsigned int hap_get_allocation(struct domain *d);
 
 #endif /* XEN_HAP_H */
 
-- 
2.20.1


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[Xen-devel] [PATCH v3 03/18] x86/mem_sharing: make get_two_gfns take locks conditionally

[Tamas K Lengyel]

During VM forking the client lock will already be taken.

Signed-off-by: Tamas K Lengyel <tamas.lengyel@intel.com>
Acked-by: Andrew Coopers <andrew.cooper3@citrix.com>
---
 xen/arch/x86/mm/mem_sharing.c | 11 ++++++-----
 xen/include/asm-x86/p2m.h     | 10 +++++-----
 2 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c
index ddf1f0f9f9..f6187403a0 100644
--- a/xen/arch/x86/mm/mem_sharing.c
+++ b/xen/arch/x86/mm/mem_sharing.c
@@ -955,7 +955,7 @@ static int share_pages(struct domain *sd, gfn_t sgfn, shr_handle_t sh,
     unsigned long put_count = 0;
 
     get_two_gfns(sd, sgfn, &smfn_type, NULL, &smfn,
-                 cd, cgfn, &cmfn_type, NULL, &cmfn, 0, &tg);
+                 cd, cgfn, &cmfn_type, NULL, &cmfn, 0, &tg, true);
 
     /*
      * This tricky business is to avoid two callers deadlocking if
@@ -1073,7 +1073,7 @@ err_out:
 }
 
 int mem_sharing_add_to_physmap(struct domain *sd, unsigned long sgfn, shr_handle_t sh,
-                               struct domain *cd, unsigned long cgfn)
+                               struct domain *cd, unsigned long cgfn, bool lock)
 {
     struct page_info *spage;
     int ret = -EINVAL;
@@ -1085,7 +1085,7 @@ int mem_sharing_add_to_physmap(struct domain *sd, unsigned long sgfn, shr_handle
     struct two_gfns tg;
 
     get_two_gfns(sd, _gfn(sgfn), &smfn_type, NULL, &smfn,
-                 cd, _gfn(cgfn), &cmfn_type, &a, &cmfn, 0, &tg);
+                 cd, _gfn(cgfn), &cmfn_type, &a, &cmfn, 0, &tg, lock);
 
     /* Get the source shared page, check and lock */
     ret = XENMEM_SHARING_OP_S_HANDLE_INVALID;
@@ -1162,7 +1162,8 @@ int mem_sharing_add_to_physmap(struct domain *sd, unsigned long sgfn, shr_handle
 err_unlock:
     mem_sharing_page_unlock(spage);
 err_out:
-    put_two_gfns(&tg);
+    if ( lock )
+        put_two_gfns(&tg);
     return ret;
 }
 
@@ -1583,7 +1584,7 @@ int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg)
         sh      = mso.u.share.source_handle;
         cgfn    = mso.u.share.client_gfn;
 
-        rc = mem_sharing_add_to_physmap(d, sgfn, sh, cd, cgfn);
+        rc = mem_sharing_add_to_physmap(d, sgfn, sh, cd, cgfn, true);
 
         rcu_unlock_domain(cd);
     }
diff --git a/xen/include/asm-x86/p2m.h b/xen/include/asm-x86/p2m.h
index 94285db1b4..7399c4a897 100644
--- a/xen/include/asm-x86/p2m.h
+++ b/xen/include/asm-x86/p2m.h
@@ -539,7 +539,7 @@ struct two_gfns {
 static inline void get_two_gfns(struct domain *rd, gfn_t rgfn,
         p2m_type_t *rt, p2m_access_t *ra, mfn_t *rmfn, struct domain *ld,
         gfn_t lgfn, p2m_type_t *lt, p2m_access_t *la, mfn_t *lmfn,
-        p2m_query_t q, struct two_gfns *rval)
+        p2m_query_t q, struct two_gfns *rval, bool lock)
 {
     mfn_t           *first_mfn, *second_mfn, scratch_mfn;
     p2m_access_t    *first_a, *second_a, scratch_a;
@@ -569,10 +569,10 @@ do {                                                    \
 #undef assign_pointers
 
     /* Now do the gets */
-    *first_mfn  = get_gfn_type_access(p2m_get_hostp2m(rval->first_domain),
-                                      gfn_x(rval->first_gfn), first_t, first_a, q, NULL);
-    *second_mfn = get_gfn_type_access(p2m_get_hostp2m(rval->second_domain),
-                                      gfn_x(rval->second_gfn), second_t, second_a, q, NULL);
+    *first_mfn  = __get_gfn_type_access(p2m_get_hostp2m(rval->first_domain),
+                                        gfn_x(rval->first_gfn), first_t, first_a, q, NULL, lock);
+    *second_mfn = __get_gfn_type_access(p2m_get_hostp2m(rval->second_domain),
+                                        gfn_x(rval->second_gfn), second_t, second_a, q, NULL, lock);
 }
 
 static inline void put_two_gfns(struct two_gfns *arg)
-- 
2.20.1


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[Xen-devel] [PATCH v3 04/18] x86/mem_sharing: drop flags from mem_sharing_unshare_page

[Tamas K Lengyel]

All callers pass 0 in.

Signed-off-by: Tamas K Lengyel <tamas.lengyel@intel.com>
Reviewed-by: Wei Liu <wl@xen.org>
---
 xen/arch/x86/hvm/hvm.c            | 2 +-
 xen/arch/x86/mm/p2m.c             | 5 ++---
 xen/common/memory.c               | 2 +-
 xen/include/asm-x86/mem_sharing.h | 8 +++-----
 4 files changed, 7 insertions(+), 10 deletions(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 24f08d7043..38e9006c92 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -1898,7 +1898,7 @@ int hvm_hap_nested_page_fault(paddr_t gpa, unsigned long gla,
     if ( npfec.write_access && (p2mt == p2m_ram_shared) )
     {
         ASSERT(p2m_is_hostp2m(p2m));
-        sharing_enomem = mem_sharing_unshare_page(currd, gfn, 0);
+        sharing_enomem = mem_sharing_unshare_page(currd, gfn);
         rc = 1;
         goto out_put_gfn;
     }
diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index 3119269073..baea632acc 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -515,7 +515,7 @@ mfn_t __get_gfn_type_access(struct p2m_domain *p2m, unsigned long gfn_l,
          * Try to unshare. If we fail, communicate ENOMEM without
          * sleeping.
          */
-        if ( mem_sharing_unshare_page(p2m->domain, gfn_l, 0) < 0 )
+        if ( mem_sharing_unshare_page(p2m->domain, gfn_l) < 0 )
             mem_sharing_notify_enomem(p2m->domain, gfn_l, false);
         mfn = p2m->get_entry(p2m, gfn, t, a, q, page_order, NULL);
     }
@@ -896,8 +896,7 @@ guest_physmap_add_entry(struct domain *d, gfn_t gfn, mfn_t mfn,
         {
             /* Do an unshare to cleanly take care of all corner cases. */
             int rc;
-            rc = mem_sharing_unshare_page(p2m->domain,
-                                          gfn_x(gfn_add(gfn, i)), 0);
+            rc = mem_sharing_unshare_page(p2m->domain, gfn_x(gfn_add(gfn, i)));
             if ( rc )
             {
                 p2m_unlock(p2m);
diff --git a/xen/common/memory.c b/xen/common/memory.c
index 309e872edf..c7d2bac452 100644
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -352,7 +352,7 @@ int guest_remove_page(struct domain *d, unsigned long gmfn)
          * might be the only one using this shared page, and we need to
          * trigger proper cleanup. Once done, this is like any other page.
          */
-        rc = mem_sharing_unshare_page(d, gmfn, 0);
+        rc = mem_sharing_unshare_page(d, gmfn);
         if ( rc )
         {
             mem_sharing_notify_enomem(d, gmfn, false);
diff --git a/xen/include/asm-x86/mem_sharing.h b/xen/include/asm-x86/mem_sharing.h
index af2a1038b5..cf7848709f 100644
--- a/xen/include/asm-x86/mem_sharing.h
+++ b/xen/include/asm-x86/mem_sharing.h
@@ -69,10 +69,9 @@ int __mem_sharing_unshare_page(struct domain *d,
                                uint16_t flags);
 
 static inline int mem_sharing_unshare_page(struct domain *d,
-                                           unsigned long gfn,
-                                           uint16_t flags)
+                                           unsigned long gfn)
 {
-    int rc = __mem_sharing_unshare_page(d, gfn, flags);
+    int rc = __mem_sharing_unshare_page(d, gfn, 0);
     BUG_ON(rc && (rc != -ENOMEM));
     return rc;
 }
@@ -115,8 +114,7 @@ static inline unsigned int mem_sharing_get_nr_shared_mfns(void)
     return 0;
 }
 
-static inline int mem_sharing_unshare_page(struct domain *d, unsigned long gfn,
-                                           uint16_t flags)
+static inline int mem_sharing_unshare_page(struct domain *d, unsigned long gfn)
 {
     ASSERT_UNREACHABLE();
     return -EOPNOTSUPP;
-- 
2.20.1


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[Xen-devel] [PATCH v3 05/18] x86/mem_sharing: don't try to unshare twice during page fault

[Tamas K Lengyel]

The page was already tried to be unshared in get_gfn_type_access. If that
didn't work, then trying again is pointless. Don't try to send vm_event again
either, simply check if there is a ring or not.

Signed-off-by: Tamas K Lengyel <tamas.lengyel@intel.com>
---
v3: use gprintk when the domain is going to crash
---
 xen/arch/x86/hvm/hvm.c | 28 ++++++++++++++++++----------
 1 file changed, 18 insertions(+), 10 deletions(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 38e9006c92..5d24ceb469 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -38,6 +38,7 @@
 #include <xen/warning.h>
 #include <xen/vpci.h>
 #include <xen/nospec.h>
+#include <xen/vm_event.h>
 #include <asm/shadow.h>
 #include <asm/hap.h>
 #include <asm/current.h>
@@ -1702,11 +1703,14 @@ int hvm_hap_nested_page_fault(paddr_t gpa, unsigned long gla,
     struct domain *currd = curr->domain;
     struct p2m_domain *p2m, *hostp2m;
     int rc, fall_through = 0, paged = 0;
-    int sharing_enomem = 0;
     vm_event_request_t *req_ptr = NULL;
     bool sync = false;
     unsigned int page_order;
 
+#ifdef CONFIG_MEM_SHARING
+    bool sharing_enomem = false;
+#endif
+
     /* On Nested Virtualization, walk the guest page table.
      * If this succeeds, all is fine.
      * If this fails, inject a nested page fault into the guest.
@@ -1894,14 +1898,16 @@ int hvm_hap_nested_page_fault(paddr_t gpa, unsigned long gla,
     if ( p2m_is_paged(p2mt) || (p2mt == p2m_ram_paging_out) )
         paged = 1;
 
-    /* Mem sharing: unshare the page and try again */
-    if ( npfec.write_access && (p2mt == p2m_ram_shared) )
+#ifdef CONFIG_MEM_SHARING
+    /* Mem sharing: if still shared on write access then its enomem */
+    if ( npfec.write_access && p2m_is_shared(p2mt) )
     {
         ASSERT(p2m_is_hostp2m(p2m));
-        sharing_enomem = mem_sharing_unshare_page(currd, gfn);
+        sharing_enomem = true;
         rc = 1;
         goto out_put_gfn;
     }
+#endif
 
     /* Spurious fault? PoD and log-dirty also take this path. */
     if ( p2m_is_ram(p2mt) )
@@ -1955,19 +1961,21 @@ int hvm_hap_nested_page_fault(paddr_t gpa, unsigned long gla,
      */
     if ( paged )
         p2m_mem_paging_populate(currd, gfn);
+
+#ifdef CONFIG_MEM_SHARING
     if ( sharing_enomem )
     {
-        int rv;
-
-        if ( (rv = mem_sharing_notify_enomem(currd, gfn, true)) < 0 )
+        if ( !vm_event_check_ring(currd->vm_event_share) )
         {
-            gdprintk(XENLOG_ERR, "Domain %hu attempt to unshare "
-                     "gfn %lx, ENOMEM and no helper (rc %d)\n",
-                     currd->domain_id, gfn, rv);
+            gprintk(XENLOG_ERR, "Domain %pd attempt to unshare "
+                    "gfn %lx, ENOMEM and no helper\n",
+                    currd, gfn);
             /* Crash the domain */
             rc = 0;
         }
     }
+#endif
+
     if ( req_ptr )
     {
         if ( monitor_traps(curr, sync, req_ptr) < 0 )
-- 
2.20.1


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[Xen-devel] [PATCH v3 06/18] x86/mem_sharing: define mem_sharing_domain to hold some scattered variables

[Tamas K Lengyel]

Create struct mem_sharing_domain under hvm_domain and move mem sharing
variables into it from p2m_domain and hvm_domain.

Expose the mem_sharing_enabled macro to be used consistently across Xen.

Remove some duplicate calls to mem_sharing_enabled in mem_sharing.c

Signed-off-by: Tamas K Lengyel <tamas.lengyel@intel.com>
---
 xen/arch/x86/mm/mem_sharing.c     | 10 ++++------
 xen/drivers/passthrough/pci.c     |  3 +--
 xen/include/asm-x86/hvm/domain.h  |  6 +++++-
 xen/include/asm-x86/mem_sharing.h | 16 ++++++++++++++++
 xen/include/asm-x86/p2m.h         |  4 ----
 5 files changed, 26 insertions(+), 13 deletions(-)

diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c
index f6187403a0..3aa61c30e6 100644
--- a/xen/arch/x86/mm/mem_sharing.c
+++ b/xen/arch/x86/mm/mem_sharing.c
@@ -197,9 +197,6 @@ static shr_handle_t get_next_handle(void)
     return x + 1;
 }
 
-#define mem_sharing_enabled(d) \
-    (is_hvm_domain(d) && (d)->arch.hvm.mem_sharing_enabled)
-
 static atomic_t nr_saved_mfns   = ATOMIC_INIT(0);
 static atomic_t nr_shared_mfns  = ATOMIC_INIT(0);
 
@@ -1309,6 +1306,7 @@ int __mem_sharing_unshare_page(struct domain *d,
 int relinquish_shared_pages(struct domain *d)
 {
     int rc = 0;
+    struct mem_sharing_domain *msd = &d->arch.hvm.mem_sharing;
     struct p2m_domain *p2m = p2m_get_hostp2m(d);
     unsigned long gfn, count = 0;
 
@@ -1316,7 +1314,7 @@ int relinquish_shared_pages(struct domain *d)
         return 0;
 
     p2m_lock(p2m);
-    for ( gfn = p2m->next_shared_gfn_to_relinquish;
+    for ( gfn = msd->next_shared_gfn_to_relinquish;
           gfn <= p2m->max_mapped_pfn; gfn++ )
     {
         p2m_access_t a;
@@ -1351,7 +1349,7 @@ int relinquish_shared_pages(struct domain *d)
         {
             if ( hypercall_preempt_check() )
             {
-                p2m->next_shared_gfn_to_relinquish = gfn + 1;
+                msd->next_shared_gfn_to_relinquish = gfn + 1;
                 rc = -ERESTART;
                 break;
             }
@@ -1437,7 +1435,7 @@ int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg)
 
     /* Only HAP is supported */
     rc = -ENODEV;
-    if ( !hap_enabled(d) || !d->arch.hvm.mem_sharing_enabled )
+    if ( !mem_sharing_enabled(d) )
         goto out;
 
     switch ( mso.op )
diff --git a/xen/drivers/passthrough/pci.c b/xen/drivers/passthrough/pci.c
index c07a63981a..65d1d457ff 100644
--- a/xen/drivers/passthrough/pci.c
+++ b/xen/drivers/passthrough/pci.c
@@ -1498,8 +1498,7 @@ static int assign_device(struct domain *d, u16 seg, u8 bus, u8 devfn, u32 flag)
     /* Prevent device assign if mem paging or mem sharing have been 
      * enabled for this domain */
     if ( d != dom_io &&
-         unlikely((is_hvm_domain(d) &&
-                   d->arch.hvm.mem_sharing_enabled) ||
+         unlikely(mem_sharing_enabled(d) ||
                   vm_event_check_ring(d->vm_event_paging) ||
                   p2m_get_hostp2m(d)->global_logdirty) )
         return -EXDEV;
diff --git a/xen/include/asm-x86/hvm/domain.h b/xen/include/asm-x86/hvm/domain.h
index bcc5621797..8f70ba2b1a 100644
--- a/xen/include/asm-x86/hvm/domain.h
+++ b/xen/include/asm-x86/hvm/domain.h
@@ -29,6 +29,7 @@
 #include <asm/hvm/viridian.h>
 #include <asm/hvm/vmx/vmcs.h>
 #include <asm/hvm/svm/vmcb.h>
+#include <asm/mem_sharing.h>
 #include <public/grant_table.h>
 #include <public/hvm/params.h>
 #include <public/hvm/save.h>
@@ -156,7 +157,6 @@ struct hvm_domain {
 
     struct viridian_domain *viridian;
 
-    bool_t                 mem_sharing_enabled;
     bool_t                 qemu_mapcache_invalidate;
     bool_t                 is_s3_suspended;
 
@@ -192,6 +192,10 @@ struct hvm_domain {
         struct vmx_domain vmx;
         struct svm_domain svm;
     };
+
+#ifdef CONFIG_MEM_SHARING
+    struct mem_sharing_domain mem_sharing;
+#endif
 };
 
 #endif /* __ASM_X86_HVM_DOMAIN_H__ */
diff --git a/xen/include/asm-x86/mem_sharing.h b/xen/include/asm-x86/mem_sharing.h
index cf7848709f..13114b6346 100644
--- a/xen/include/asm-x86/mem_sharing.h
+++ b/xen/include/asm-x86/mem_sharing.h
@@ -26,6 +26,20 @@
 
 #ifdef CONFIG_MEM_SHARING
 
+struct mem_sharing_domain
+{
+    bool enabled;
+
+    /*
+     * When releasing shared gfn's in a preemptible manner, recall where
+     * to resume the search.
+     */
+    unsigned long next_shared_gfn_to_relinquish;
+};
+
+#define mem_sharing_enabled(d) \
+    (hap_enabled(d) && (d)->arch.hvm.mem_sharing.enabled)
+
 /* Auditing of memory sharing code? */
 #ifndef NDEBUG
 #define MEM_SHARING_AUDIT 1
@@ -104,6 +118,8 @@ int relinquish_shared_pages(struct domain *d);
 
 #else
 
+#define mem_sharing_enabled(d) false
+
 static inline unsigned int mem_sharing_get_nr_saved_mfns(void)
 {
     return 0;
diff --git a/xen/include/asm-x86/p2m.h b/xen/include/asm-x86/p2m.h
index 7399c4a897..8defa90306 100644
--- a/xen/include/asm-x86/p2m.h
+++ b/xen/include/asm-x86/p2m.h
@@ -305,10 +305,6 @@ struct p2m_domain {
     unsigned long min_remapped_gfn;
     unsigned long max_remapped_gfn;
 
-    /* When releasing shared gfn's in a preemptible manner, recall where
-     * to resume the search */
-    unsigned long next_shared_gfn_to_relinquish;
-
 #ifdef CONFIG_HVM
     /* Populate-on-demand variables
      * All variables are protected with the pod lock. We cannot rely on
-- 
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[Xen-devel] [PATCH v3 07/18] x86/mem_sharing: Use INVALID_MFN and p2m_is_shared in relinquish_shared_pages

[Tamas K Lengyel]

While using _mfn(0) is of no consequence during teardown, INVALID_MFN is the
correct value that should be used.

Signed-off-by: Tamas K Lengyel <tamas.lengyel@intel.com>
---
 xen/arch/x86/mm/mem_sharing.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c
index 3aa61c30e6..95e75ff298 100644
--- a/xen/arch/x86/mm/mem_sharing.c
+++ b/xen/arch/x86/mm/mem_sharing.c
@@ -1326,7 +1326,7 @@ int relinquish_shared_pages(struct domain *d)
             break;
 
         mfn = p2m->get_entry(p2m, _gfn(gfn), &t, &a, 0, NULL, NULL);
-        if ( mfn_valid(mfn) && t == p2m_ram_shared )
+        if ( mfn_valid(mfn) && p2m_is_shared(t) )
         {
             /* Does not fail with ENOMEM given the DESTROY flag */
             BUG_ON(__mem_sharing_unshare_page(
@@ -1336,7 +1336,7 @@ int relinquish_shared_pages(struct domain *d)
              * unshare.  Must succeed: we just read the old entry and
              * we hold the p2m lock.
              */
-            set_rc = p2m->set_entry(p2m, _gfn(gfn), _mfn(0), PAGE_ORDER_4K,
+            set_rc = p2m->set_entry(p2m, _gfn(gfn), INVALID_MFN, PAGE_ORDER_4K,
                                     p2m_invalid, p2m_access_rwx, -1);
             ASSERT(!set_rc);
             count += 0x10;
-- 
2.20.1


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[Xen-devel] [PATCH v3 08/18] x86/mem_sharing: Make add_to_physmap static and shorten name

[Tamas K Lengyel]

It's not being called from outside mem_sharing.c

Signed-off-by: Tamas K Lengyel <tamas.lengyel@intel.com>
---
 xen/arch/x86/mm/mem_sharing.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c
index 95e75ff298..84b9f130b9 100644
--- a/xen/arch/x86/mm/mem_sharing.c
+++ b/xen/arch/x86/mm/mem_sharing.c
@@ -1069,8 +1069,9 @@ err_out:
     return ret;
 }
 
-int mem_sharing_add_to_physmap(struct domain *sd, unsigned long sgfn, shr_handle_t sh,
-                               struct domain *cd, unsigned long cgfn, bool lock)
+static
+int add_to_physmap(struct domain *sd, unsigned long sgfn, shr_handle_t sh,
+                   struct domain *cd, unsigned long cgfn, bool lock)
 {
     struct page_info *spage;
     int ret = -EINVAL;
@@ -1582,7 +1583,7 @@ int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg)
         sh      = mso.u.share.source_handle;
         cgfn    = mso.u.share.client_gfn;
 
-        rc = mem_sharing_add_to_physmap(d, sgfn, sh, cd, cgfn, true);
+        rc = add_to_physmap(d, sgfn, sh, cd, cgfn, true);
 
         rcu_unlock_domain(cd);
     }
-- 
2.20.1


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[Xen-devel] [PATCH v3 09/18] x86/mem_sharing: Convert MEM_SHARING_DESTROY_GFN to a bool

[Tamas K Lengyel]

MEM_SHARING_DESTROY_GFN is used on the 'flags' bitfield during unsharing.
However, the bitfield is not used for anything else, so just convert it to a
bool instead.

Signed-off-by: Tamas K Lengyel <tamas.lengyel@intel.com>
---
 xen/arch/x86/mm/mem_sharing.c     | 9 ++++-----
 xen/include/asm-x86/mem_sharing.h | 5 ++---
 2 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c
index 84b9f130b9..0435a7f803 100644
--- a/xen/arch/x86/mm/mem_sharing.c
+++ b/xen/arch/x86/mm/mem_sharing.c
@@ -1182,7 +1182,7 @@ err_out:
  */
 int __mem_sharing_unshare_page(struct domain *d,
                                unsigned long gfn,
-                               uint16_t flags)
+                               bool destroy)
 {
     p2m_type_t p2mt;
     mfn_t mfn;
@@ -1238,7 +1238,7 @@ int __mem_sharing_unshare_page(struct domain *d,
      * If the GFN is getting destroyed drop the references to MFN
      * (possibly freeing the page), and exit early.
      */
-    if ( flags & MEM_SHARING_DESTROY_GFN )
+    if ( destroy )
     {
         if ( !last_gfn )
             mem_sharing_gfn_destroy(page, d, gfn_info);
@@ -1329,9 +1329,8 @@ int relinquish_shared_pages(struct domain *d)
         mfn = p2m->get_entry(p2m, _gfn(gfn), &t, &a, 0, NULL, NULL);
         if ( mfn_valid(mfn) && p2m_is_shared(t) )
         {
-            /* Does not fail with ENOMEM given the DESTROY flag */
-            BUG_ON(__mem_sharing_unshare_page(
-                       d, gfn, MEM_SHARING_DESTROY_GFN));
+            /* Does not fail with ENOMEM given "destroy" is set to true */
+            BUG_ON(__mem_sharing_unshare_page(d, gfn, true));
             /*
              * Clear out the p2m entry so no one else may try to
              * unshare.  Must succeed: we just read the old entry and
diff --git a/xen/include/asm-x86/mem_sharing.h b/xen/include/asm-x86/mem_sharing.h
index 13114b6346..c915fd973f 100644
--- a/xen/include/asm-x86/mem_sharing.h
+++ b/xen/include/asm-x86/mem_sharing.h
@@ -76,16 +76,15 @@ struct page_sharing_info
 unsigned int mem_sharing_get_nr_saved_mfns(void);
 unsigned int mem_sharing_get_nr_shared_mfns(void);
 
-#define MEM_SHARING_DESTROY_GFN       (1<<1)
 /* Only fails with -ENOMEM. Enforce it with a BUG_ON wrapper. */
 int __mem_sharing_unshare_page(struct domain *d,
                                unsigned long gfn,
-                               uint16_t flags);
+                               bool destroy);
 
 static inline int mem_sharing_unshare_page(struct domain *d,
                                            unsigned long gfn)
 {
-    int rc = __mem_sharing_unshare_page(d, gfn, 0);
+    int rc = __mem_sharing_unshare_page(d, gfn, false);
     BUG_ON(rc && (rc != -ENOMEM));
     return rc;
 }
-- 
2.20.1


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[Xen-devel] [PATCH v3 10/18] x86/mem_sharing: Replace MEM_SHARING_DEBUG with gdprintk

[Tamas K Lengyel]

Using XENLOG_ERR level since this is only used in debug paths (ie. it's
expected the user already has loglvl=all set).

Signed-off-by: Tamas K Lengyel <tamas.lengyel@intel.com>
---
 xen/arch/x86/mm/mem_sharing.c | 86 +++++++++++++++++------------------
 1 file changed, 43 insertions(+), 43 deletions(-)

diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c
index 0435a7f803..93e7605900 100644
--- a/xen/arch/x86/mm/mem_sharing.c
+++ b/xen/arch/x86/mm/mem_sharing.c
@@ -49,9 +49,6 @@ typedef struct pg_lock_data {
 
 static DEFINE_PER_CPU(pg_lock_data_t, __pld);
 
-#define MEM_SHARING_DEBUG(_f, _a...)                                  \
-    debugtrace_printk("mem_sharing_debug: %s(): " _f, __func__, ##_a)
-
 /* Reverse map defines */
 #define RMAP_HASHTAB_ORDER  0
 #define RMAP_HASHTAB_SIZE   \
@@ -494,19 +491,19 @@ static int audit(void)
         /* If we can't lock it, it's definitely not a shared page */
         if ( !mem_sharing_page_lock(pg) )
         {
-            MEM_SHARING_DEBUG(
-                "mfn %lx in audit list, but cannot be locked (%lx)!\n",
-                mfn_x(mfn), pg->u.inuse.type_info);
-            errors++;
-            continue;
+            gdprintk(XENLOG_ERR,
+                     "mfn %lx in audit list, but cannot be locked (%lx)!\n",
+                     mfn_x(mfn), pg->u.inuse.type_info);
+           errors++;
+           continue;
         }
 
         /* Check if the MFN has correct type, owner and handle. */
         if ( (pg->u.inuse.type_info & PGT_type_mask) != PGT_shared_page )
         {
-            MEM_SHARING_DEBUG(
-                "mfn %lx in audit list, but not PGT_shared_page (%lx)!\n",
-                mfn_x(mfn), pg->u.inuse.type_info & PGT_type_mask);
+            gdprintk(XENLOG_ERR,
+                     "mfn %lx in audit list, but not PGT_shared_page (%lx)!\n",
+                     mfn_x(mfn), pg->u.inuse.type_info & PGT_type_mask);
             errors++;
             continue;
         }
@@ -514,24 +511,24 @@ static int audit(void)
         /* Check the page owner. */
         if ( page_get_owner(pg) != dom_cow )
         {
-            MEM_SHARING_DEBUG("mfn %lx shared, but wrong owner %pd!\n",
-                              mfn_x(mfn), page_get_owner(pg));
-            errors++;
+               gdprintk(XENLOG_ERR, "mfn %lx shared, but wrong owner (%hu)!\n",
+                        mfn_x(mfn), page_get_owner(pg)->domain_id);
+               errors++;
         }
 
         /* Check the m2p entry */
         if ( !SHARED_M2P(get_gpfn_from_mfn(mfn_x(mfn))) )
         {
-            MEM_SHARING_DEBUG("mfn %lx shared, but wrong m2p entry (%lx)!\n",
-                              mfn_x(mfn), get_gpfn_from_mfn(mfn_x(mfn)));
-            errors++;
+               gdprintk(XENLOG_ERR, "mfn %lx shared, but wrong m2p entry (%lx)!\n",
+                        mfn_x(mfn), get_gpfn_from_mfn(mfn_x(mfn)));
+               errors++;
         }
 
         /* Check we have a list */
         if ( (!pg->sharing) || !rmap_has_entries(pg) )
         {
-            MEM_SHARING_DEBUG("mfn %lx shared, but empty gfn list!\n",
-                              mfn_x(mfn));
+            gdprintk(XENLOG_ERR, "mfn %lx shared, but empty gfn list!\n",
+                     mfn_x(mfn));
             errors++;
             continue;
         }
@@ -550,24 +547,26 @@ static int audit(void)
             d = get_domain_by_id(g->domain);
             if ( d == NULL )
             {
-                MEM_SHARING_DEBUG("Unknown dom: %hu, for PFN=%lx, MFN=%lx\n",
-                                  g->domain, g->gfn, mfn_x(mfn));
+                gdprintk(XENLOG_ERR,
+                         "Unknown dom: %hu, for PFN=%lx, MFN=%lx\n",
+                         g->domain, g->gfn, mfn_x(mfn));
                 errors++;
                 continue;
             }
             o_mfn = get_gfn_query_unlocked(d, g->gfn, &t);
             if ( !mfn_eq(o_mfn, mfn) )
             {
-                MEM_SHARING_DEBUG("Incorrect P2M for d=%hu, PFN=%lx."
-                                  "Expecting MFN=%lx, got %lx\n",
-                                  g->domain, g->gfn, mfn_x(mfn), mfn_x(o_mfn));
+                gdprintk(XENLOG_ERR, "Incorrect P2M for d=%hu, PFN=%lx."
+                         "Expecting MFN=%lx, got %lx\n",
+                         g->domain, g->gfn, mfn_x(mfn), mfn_x(o_mfn));
                 errors++;
             }
             if ( t != p2m_ram_shared )
             {
-                MEM_SHARING_DEBUG("Incorrect P2M type for d=%hu, PFN=%lx MFN=%lx."
-                                  "Expecting t=%d, got %d\n",
-                                  g->domain, g->gfn, mfn_x(mfn), p2m_ram_shared, t);
+                gdprintk(XENLOG_ERR,
+                         "Incorrect P2M type for d=%hu, PFN=%lx MFN=%lx."
+                         "Expecting t=%d, got %d\n",
+                         g->domain, g->gfn, mfn_x(mfn), p2m_ram_shared, t);
                 errors++;
             }
             put_domain(d);
@@ -576,10 +575,10 @@ static int audit(void)
         /* The type count has an extra ref because we have locked the page */
         if ( (nr_gfns + 1) != (pg->u.inuse.type_info & PGT_count_mask) )
         {
-            MEM_SHARING_DEBUG("Mismatched counts for MFN=%lx."
-                              "nr_gfns in list %lu, in type_info %lx\n",
-                              mfn_x(mfn), nr_gfns,
-                              (pg->u.inuse.type_info & PGT_count_mask));
+            gdprintk(XENLOG_ERR, "Mismatched counts for MFN=%lx."
+                     "nr_gfns in list %lu, in type_info %lx\n",
+                     mfn_x(mfn), nr_gfns,
+                     (pg->u.inuse.type_info & PGT_count_mask));
             errors++;
         }
 
@@ -590,8 +589,8 @@ static int audit(void)
 
     if ( count_found != count_expected )
     {
-        MEM_SHARING_DEBUG("Expected %ld shared mfns, found %ld.",
-                          count_expected, count_found);
+        gdprintk(XENLOG_ERR, "Expected %ld shared mfns, found %ld.",
+                 count_expected, count_found);
         errors++;
     }
 
@@ -769,10 +768,10 @@ static int debug_mfn(mfn_t mfn)
         return -EINVAL;
     }
 
-    MEM_SHARING_DEBUG(
-        "Debug page: MFN=%lx is ci=%lx, ti=%lx, owner=%pd\n",
-        mfn_x(page_to_mfn(page)), page->count_info,
-        page->u.inuse.type_info, page_get_owner(page));
+    gdprintk(XENLOG_ERR,
+             "Debug page: MFN=%lx is ci=%lx, ti=%lx, owner_id=%d\n",
+             mfn_x(page_to_mfn(page)), page->count_info,
+             page->u.inuse.type_info, page_get_owner(page)->domain_id);
 
     /* -1 because the page is locked and that's an additional type ref */
     num_refs = ((int) (page->u.inuse.type_info & PGT_count_mask)) - 1;
@@ -788,8 +787,9 @@ static int debug_gfn(struct domain *d, gfn_t gfn)
 
     mfn = get_gfn_query(d, gfn_x(gfn), &p2mt);
 
-    MEM_SHARING_DEBUG("Debug for dom%d, gfn=%" PRI_gfn "\n",
-                      d->domain_id, gfn_x(gfn));
+    gdprintk(XENLOG_ERR, "Debug for dom%d, gfn=%" PRI_gfn "\n",
+             d->domain_id, gfn_x(gfn));
+
     num_refs = debug_mfn(mfn);
     put_gfn(d, gfn_x(gfn));
 
@@ -805,13 +805,13 @@ static int debug_gref(struct domain *d, grant_ref_t ref)
     rc = mem_sharing_gref_to_gfn(d->grant_table, ref, &gfn, &status);
     if ( rc )
     {
-        MEM_SHARING_DEBUG("Asked to debug [dom=%d,gref=%u]: error %d.\n",
-                          d->domain_id, ref, rc);
+        gdprintk(XENLOG_ERR, "Asked to debug [dom=%d,gref=%u]: error %d.\n",
+                 d->domain_id, ref, rc);
         return rc;
     }
 
-    MEM_SHARING_DEBUG("==> Grant [dom=%d,ref=%d], status=%x. ",
-                      d->domain_id, ref, status);
+    gdprintk(XENLOG_ERR, "==> Grant [dom=%d,ref=%d], status=%x. ",
+             d->domain_id, ref, status);
 
     return debug_gfn(d, gfn);
 }
-- 
2.20.1


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[Xen-devel] [PATCH v3 11/18] x86/mem_sharing: ASSERT that p2m_set_entry succeeds

[Tamas K Lengyel]

Signed-off-by: Tamas K Lengyel <tamas.lengyel@intel.com>
---
 xen/arch/x86/mm/mem_sharing.c | 42 +++++++++++++++++------------------
 1 file changed, 21 insertions(+), 21 deletions(-)

diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c
index 93e7605900..3f36cd6bbc 100644
--- a/xen/arch/x86/mm/mem_sharing.c
+++ b/xen/arch/x86/mm/mem_sharing.c
@@ -1117,11 +1117,19 @@ int add_to_physmap(struct domain *sd, unsigned long sgfn, shr_handle_t sh,
         goto err_unlock;
     }
 
+    /*
+     * Must succeed, we just read the entry and hold the p2m lock
+     * via get_two_gfns.
+     */
     ret = p2m_set_entry(p2m, _gfn(cgfn), smfn, PAGE_ORDER_4K,
                         p2m_ram_shared, a);
+    ASSERT(!ret);
 
-    /* Tempted to turn this into an assert */
-    if ( ret )
+    /*
+     * There is a chance we're plugging a hole where a paged out
+     * page was.
+     */
+    if ( p2m_is_paging(cmfn_type) && (cmfn_type != p2m_ram_paging_out) )
     {
         mem_sharing_gfn_destroy(spage, cd, gfn_info);
         put_page_and_type(spage);
@@ -1129,29 +1137,21 @@ int add_to_physmap(struct domain *sd, unsigned long sgfn, shr_handle_t sh,
     else
     {
         /*
-         * There is a chance we're plugging a hole where a paged out
-         * page was.
+         * Further, there is a chance this was a valid page.
+         * Don't leak it.
          */
-        if ( p2m_is_paging(cmfn_type) && (cmfn_type != p2m_ram_paging_out) )
+        if ( mfn_valid(cmfn) )
         {
-            atomic_dec(&cd->paged_pages);
-            /*
-             * Further, there is a chance this was a valid page.
-             * Don't leak it.
-             */
-            if ( mfn_valid(cmfn) )
+            struct page_info *cpage = mfn_to_page(cmfn);
+
+            if ( !get_page(cpage, cd) )
             {
-                struct page_info *cpage = mfn_to_page(cmfn);
-
-                if ( !get_page(cpage, cd) )
-                {
-                    domain_crash(cd);
-                    ret = -EOVERFLOW;
-                    goto err_unlock;
-                }
-                put_page_alloc_ref(cpage);
-                put_page(cpage);
+                domain_crash(cd);
+                ret = -EOVERFLOW;
+                goto err_unlock;
             }
+            put_page_alloc_ref(cpage);
+            put_page(cpage);
         }
     }
 
-- 
2.20.1


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[Xen-devel] [PATCH v3 12/18] x86/mem_sharing: Enable mem_sharing on first memop

[Tamas K Lengyel]

It is wasteful to require separate hypercalls to enable sharing on both the
parent and the client domain during VM forking. To speed things up we enable
sharing on the first memop in case it wasn't already enabled.

Signed-off-by: Tamas K Lengyel <tamas.lengyel@intel.com>
---
 xen/arch/x86/mm/mem_sharing.c | 36 +++++++++++++++++++++--------------
 1 file changed, 22 insertions(+), 14 deletions(-)

diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c
index 3f36cd6bbc..b8a9228ecf 100644
--- a/xen/arch/x86/mm/mem_sharing.c
+++ b/xen/arch/x86/mm/mem_sharing.c
@@ -1412,6 +1412,24 @@ static int range_share(struct domain *d, struct domain *cd,
     return rc;
 }
 
+static inline int mem_sharing_control(struct domain *d, bool enable)
+{
+    if ( enable )
+    {
+        if ( unlikely(!is_hvm_domain(d)) )
+            return -ENOSYS;
+
+        if ( unlikely(!hap_enabled(d)) )
+            return -ENODEV;
+
+        if ( unlikely(is_iommu_enabled(d)) )
+            return -EXDEV;
+    }
+
+    d->arch.hvm.mem_sharing.enabled = enable;
+    return 0;
+}
+
 int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg)
 {
     int rc;
@@ -1433,10 +1451,8 @@ int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg)
     if ( rc )
         goto out;
 
-    /* Only HAP is supported */
-    rc = -ENODEV;
-    if ( !mem_sharing_enabled(d) )
-        goto out;
+    if ( !mem_sharing_enabled(d) && (rc = mem_sharing_control(d, true)) )
+        return rc;
 
     switch ( mso.op )
     {
@@ -1703,18 +1719,10 @@ int mem_sharing_domctl(struct domain *d, struct xen_domctl_mem_sharing_op *mec)
 {
     int rc;
 
-    /* Only HAP is supported */
-    if ( !hap_enabled(d) )
-        return -ENODEV;
-
-    switch ( mec->op )
+    switch( mec->op )
     {
     case XEN_DOMCTL_MEM_SHARING_CONTROL:
-        rc = 0;
-        if ( unlikely(is_iommu_enabled(d) && mec->u.enable) )
-            rc = -EXDEV;
-        else
-            d->arch.hvm.mem_sharing_enabled = mec->u.enable;
+        rc = mem_sharing_control(d, mec->u.enable);
         break;
 
     default:
-- 
2.20.1


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[Xen-devel] [PATCH v3 13/18] x86/mem_sharing: Skip xen heap pages in memshr nominate

[Tamas K Lengyel]

Trying to share these would fail anyway, better to skip them early.

Signed-off-by: Tamas K Lengyel <tamas.lengyel@intel.com>
---
 xen/arch/x86/mm/mem_sharing.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c
index b8a9228ecf..baa3e35ded 100644
--- a/xen/arch/x86/mm/mem_sharing.c
+++ b/xen/arch/x86/mm/mem_sharing.c
@@ -852,6 +852,11 @@ static int nominate_page(struct domain *d, gfn_t gfn,
     if ( !p2m_is_sharable(p2mt) )
         goto out;
 
+    /* Skip xen heap pages */
+    page = mfn_to_page(mfn);
+    if ( !page || is_xen_heap_page(page) )
+        goto out;
+
     /* Check if there are mem_access/remapped altp2m entries for this page */
     if ( altp2m_active(d) )
     {
@@ -882,7 +887,6 @@ static int nominate_page(struct domain *d, gfn_t gfn,
     }
 
     /* Try to convert the mfn to the sharable type */
-    page = mfn_to_page(mfn);
     ret = page_make_sharable(d, page, expected_refcnt);
     if ( ret )
         goto out;
-- 
2.20.1


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[Xen-devel] [PATCH v3 14/18] x86/mem_sharing: check page type count earlier

[Tamas K Lengyel]

Signed-off-by: Tamas K Lengyel <tamas.lengyel@intel.com>
---
 xen/arch/x86/mm/mem_sharing.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c
index baa3e35ded..ecbe40545d 100644
--- a/xen/arch/x86/mm/mem_sharing.c
+++ b/xen/arch/x86/mm/mem_sharing.c
@@ -652,19 +652,18 @@ static int page_make_sharable(struct domain *d,
         return -EBUSY;
     }
 
-    /* Change page type and count atomically */
-    if ( !get_page_and_type(page, d, PGT_shared_page) )
+    /* Check if page is already typed and bail early if it is */
+    if ( (page->u.inuse.type_info & PGT_count_mask) != 1 )
     {
         spin_unlock(&d->page_alloc_lock);
-        return -EINVAL;
+        return -EEXIST;
     }
 
-    /* Check it wasn't already sharable and undo if it was */
-    if ( (page->u.inuse.type_info & PGT_count_mask) != 1 )
+    /* Change page type and count atomically */
+    if ( !get_page_and_type(page, d, PGT_shared_page) )
     {
         spin_unlock(&d->page_alloc_lock);
-        put_page_and_type(page);
-        return -EEXIST;
+        return -EINVAL;
     }
 
     /*
-- 
2.20.1


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[Xen-devel] [PATCH v3 15/18] xen/mem_sharing: VM forking

[Tamas K Lengyel]

VM forking is the process of creating a domain with an empty memory space and a
parent domain specified from which to populate the memory when necessary. For
the new domain to be functional the VM state is copied over as part of the fork
operation (HVM params, hap allocation, etc).

Signed-off-by: Tamas K Lengyel <tamas.lengyel@intel.com>
---
 xen/arch/x86/hvm/hvm.c            |   2 +-
 xen/arch/x86/mm/mem_sharing.c     | 204 ++++++++++++++++++++++++++++++
 xen/arch/x86/mm/p2m.c             |  11 +-
 xen/include/asm-x86/mem_sharing.h |  20 ++-
 xen/include/public/memory.h       |   5 +
 xen/include/xen/sched.h           |   1 +
 6 files changed, 239 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 5d24ceb469..3241e2a5ac 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -1909,7 +1909,7 @@ int hvm_hap_nested_page_fault(paddr_t gpa, unsigned long gla,
     }
 #endif
 
-    /* Spurious fault? PoD and log-dirty also take this path. */
+    /* Spurious fault? PoD, log-dirty and VM forking also take this path. */
     if ( p2m_is_ram(p2mt) )
     {
         rc = 1;
diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c
index ecbe40545d..d544801681 100644
--- a/xen/arch/x86/mm/mem_sharing.c
+++ b/xen/arch/x86/mm/mem_sharing.c
@@ -22,11 +22,13 @@
 
 #include <xen/types.h>
 #include <xen/domain_page.h>
+#include <xen/event.h>
 #include <xen/spinlock.h>
 #include <xen/rwlock.h>
 #include <xen/mm.h>
 #include <xen/grant_table.h>
 #include <xen/sched.h>
+#include <xen/sched-if.h>
 #include <xen/rcupdate.h>
 #include <xen/guest_access.h>
 #include <xen/vm_event.h>
@@ -36,6 +38,9 @@
 #include <asm/altp2m.h>
 #include <asm/atomic.h>
 #include <asm/event.h>
+#include <asm/hap.h>
+#include <asm/hvm/hvm.h>
+#include <asm/hvm/save.h>
 #include <xsm/xsm.h>
 
 #include "mm-locks.h"
@@ -1433,6 +1438,175 @@ static inline int mem_sharing_control(struct domain *d, bool enable)
     return 0;
 }
 
+/*
+ * Forking a page only gets called when the VM faults due to no entry being
+ * in the EPT for the access. Depending on the type of access we either
+ * populate the physmap with a shared entry for read-only access or
+ * fork the page if its a write access.
+ *
+ * The client p2m is already locked so we only need to lock
+ * the parent's here.
+ */
+int mem_sharing_fork_page(struct domain *d, gfn_t gfn, bool unsharing)
+{
+    int rc = -ENOENT;
+    shr_handle_t handle;
+    struct domain *parent;
+    struct p2m_domain *p2m;
+    unsigned long gfn_l = gfn_x(gfn);
+    mfn_t mfn, new_mfn;
+    p2m_type_t p2mt;
+    struct page_info *page;
+
+    if ( !mem_sharing_is_fork(d) )
+        return -ENOENT;
+
+    parent = d->parent;
+
+    if ( !unsharing )
+    {
+        /* For read-only accesses we just add a shared entry to the physmap */
+        while ( parent )
+        {
+            if ( !(rc = nominate_page(parent, gfn, 0, &handle)) )
+                break;
+
+            parent = parent->parent;
+        }
+
+        if ( !rc )
+        {
+            /* The client's p2m is already locked */
+            struct p2m_domain *pp2m = p2m_get_hostp2m(parent);
+
+            p2m_lock(pp2m);
+            rc = add_to_physmap(parent, gfn_l, handle, d, gfn_l, false);
+            p2m_unlock(pp2m);
+
+            if ( !rc )
+                return 0;
+        }
+    }
+
+    /*
+     * If it's a write access (ie. unsharing) or if adding a shared entry to
+     * the physmap failed we'll fork the page directly.
+     */
+    p2m = p2m_get_hostp2m(d);
+    parent = d->parent;
+
+    while ( parent )
+    {
+        mfn = get_gfn_query(parent, gfn_l, &p2mt);
+
+        if ( mfn_valid(mfn) && p2m_is_any_ram(p2mt) )
+            break;
+
+        put_gfn(parent, gfn_l);
+        parent = parent->parent;
+    }
+
+    if ( !parent )
+        return -ENOENT;
+
+    if ( !(page = alloc_domheap_page(d, 0)) )
+    {
+        put_gfn(parent, gfn_l);
+        return -ENOMEM;
+    }
+
+    new_mfn = page_to_mfn(page);
+    copy_domain_page(new_mfn, mfn);
+    set_gpfn_from_mfn(mfn_x(new_mfn), gfn_l);
+
+    put_gfn(parent, gfn_l);
+
+    return p2m->set_entry(p2m, gfn, new_mfn, PAGE_ORDER_4K, p2m_ram_rw,
+                          p2m->default_access, -1);
+}
+
+static int bring_up_vcpus(struct domain *cd, struct cpupool *cpupool)
+{
+    int ret;
+    unsigned int i;
+
+    if ( (ret = cpupool_move_domain(cd, cpupool)) )
+        return ret;
+
+    for ( i = 0; i < cd->max_vcpus; i++ )
+    {
+        if ( cd->vcpu[i] )
+            continue;
+
+        if ( !vcpu_create(cd, i) )
+            return -EINVAL;
+    }
+
+    domain_update_node_affinity(cd);
+    return 0;
+}
+
+static int fork_hap_allocation(struct domain *d, struct domain *cd)
+{
+    int rc;
+    bool preempted;
+    unsigned long mb = hap_get_allocation(d);
+
+    if ( mb == hap_get_allocation(cd) )
+        return 0;
+
+    paging_lock(cd);
+    rc = hap_set_allocation(cd, mb << (20 - PAGE_SHIFT), &preempted);
+    paging_unlock(cd);
+
+    if ( rc )
+        return rc;
+
+    if ( preempted )
+        return -ERESTART;
+
+    return 0;
+}
+
+static void fork_tsc(struct domain *d, struct domain *cd)
+{
+    uint32_t tsc_mode;
+    uint32_t gtsc_khz;
+    uint32_t incarnation;
+    uint64_t elapsed_nsec;
+
+    tsc_get_info(d, &tsc_mode, &elapsed_nsec, &gtsc_khz, &incarnation);
+    tsc_set_info(cd, tsc_mode, elapsed_nsec, gtsc_khz, incarnation);
+}
+
+static int mem_sharing_fork(struct domain *d, struct domain *cd)
+{
+    int rc;
+
+    if ( !d->controller_pause_count &&
+         (rc = domain_pause_by_systemcontroller(d)) )
+        return rc;
+
+    cd->max_pages = d->max_pages;
+    cd->max_vcpus = d->max_vcpus;
+
+    /* this is preemptible so it's the first to get done */
+    if ( (rc = fork_hap_allocation(d, cd)) )
+        return rc;
+
+    if ( (rc = bring_up_vcpus(cd, d->cpupool)) )
+        return rc;
+
+    if ( (rc = hvm_copy_context_and_params(d, cd)) )
+        return rc;
+
+    fork_tsc(d, cd);
+
+    cd->parent = d;
+
+    return 0;
+}
+
 int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg)
 {
     int rc;
@@ -1705,6 +1879,36 @@ int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg)
         rc = debug_gref(d, mso.u.debug.u.gref);
         break;
 
+    case XENMEM_sharing_op_fork:
+    {
+        struct domain *pd;
+
+        rc = -EINVAL;
+        if ( mso.u.fork._pad[0] || mso.u.fork._pad[1] ||
+             mso.u.fork._pad[2] )
+            goto out;
+
+        rc = rcu_lock_live_remote_domain_by_id(mso.u.fork.parent_domain,
+                                               &pd);
+        if ( rc )
+            goto out;
+
+        if ( !mem_sharing_enabled(pd) )
+        {
+            if ( (rc = mem_sharing_control(pd, true)) )
+                goto out;
+        }
+
+        rc = mem_sharing_fork(pd, d);
+
+        if ( rc == -ERESTART )
+            rc = hypercall_create_continuation(__HYPERVISOR_memory_op,
+                                               "lh", XENMEM_sharing_op,
+                                               arg);
+        rcu_unlock_domain(pd);
+        break;
+    }
+
     default:
         rc = -ENOSYS;
         break;
diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index baea632acc..81f7679ec1 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -508,6 +508,14 @@ mfn_t __get_gfn_type_access(struct p2m_domain *p2m, unsigned long gfn_l,
 
     mfn = p2m->get_entry(p2m, gfn, t, a, q, page_order, NULL);
 
+    /* Check if we need to fork the page */
+    if ( (q & P2M_ALLOC) && p2m_is_hole(*t) &&
+         !mem_sharing_fork_page(p2m->domain, gfn, !!(q & P2M_UNSHARE)) )
+    {
+        mfn = p2m->get_entry(p2m, gfn, t, a, q, page_order, NULL);
+    }
+
+    /* Check if we need to unshare the page */
     if ( (q & P2M_UNSHARE) && p2m_is_shared(*t) )
     {
         ASSERT(p2m_is_hostp2m(p2m));
@@ -585,7 +593,8 @@ struct page_info *p2m_get_page_from_gfn(
             return page;
 
         /* Error path: not a suitable GFN at all */
-        if ( !p2m_is_ram(*t) && !p2m_is_paging(*t) && !p2m_is_pod(*t) )
+        if ( !p2m_is_ram(*t) && !p2m_is_paging(*t) && !p2m_is_pod(*t) &&
+             !mem_sharing_is_fork(p2m->domain) )
             return NULL;
     }
 
diff --git a/xen/include/asm-x86/mem_sharing.h b/xen/include/asm-x86/mem_sharing.h
index c915fd973f..f1f785296f 100644
--- a/xen/include/asm-x86/mem_sharing.h
+++ b/xen/include/asm-x86/mem_sharing.h
@@ -26,8 +26,7 @@
 
 #ifdef CONFIG_MEM_SHARING
 
-struct mem_sharing_domain
-{
+struct mem_sharing_domain {
     bool enabled;
 
     /*
@@ -40,6 +39,9 @@ struct mem_sharing_domain
 #define mem_sharing_enabled(d) \
     (hap_enabled(d) && (d)->arch.hvm.mem_sharing.enabled)
 
+#define mem_sharing_is_fork(d) \
+    (mem_sharing_enabled(d) && !!((d)->parent))
+
 /* Auditing of memory sharing code? */
 #ifndef NDEBUG
 #define MEM_SHARING_AUDIT 1
@@ -89,6 +91,9 @@ static inline int mem_sharing_unshare_page(struct domain *d,
     return rc;
 }
 
+int mem_sharing_fork_page(struct domain *d, gfn_t gfn,
+                          bool unsharing);
+
 /*
  * If called by a foreign domain, possible errors are
  *   -EBUSY -> ring full
@@ -118,6 +123,7 @@ int relinquish_shared_pages(struct domain *d);
 #else
 
 #define mem_sharing_enabled(d) false
+#define mem_sharing_is_fork(p2m) false
 
 static inline unsigned int mem_sharing_get_nr_saved_mfns(void)
 {
@@ -142,6 +148,16 @@ static inline int mem_sharing_notify_enomem(struct domain *d, unsigned long gfn,
     return -EOPNOTSUPP;
 }
 
+static inline int mem_sharing_fork(struct domain *d, struct domain *cd, bool vcpu)
+{
+    return -EOPNOTSUPP;
+}
+
+static inline int mem_sharing_fork_page(struct domain *d, gfn_t gfn, bool lock)
+{
+    return -EOPNOTSUPP;
+}
+
 #endif
 
 #endif /* __MEM_SHARING_H__ */
diff --git a/xen/include/public/memory.h b/xen/include/public/memory.h
index cfdda6e2a8..90a3f4498e 100644
--- a/xen/include/public/memory.h
+++ b/xen/include/public/memory.h
@@ -482,6 +482,7 @@ DEFINE_XEN_GUEST_HANDLE(xen_mem_access_op_t);
 #define XENMEM_sharing_op_add_physmap       6
 #define XENMEM_sharing_op_audit             7
 #define XENMEM_sharing_op_range_share       8
+#define XENMEM_sharing_op_fork              9
 
 #define XENMEM_SHARING_OP_S_HANDLE_INVALID  (-10)
 #define XENMEM_SHARING_OP_C_HANDLE_INVALID  (-9)
@@ -532,6 +533,10 @@ struct xen_mem_sharing_op {
                 uint32_t gref;     /* IN: gref to debug         */
             } u;
         } debug;
+        struct mem_sharing_op_fork {
+            domid_t parent_domain;
+            uint16_t _pad[3];                /* Must be set to 0 */
+        } fork;
     } u;
 };
 typedef struct xen_mem_sharing_op xen_mem_sharing_op_t;
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 94add37990..cd112b8858 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -504,6 +504,7 @@ struct domain
     /* Memory sharing support */
 #ifdef CONFIG_MEM_SHARING
     struct vm_event_domain *vm_event_share;
+    struct domain *parent; /* VM fork parent */
 #endif
     /* Memory paging support */
 #ifdef CONFIG_HAS_MEM_PAGING
-- 
2.20.1


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[Xen-devel] [PATCH v3 16/18] xen/mem_access: Use __get_gfn_type_access in set_mem_access

[Tamas K Lengyel]

Use __get_gfn_type_access instead of p2m->get_entry to trigger page-forking
when the mem_access permission is being set on a page that has not yet been
copied over from the parent.

Signed-off-by: Tamas K Lengyel <tamas.lengyel@intel.com>
---
 xen/arch/x86/mm/mem_access.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/mm/mem_access.c b/xen/arch/x86/mm/mem_access.c
index 320b9fe621..9caf08a5b2 100644
--- a/xen/arch/x86/mm/mem_access.c
+++ b/xen/arch/x86/mm/mem_access.c
@@ -303,11 +303,10 @@ static int set_mem_access(struct domain *d, struct p2m_domain *p2m,
     ASSERT(!ap2m);
 #endif
     {
-        mfn_t mfn;
         p2m_access_t _a;
         p2m_type_t t;
-
-        mfn = p2m->get_entry(p2m, gfn, &t, &_a, 0, NULL, NULL);
+        mfn_t mfn = __get_gfn_type_access(p2m, gfn_x(gfn), &t, &_a,
+                                          P2M_ALLOC, NULL, false);
         rc = p2m->set_entry(p2m, gfn, mfn, PAGE_ORDER_4K, t, a, -1);
     }
 
-- 
2.20.1


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[Xen-devel] [PATCH v3 17/18] x86/mem_sharing: reset a fork

[Tamas K Lengyel]

Implement hypercall that allows a fork to shed all memory that got allocated
for it during its execution and re-load its vCPU context from the parent VM.
This allows the forked VM to reset into the same state the parent VM is in a
faster way then creating a new fork would be. Measurements show about a 2x
speedup during normal fuzzing operations. Performance may vary depending how
much memory got allocated for the forked VM. If it has been completely
deduplicated from the parent VM then creating a new fork would likely be more
performant.

Signed-off-by: Tamas K Lengyel <tamas.lengyel@intel.com>
---
v3: use page_list_for_each_safe so we don't have to loop twice
    add comments explaining the lack of hypercall continuation
    only remove pages doing reset that are of sharable type
---
 xen/arch/x86/mm/mem_sharing.c | 80 +++++++++++++++++++++++++++++++++++
 xen/include/public/memory.h   |  1 +
 2 files changed, 81 insertions(+)

diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c
index d544801681..f16570b01b 100644
--- a/xen/arch/x86/mm/mem_sharing.c
+++ b/xen/arch/x86/mm/mem_sharing.c
@@ -1607,6 +1607,63 @@ static int mem_sharing_fork(struct domain *d, struct domain *cd)
     return 0;
 }
 
+/*
+ * The fork reset operation is intended to be used on short-lived forks only.
+ * There is no hypercall continuation operation implemented for this reason.
+ * For forks that obtain a larger memory footprint it is likely going to be
+ * more performant to create a new fork instead of resetting an existing one.
+ *
+ * TODO: In case this hypercall would become useful on forks with larger memory
+ * footprints the hypercall continuation should be implemented.
+ */
+static int mem_sharing_fork_reset(struct domain *d, struct domain *cd)
+{
+    int rc;
+    struct p2m_domain* p2m = p2m_get_hostp2m(cd);
+    struct page_info *page, *tmp;
+
+    if ( !d->controller_pause_count &&
+         (rc = domain_pause_by_systemcontroller(d)) )
+        return rc;
+
+    page_list_for_each_safe(page, tmp, &cd->page_list)
+    {
+        p2m_type_t p2mt;
+        p2m_access_t p2ma;
+        gfn_t gfn;
+        mfn_t mfn = page_to_mfn(page);
+
+        if ( !mfn_valid(mfn) )
+            continue;
+
+        gfn = mfn_to_gfn(cd, mfn);
+        mfn = __get_gfn_type_access(p2m, gfn_x(gfn), &p2mt, &p2ma,
+                                    0, NULL, false);
+
+        /* only remove pages that can be re-populated using sharing */
+        if ( !p2m_is_sharable(p2mt) )
+            continue;
+
+        /* take an extra reference */
+        if ( !get_page(page, cd) )
+            continue;
+
+        rc = p2m->set_entry(p2m, gfn, INVALID_MFN, PAGE_ORDER_4K,
+                            p2m_invalid, p2m_access_rwx, -1);
+        ASSERT(!rc);
+
+        put_page_alloc_ref(page);
+        put_page(page);
+    }
+
+    if ( (rc = hvm_copy_context_and_params(d, cd)) )
+        return rc;
+
+    fork_tsc(d, cd);
+
+    return 0;
+}
+
 int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg)
 {
     int rc;
@@ -1909,6 +1966,29 @@ int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg)
         break;
     }
 
+    case XENMEM_sharing_op_fork_reset:
+    {
+        struct domain *pd;
+
+        rc = -EINVAL;
+        if ( mso.u.fork._pad[0] || mso.u.fork._pad[1] ||
+             mso.u.fork._pad[2] )
+            goto out;
+
+        rc = -ENOSYS;
+        if ( !d->parent )
+            goto out;
+
+        rc = rcu_lock_live_remote_domain_by_id(d->parent->domain_id, &pd);
+        if ( rc )
+            goto out;
+
+        rc = mem_sharing_fork_reset(pd, d);
+
+        rcu_unlock_domain(pd);
+        break;
+    }
+
     default:
         rc = -ENOSYS;
         break;
diff --git a/xen/include/public/memory.h b/xen/include/public/memory.h
index 90a3f4498e..e3d063e22e 100644
--- a/xen/include/public/memory.h
+++ b/xen/include/public/memory.h
@@ -483,6 +483,7 @@ DEFINE_XEN_GUEST_HANDLE(xen_mem_access_op_t);
 #define XENMEM_sharing_op_audit             7
 #define XENMEM_sharing_op_range_share       8
 #define XENMEM_sharing_op_fork              9
+#define XENMEM_sharing_op_fork_reset        10
 
 #define XENMEM_SHARING_OP_S_HANDLE_INVALID  (-10)
 #define XENMEM_SHARING_OP_C_HANDLE_INVALID  (-9)
-- 
2.20.1


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[Xen-devel] [PATCH v3 18/18] xen/tools: VM forking toolstack side

[Tamas K Lengyel]

Add necessary bits to implement "xl fork-vm", "xl fork-launch-dm" and
"xl fork-reset" commands. The process is split in two to allow tools needing
access to the new VM as fast as possible after it was forked. It is expected
that under certain use-cases the second command that launches QEMU will be
skipped entirely.

Signed-off-by: Tamas K Lengyel <tamas.lengyel@intel.com>
---
 tools/libxc/include/xenctrl.h |  13 ++
 tools/libxc/xc_memshr.c       |  22 ++++
 tools/libxl/libxl.h           |   7 +
 tools/libxl/libxl_create.c    | 237 +++++++++++++++++++++++-----------
 tools/libxl/libxl_dm.c        |   2 +-
 tools/libxl/libxl_dom.c       |  83 ++++++++----
 tools/libxl/libxl_internal.h  |   1 +
 tools/libxl/libxl_types.idl   |   1 +
 tools/xl/xl.h                 |   5 +
 tools/xl/xl_cmdtable.c        |  22 ++++
 tools/xl/xl_saverestore.c     |  96 ++++++++++++++
 tools/xl/xl_vmcontrol.c       |   8 ++
 12 files changed, 393 insertions(+), 104 deletions(-)

diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
index 75f191ae3a..ffb0bb9a42 100644
--- a/tools/libxc/include/xenctrl.h
+++ b/tools/libxc/include/xenctrl.h
@@ -2221,6 +2221,19 @@ int xc_memshr_range_share(xc_interface *xch,
                           uint64_t first_gfn,
                           uint64_t last_gfn);
 
+int xc_memshr_fork(xc_interface *xch,
+                   uint32_t source_domain,
+                   uint32_t client_domain);
+
+/*
+ * Note: this function is only intended to be used on short-lived forks that
+ * haven't yet aquired a lot of memory. In case the fork has a lot of memory
+ * it is likely more performant to create a new fork with xc_memshr_fork.
+ *
+ * With VMs that have a lot of memory this call may block for a long time.
+ */
+int xc_memshr_fork_reset(xc_interface *xch, uint32_t forked_domain);
+
 /* Debug calls: return the number of pages referencing the shared frame backing
  * the input argument. Should be one or greater.
  *
diff --git a/tools/libxc/xc_memshr.c b/tools/libxc/xc_memshr.c
index 97e2e6a8d9..d0e4ee225b 100644
--- a/tools/libxc/xc_memshr.c
+++ b/tools/libxc/xc_memshr.c
@@ -239,6 +239,28 @@ int xc_memshr_debug_gref(xc_interface *xch,
     return xc_memshr_memop(xch, domid, &mso);
 }
 
+int xc_memshr_fork(xc_interface *xch, uint32_t pdomid, uint32_t domid)
+{
+    xen_mem_sharing_op_t mso;
+
+    memset(&mso, 0, sizeof(mso));
+
+    mso.op = XENMEM_sharing_op_fork;
+    mso.u.fork.parent_domain = pdomid;
+
+    return xc_memshr_memop(xch, domid, &mso);
+}
+
+int xc_memshr_fork_reset(xc_interface *xch, uint32_t domid)
+{
+    xen_mem_sharing_op_t mso;
+
+    memset(&mso, 0, sizeof(mso));
+    mso.op = XENMEM_sharing_op_fork_reset;
+
+    return xc_memshr_memop(xch, domid, &mso);
+}
+
 int xc_memshr_audit(xc_interface *xch)
 {
     xen_mem_sharing_op_t mso;
diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
index 54abb9db1f..75cb070587 100644
--- a/tools/libxl/libxl.h
+++ b/tools/libxl/libxl.h
@@ -1536,6 +1536,13 @@ int libxl_domain_create_new(libxl_ctx *ctx, libxl_domain_config *d_config,
                             const libxl_asyncop_how *ao_how,
                             const libxl_asyncprogress_how *aop_console_how)
                             LIBXL_EXTERNAL_CALLERS_ONLY;
+int libxl_domain_fork_vm(libxl_ctx *ctx, uint32_t pdomid, uint32_t *domid)
+                             LIBXL_EXTERNAL_CALLERS_ONLY;
+int libxl_domain_fork_launch_dm(libxl_ctx *ctx, libxl_domain_config *d_config,
+                                uint32_t domid,
+                                const libxl_asyncprogress_how *aop_console_how)
+                                LIBXL_EXTERNAL_CALLERS_ONLY;
+int libxl_domain_fork_reset(libxl_ctx *ctx, uint32_t domid);
 int libxl_domain_create_restore(libxl_ctx *ctx, libxl_domain_config *d_config,
                                 uint32_t *domid, int restore_fd,
                                 int send_back_fd,
diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
index 32d45dcef0..e0d219596c 100644
--- a/tools/libxl/libxl_create.c
+++ b/tools/libxl/libxl_create.c
@@ -536,12 +536,12 @@ out:
     return ret;
 }
 
-int libxl__domain_make(libxl__gc *gc, libxl_domain_config *d_config,
-                       libxl__domain_build_state *state,
-                       uint32_t *domid)
+static int libxl__domain_make_xs_entries(libxl__gc *gc, libxl_domain_config *d_config,
+                                         libxl__domain_build_state *state,
+                                         uint32_t domid)
 {
     libxl_ctx *ctx = libxl__gc_owner(gc);
-    int ret, rc, nb_vm;
+    int rc, nb_vm;
     const char *dom_type;
     char *uuid_string;
     char *dom_path, *vm_path, *libxl_path;
@@ -553,7 +553,6 @@ int libxl__domain_make(libxl__gc *gc, libxl_domain_config *d_config,
 
     /* convenience aliases */
     libxl_domain_create_info *info = &d_config->c_info;
-    libxl_domain_build_info *b_info = &d_config->b_info;
 
     uuid_string = libxl__uuid2string(gc, info->uuid);
     if (!uuid_string) {
@@ -561,64 +560,7 @@ int libxl__domain_make(libxl__gc *gc, libxl_domain_config *d_config,
         goto out;
     }
 
-    /* Valid domid here means we're soft resetting. */
-    if (!libxl_domid_valid_guest(*domid)) {
-        struct xen_domctl_createdomain create = {
-            .ssidref = info->ssidref,
-            .max_vcpus = b_info->max_vcpus,
-            .max_evtchn_port = b_info->event_channels,
-            .max_grant_frames = b_info->max_grant_frames,
-            .max_maptrack_frames = b_info->max_maptrack_frames,
-        };
-
-        if (info->type != LIBXL_DOMAIN_TYPE_PV) {
-            create.flags |= XEN_DOMCTL_CDF_hvm;
-            create.flags |=
-                libxl_defbool_val(info->hap) ? XEN_DOMCTL_CDF_hap : 0;
-            create.flags |=
-                libxl_defbool_val(info->oos) ? 0 : XEN_DOMCTL_CDF_oos_off;
-        }
-
-        assert(info->passthrough != LIBXL_PASSTHROUGH_DEFAULT);
-        LOG(DETAIL, "passthrough: %s",
-            libxl_passthrough_to_string(info->passthrough));
-
-        if (info->passthrough != LIBXL_PASSTHROUGH_DISABLED)
-            create.flags |= XEN_DOMCTL_CDF_iommu;
-
-        if (info->passthrough == LIBXL_PASSTHROUGH_SYNC_PT)
-            create.iommu_opts |= XEN_DOMCTL_IOMMU_no_sharept;
-
-        /* Ultimately, handle is an array of 16 uint8_t, same as uuid */
-        libxl_uuid_copy(ctx, (libxl_uuid *)&create.handle, &info->uuid);
-
-        ret = libxl__arch_domain_prepare_config(gc, d_config, &create);
-        if (ret < 0) {
-            LOGED(ERROR, *domid, "fail to get domain config");
-            rc = ERROR_FAIL;
-            goto out;
-        }
-
-        ret = xc_domain_create(ctx->xch, domid, &create);
-        if (ret < 0) {
-            LOGED(ERROR, *domid, "domain creation fail");
-            rc = ERROR_FAIL;
-            goto out;
-        }
-
-        rc = libxl__arch_domain_save_config(gc, d_config, state, &create);
-        if (rc < 0)
-            goto out;
-    }
-
-    ret = xc_cpupool_movedomain(ctx->xch, info->poolid, *domid);
-    if (ret < 0) {
-        LOGED(ERROR, *domid, "domain move fail");
-        rc = ERROR_FAIL;
-        goto out;
-    }
-
-    dom_path = libxl__xs_get_dompath(gc, *domid);
+    dom_path = libxl__xs_get_dompath(gc, domid);
     if (!dom_path) {
         rc = ERROR_FAIL;
         goto out;
@@ -626,12 +568,12 @@ int libxl__domain_make(libxl__gc *gc, libxl_domain_config *d_config,
 
     vm_path = GCSPRINTF("/vm/%s", uuid_string);
     if (!vm_path) {
-        LOGD(ERROR, *domid, "cannot allocate create paths");
+        LOGD(ERROR, domid, "cannot allocate create paths");
         rc = ERROR_FAIL;
         goto out;
     }
 
-    libxl_path = libxl__xs_libxl_path(gc, *domid);
+    libxl_path = libxl__xs_libxl_path(gc, domid);
     if (!libxl_path) {
         rc = ERROR_FAIL;
         goto out;
@@ -642,10 +584,10 @@ int libxl__domain_make(libxl__gc *gc, libxl_domain_config *d_config,
 
     roperm[0].id = 0;
     roperm[0].perms = XS_PERM_NONE;
-    roperm[1].id = *domid;
+    roperm[1].id = domid;
     roperm[1].perms = XS_PERM_READ;
 
-    rwperm[0].id = *domid;
+    rwperm[0].id = domid;
     rwperm[0].perms = XS_PERM_NONE;
 
 retry_transaction:
@@ -663,7 +605,7 @@ retry_transaction:
                     noperm, ARRAY_SIZE(noperm));
 
     xs_write(ctx->xsh, t, GCSPRINTF("%s/vm", dom_path), vm_path, strlen(vm_path));
-    rc = libxl__domain_rename(gc, *domid, 0, info->name, t);
+    rc = libxl__domain_rename(gc, domid, 0, info->name, t);
     if (rc)
         goto out;
 
@@ -740,7 +682,7 @@ retry_transaction:
 
     vm_list = libxl_list_vm(ctx, &nb_vm);
     if (!vm_list) {
-        LOGD(ERROR, *domid, "cannot get number of running guests");
+        LOGD(ERROR, domid, "cannot get number of running guests");
         rc = ERROR_FAIL;
         goto out;
     }
@@ -764,7 +706,7 @@ retry_transaction:
             t = 0;
             goto retry_transaction;
         }
-        LOGED(ERROR, *domid, "domain creation ""xenstore transaction commit failed");
+        LOGED(ERROR, domid, "domain creation ""xenstore transaction commit failed");
         rc = ERROR_FAIL;
         goto out;
     }
@@ -776,6 +718,80 @@ retry_transaction:
     return rc;
 }
 
+int libxl__domain_make(libxl__gc *gc, libxl_domain_config *d_config,
+                       libxl__domain_build_state *state,
+                       uint32_t *domid)
+{
+    libxl_ctx *ctx = libxl__gc_owner(gc);
+    int ret, rc;
+
+    /* convenience aliases */
+    libxl_domain_create_info *info = &d_config->c_info;
+    libxl_domain_build_info *b_info = &d_config->b_info;
+
+    /* Valid domid here means we're soft resetting. */
+    if (!libxl_domid_valid_guest(*domid)) {
+        struct xen_domctl_createdomain create = {
+            .ssidref = info->ssidref,
+            .max_vcpus = b_info->max_vcpus,
+            .max_evtchn_port = b_info->event_channels,
+            .max_grant_frames = b_info->max_grant_frames,
+            .max_maptrack_frames = b_info->max_maptrack_frames,
+        };
+
+        if (info->type != LIBXL_DOMAIN_TYPE_PV) {
+            create.flags |= XEN_DOMCTL_CDF_hvm;
+            create.flags |=
+                libxl_defbool_val(info->hap) ? XEN_DOMCTL_CDF_hap : 0;
+            create.flags |=
+                libxl_defbool_val(info->oos) ? 0 : XEN_DOMCTL_CDF_oos_off;
+        }
+
+        assert(info->passthrough != LIBXL_PASSTHROUGH_DEFAULT);
+        LOG(DETAIL, "passthrough: %s",
+            libxl_passthrough_to_string(info->passthrough));
+
+        if (info->passthrough != LIBXL_PASSTHROUGH_DISABLED)
+            create.flags |= XEN_DOMCTL_CDF_iommu;
+
+        if (info->passthrough == LIBXL_PASSTHROUGH_SYNC_PT)
+            create.iommu_opts |= XEN_DOMCTL_IOMMU_no_sharept;
+
+        /* Ultimately, handle is an array of 16 uint8_t, same as uuid */
+        libxl_uuid_copy(ctx, (libxl_uuid *)&create.handle, &info->uuid);
+
+        ret = libxl__arch_domain_prepare_config(gc, d_config, &create);
+        if (ret < 0) {
+            LOGED(ERROR, *domid, "fail to get domain config");
+            rc = ERROR_FAIL;
+            goto out;
+        }
+
+        ret = xc_domain_create(ctx->xch, domid, &create);
+        if (ret < 0) {
+            LOGED(ERROR, *domid, "domain creation fail");
+            rc = ERROR_FAIL;
+            goto out;
+        }
+
+        rc = libxl__arch_domain_save_config(gc, d_config, state, &create);
+        if (rc < 0)
+            goto out;
+    }
+
+    ret = xc_cpupool_movedomain(ctx->xch, info->poolid, *domid);
+    if (ret < 0) {
+        LOGED(ERROR, *domid, "domain move fail");
+        rc = ERROR_FAIL;
+        goto out;
+    }
+
+    rc = libxl__domain_make_xs_entries(gc, d_config, state, *domid);
+
+out:
+    return rc;
+}
+
 static int store_libxl_entry(libxl__gc *gc, uint32_t domid,
                              libxl_domain_build_info *b_info)
 {
@@ -1097,15 +1113,31 @@ static void initiate_domain_create(libxl__egc *egc,
     ret = libxl__domain_config_setdefault(gc,d_config,domid);
     if (ret) goto error_out;
 
-    ret = libxl__domain_make(gc, d_config, &dcs->build_state, &domid);
-    if (ret) {
-        LOGD(ERROR, domid, "cannot make domain: %d", ret);
+    if ( !d_config->dm_restore_file )
+    {
+        ret = libxl__domain_make(gc, d_config, &dcs->build_state, &domid);
         dcs->guest_domid = domid;
+
+        if (ret) {
+            LOGD(ERROR, domid, "cannot make domain: %d", ret);
+            ret = ERROR_FAIL;
+            goto error_out;
+        }
+    } else if ( dcs->guest_domid != INVALID_DOMID ) {
+        domid = dcs->guest_domid;
+
+        ret = libxl__domain_make_xs_entries(gc, d_config, &dcs->build_state, domid);
+        if (ret) {
+            LOGD(ERROR, domid, "cannot make domain: %d", ret);
+            ret = ERROR_FAIL;
+            goto error_out;
+        }
+    } else {
+        LOGD(ERROR, domid, "cannot make domain");
         ret = ERROR_FAIL;
         goto error_out;
     }
 
-    dcs->guest_domid = domid;
     dcs->sdss.dm.guest_domid = 0; /* means we haven't spawned */
 
     /* post-4.13 todo: move these next bits of defaulting to
@@ -1141,7 +1173,7 @@ static void initiate_domain_create(libxl__egc *egc,
     if (ret)
         goto error_out;
 
-    if (restore_fd >= 0 || dcs->domid_soft_reset != INVALID_DOMID) {
+    if (restore_fd >= 0 || dcs->domid_soft_reset != INVALID_DOMID || d_config->dm_restore_file) {
         LOGD(DEBUG, domid, "restoring, not running bootloader");
         domcreate_bootloader_done(egc, &dcs->bl, 0);
     } else  {
@@ -1217,7 +1249,16 @@ static void domcreate_bootloader_done(libxl__egc *egc,
     dcs->sdss.dm.callback = domcreate_devmodel_started;
     dcs->sdss.callback = domcreate_devmodel_started;
 
-    if (restore_fd < 0 && dcs->domid_soft_reset == INVALID_DOMID) {
+    if (restore_fd < 0 && dcs->domid_soft_reset == INVALID_DOMID && !d_config->dm_restore_file) {
+        rc = libxl__domain_build(gc, d_config, domid, state);
+        domcreate_rebuild_done(egc, dcs, rc);
+        return;
+    }
+
+    if ( d_config->dm_restore_file ) {
+        dcs->srs.dcs = dcs;
+        dcs->srs.ao = ao;
+        state->forked_vm = true;
         rc = libxl__domain_build(gc, d_config, domid, state);
         domcreate_rebuild_done(egc, dcs, rc);
         return;
@@ -1415,6 +1456,7 @@ static void domcreate_rebuild_done(libxl__egc *egc,
     /* convenience aliases */
     const uint32_t domid = dcs->guest_domid;
     libxl_domain_config *const d_config = dcs->guest_config;
+    libxl__domain_build_state *const state = &dcs->build_state;
 
     if (ret) {
         LOGD(ERROR, domid, "cannot (re-)build domain: %d", ret);
@@ -1422,6 +1464,9 @@ static void domcreate_rebuild_done(libxl__egc *egc,
         goto error_out;
     }
 
+    if ( d_config->dm_restore_file )
+        state->saved_state = GCSPRINTF("%s", d_config->dm_restore_file);
+
     store_libxl_entry(gc, domid, &d_config->b_info);
 
     libxl__multidev_begin(ao, &dcs->multidev);
@@ -1823,10 +1868,13 @@ static int do_domain_create(libxl_ctx *ctx, libxl_domain_config *d_config,
     GCNEW(cdcs);
     cdcs->dcs.ao = ao;
     cdcs->dcs.guest_config = d_config;
+    cdcs->dcs.guest_domid = *domid;
+
     libxl_domain_config_init(&cdcs->dcs.guest_config_saved);
     libxl_domain_config_copy(ctx, &cdcs->dcs.guest_config_saved, d_config);
     cdcs->dcs.restore_fd = cdcs->dcs.libxc_fd = restore_fd;
     cdcs->dcs.send_back_fd = send_back_fd;
+
     if (restore_fd > -1) {
         cdcs->dcs.restore_params = *params;
         rc = libxl__fd_flags_modify_save(gc, cdcs->dcs.restore_fd,
@@ -2069,6 +2117,43 @@ int libxl_domain_create_new(libxl_ctx *ctx, libxl_domain_config *d_config,
                             ao_how, aop_console_how);
 }
 
+int libxl_domain_fork_vm(libxl_ctx *ctx, uint32_t pdomid, uint32_t *domid)
+{
+    int rc;
+    struct xen_domctl_createdomain create = {0};
+    create.flags |= XEN_DOMCTL_CDF_hvm;
+    create.flags |= XEN_DOMCTL_CDF_hap;
+    create.flags |= XEN_DOMCTL_CDF_oos_off;
+    create.arch.emulation_flags = (XEN_X86_EMU_ALL & ~XEN_X86_EMU_VPCI);
+
+    create.ssidref = SECINITSID_DOMU;
+    create.max_vcpus = 1; // placeholder, will be cloned from pdomid
+    create.max_evtchn_port = 1023;
+    create.max_grant_frames = LIBXL_MAX_GRANT_FRAMES_DEFAULT;
+    create.max_maptrack_frames = LIBXL_MAX_MAPTRACK_FRAMES_DEFAULT;
+
+    if ( (rc = xc_domain_create(ctx->xch, domid, &create)) )
+        return rc;
+
+    if ( (rc = xc_memshr_fork(ctx->xch, pdomid, *domid)) )
+        xc_domain_destroy(ctx->xch, *domid);
+
+    return rc;
+}
+
+int libxl_domain_fork_launch_dm(libxl_ctx *ctx, libxl_domain_config *d_config,
+                                uint32_t domid,
+                                const libxl_asyncprogress_how *aop_console_how)
+{
+    unset_disk_colo_restore(d_config);
+    return do_domain_create(ctx, d_config, &domid, -1, -1, 0, 0, aop_console_how);
+}
+
+int libxl_domain_fork_reset(libxl_ctx *ctx, uint32_t domid)
+{
+    return xc_memshr_fork_reset(ctx->xch, domid);
+}
+
 int libxl_domain_create_restore(libxl_ctx *ctx, libxl_domain_config *d_config,
                                 uint32_t *domid, int restore_fd,
                                 int send_back_fd,
diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
index dac1b8ddb8..a119e789a7 100644
--- a/tools/libxl/libxl_dm.c
+++ b/tools/libxl/libxl_dm.c
@@ -2784,7 +2784,7 @@ static void device_model_spawn_outcome(libxl__egc *egc,
 
     libxl__domain_build_state *state = dmss->build_state;
 
-    if (state->saved_state) {
+    if (state->saved_state && !state->forked_vm) {
         ret2 = unlink(state->saved_state);
         if (ret2) {
             LOGED(ERROR, dmss->guest_domid, "%s: failed to remove device-model state %s",
diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
index cdb294ab8d..95e6ecc9d3 100644
--- a/tools/libxl/libxl_dom.c
+++ b/tools/libxl/libxl_dom.c
@@ -392,9 +392,12 @@ int libxl__build_pre(libxl__gc *gc, uint32_t domid,
     libxl_domain_build_info *const info = &d_config->b_info;
     libxl_ctx *ctx = libxl__gc_owner(gc);
     char *xs_domid, *con_domid;
-    int rc;
+    int rc = 0;
     uint64_t size;
 
+    if ( state->forked_vm )
+        goto skip_fork;
+
     if (xc_domain_max_vcpus(ctx->xch, domid, info->max_vcpus) != 0) {
         LOG(ERROR, "Couldn't set max vcpu count");
         return ERROR_FAIL;
@@ -499,29 +502,6 @@ int libxl__build_pre(libxl__gc *gc, uint32_t domid,
         }
     }
 
-
-    rc = libxl__arch_extra_memory(gc, info, &size);
-    if (rc < 0) {
-        LOGE(ERROR, "Couldn't get arch extra constant memory size");
-        return ERROR_FAIL;
-    }
-
-    if (xc_domain_setmaxmem(ctx->xch, domid, info->target_memkb + size) < 0) {
-        LOGE(ERROR, "Couldn't set max memory");
-        return ERROR_FAIL;
-    }
-
-    xs_domid = xs_read(ctx->xsh, XBT_NULL, "/tool/xenstored/domid", NULL);
-    state->store_domid = xs_domid ? atoi(xs_domid) : 0;
-    free(xs_domid);
-
-    con_domid = xs_read(ctx->xsh, XBT_NULL, "/tool/xenconsoled/domid", NULL);
-    state->console_domid = con_domid ? atoi(con_domid) : 0;
-    free(con_domid);
-
-    state->store_port = xc_evtchn_alloc_unbound(ctx->xch, domid, state->store_domid);
-    state->console_port = xc_evtchn_alloc_unbound(ctx->xch, domid, state->console_domid);
-
     if (info->type != LIBXL_DOMAIN_TYPE_PV)
         hvm_set_conf_params(ctx->xch, domid, info);
 
@@ -556,8 +536,34 @@ int libxl__build_pre(libxl__gc *gc, uint32_t domid,
                          info->altp2m);
     }
 
+    rc = libxl__arch_extra_memory(gc, info, &size);
+    if (rc < 0) {
+        LOGE(ERROR, "Couldn't get arch extra constant memory size");
+        return ERROR_FAIL;
+    }
+
+    if (xc_domain_setmaxmem(ctx->xch, domid, info->target_memkb + size) < 0) {
+        LOGE(ERROR, "Couldn't set max memory");
+        return ERROR_FAIL;
+    }
+
     rc = libxl__arch_domain_create(gc, d_config, domid);
+    if ( rc )
+        goto out;
 
+skip_fork:
+    xs_domid = xs_read(ctx->xsh, XBT_NULL, "/tool/xenstored/domid", NULL);
+    state->store_domid = xs_domid ? atoi(xs_domid) : 0;
+    free(xs_domid);
+
+    con_domid = xs_read(ctx->xsh, XBT_NULL, "/tool/xenconsoled/domid", NULL);
+    state->console_domid = con_domid ? atoi(con_domid) : 0;
+    free(con_domid);
+
+    state->store_port = xc_evtchn_alloc_unbound(ctx->xch, domid, state->store_domid);
+    state->console_port = xc_evtchn_alloc_unbound(ctx->xch, domid, state->console_domid);
+
+out:
     return rc;
 }
 
@@ -615,6 +621,9 @@ int libxl__build_post(libxl__gc *gc, uint32_t domid,
     char **ents;
     int i, rc;
 
+    if ( state->forked_vm )
+        goto skip_fork;
+
     if (info->num_vnuma_nodes && !info->num_vcpu_soft_affinity) {
         rc = set_vnuma_affinity(gc, domid, info);
         if (rc)
@@ -639,6 +648,7 @@ int libxl__build_post(libxl__gc *gc, uint32_t domid,
         }
     }
 
+skip_fork:
     ents = libxl__calloc(gc, 12 + (info->max_vcpus * 2) + 2, sizeof(char *));
     ents[0] = "memory/static-max";
     ents[1] = GCSPRINTF("%"PRId64, info->max_memkb);
@@ -901,14 +911,16 @@ static int hvm_build_set_params(xc_interface *handle, uint32_t domid,
                                 libxl_domain_build_info *info,
                                 int store_evtchn, unsigned long *store_mfn,
                                 int console_evtchn, unsigned long *console_mfn,
-                                domid_t store_domid, domid_t console_domid)
+                                domid_t store_domid, domid_t console_domid,
+                                bool forked_vm)
 {
     struct hvm_info_table *va_hvm;
     uint8_t *va_map, sum;
     uint64_t str_mfn, cons_mfn;
     int i;
 
-    if (info->type == LIBXL_DOMAIN_TYPE_HVM) {
+    if ( info->type == LIBXL_DOMAIN_TYPE_HVM && !forked_vm )
+    {
         va_map = xc_map_foreign_range(handle, domid,
                                       XC_PAGE_SIZE, PROT_READ | PROT_WRITE,
                                       HVM_INFO_PFN);
@@ -1224,6 +1236,23 @@ int libxl__build_hvm(libxl__gc *gc, uint32_t domid,
     struct xc_dom_image *dom = NULL;
     bool device_model = info->type == LIBXL_DOMAIN_TYPE_HVM ? true : false;
 
+    if ( state->forked_vm )
+    {
+        rc = hvm_build_set_params(ctx->xch, domid, info, state->store_port,
+                                  &state->store_mfn, state->console_port,
+                                  &state->console_mfn, state->store_domid,
+                                  state->console_domid, state->forked_vm);
+
+        if ( rc )
+            return rc;
+
+        return xc_dom_gnttab_seed(ctx->xch, domid, true,
+                                  state->console_mfn,
+                                  state->store_mfn,
+                                  state->console_domid,
+                                  state->store_domid);
+    }
+
     xc_dom_loginit(ctx->xch);
 
     /*
@@ -1348,7 +1377,7 @@ int libxl__build_hvm(libxl__gc *gc, uint32_t domid,
     rc = hvm_build_set_params(ctx->xch, domid, info, state->store_port,
                                &state->store_mfn, state->console_port,
                                &state->console_mfn, state->store_domid,
-                               state->console_domid);
+                               state->console_domid, false);
     if (rc != 0) {
         LOG(ERROR, "hvm build set params failed");
         goto out;
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index b5adbfe4b7..ea6fe133a5 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -1360,6 +1360,7 @@ typedef struct {
 
     char *saved_state;
     int dm_monitor_fd;
+    bool forked_vm;
 
     libxl__file_reference pv_kernel;
     libxl__file_reference pv_ramdisk;
diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
index 7921950f6a..7c4c4057a9 100644
--- a/tools/libxl/libxl_types.idl
+++ b/tools/libxl/libxl_types.idl
@@ -956,6 +956,7 @@ libxl_domain_config = Struct("domain_config", [
     ("on_watchdog", libxl_action_on_shutdown),
     ("on_crash", libxl_action_on_shutdown),
     ("on_soft_reset", libxl_action_on_shutdown),
+    ("dm_restore_file", string, {'const': True}),
     ], dir=DIR_IN)
 
 libxl_diskinfo = Struct("diskinfo", [
diff --git a/tools/xl/xl.h b/tools/xl/xl.h
index 60bdad8ffb..9bdad6526e 100644
--- a/tools/xl/xl.h
+++ b/tools/xl/xl.h
@@ -31,6 +31,7 @@ struct cmd_spec {
 };
 
 struct domain_create {
+    uint32_t ddomid; /* fork launch dm for this domid */
     int debug;
     int daemonize;
     int monitor; /* handle guest reboots etc */
@@ -45,6 +46,7 @@ struct domain_create {
     const char *config_file;
     char *extra_config; /* extra config string */
     const char *restore_file;
+    const char *dm_restore_file;
     char *colo_proxy_script;
     bool userspace_colo_proxy;
     int migrate_fd; /* -1 means none */
@@ -127,6 +129,9 @@ int main_pciassignable_remove(int argc, char **argv);
 int main_pciassignable_list(int argc, char **argv);
 #ifndef LIBXL_HAVE_NO_SUSPEND_RESUME
 int main_restore(int argc, char **argv);
+int main_fork_vm(int argc, char **argv);
+int main_fork_launch_dm(int argc, char **argv);
+int main_fork_reset(int argc, char **argv);
 int main_migrate_receive(int argc, char **argv);
 int main_save(int argc, char **argv);
 int main_migrate(int argc, char **argv);
diff --git a/tools/xl/xl_cmdtable.c b/tools/xl/xl_cmdtable.c
index 5baa6023aa..94217e4ed4 100644
--- a/tools/xl/xl_cmdtable.c
+++ b/tools/xl/xl_cmdtable.c
@@ -180,6 +180,28 @@ struct cmd_spec cmd_table[] = {
       "-V, --vncviewer          Connect to the VNC display after the domain is created.\n"
       "-A, --vncviewer-autopass Pass VNC password to viewer via stdin."
     },
+    { "fork-vm",
+      &main_fork_vm, 0, 1,
+      "Fork a domain from the running parent domid",
+      "[options] <ParentDomid>",
+      "-h                       Print this help.\n"
+      "-d                       Enable debug messages.\n"
+    },
+    { "fork-launch-dm",
+      &main_fork_launch_dm, 0, 1,
+      "Launch the device model for a forked VM",
+      "[options] <ConfigFile> <DmRestoreFile> <Domid>",
+      "-h                       Print this help.\n"
+      "-p                       Do not unpause domain after restoring it.\n"
+      "-d                       Enable debug messages.\n"
+    },
+    { "fork-reset",
+      &main_fork_reset, 0, 1,
+      "Launch the device model for a forked VM",
+      "[options] <Domid>",
+      "-h                       Print this help.\n"
+      "-d                       Enable debug messages.\n"
+    },
     { "migrate-receive",
       &main_migrate_receive, 0, 1,
       "Restore a domain from a saved state",
diff --git a/tools/xl/xl_saverestore.c b/tools/xl/xl_saverestore.c
index 9be033fe65..c1dd74f33e 100644
--- a/tools/xl/xl_saverestore.c
+++ b/tools/xl/xl_saverestore.c
@@ -229,6 +229,102 @@ int main_restore(int argc, char **argv)
     return EXIT_SUCCESS;
 }
 
+int main_fork_vm(int argc, char **argv)
+{
+    int debug = 0;
+    uint32_t pdomid = 0, domid = INVALID_DOMID;
+    int opt;
+
+    SWITCH_FOREACH_OPT(opt, "d", NULL, "fork-vm", 1) {
+    case 'd':
+        debug = 1;
+        break;
+    }
+
+    if (argc-optind == 1) {
+        pdomid = atoi(argv[optind]);
+    } else {
+        help("fork-vm");
+        return EXIT_FAILURE;
+    }
+
+    if (libxl_domain_fork_vm(ctx, pdomid, &domid) || domid == INVALID_DOMID)
+        return EXIT_FAILURE;
+
+    fprintf(stderr, "VM fork created with domid: %u\n", domid);
+    return EXIT_SUCCESS;
+}
+
+int main_fork_launch_dm(int argc, char **argv)
+{
+    const char *config_file = NULL;
+    const char *dm_restore_file = NULL;
+    struct domain_create dom_info;
+    int paused = 0, debug = 0;
+    uint32_t ddomid = 0;
+    int opt, rc;
+
+    SWITCH_FOREACH_OPT(opt, "pd", NULL, "fork-launch-dm", 1) {
+    case 'p':
+        paused = 1;
+        break;
+    case 'd':
+        debug = 1;
+        break;
+    }
+
+    if (argc-optind == 3) {
+        config_file = argv[optind];
+        dm_restore_file = argv[optind + 1];
+        ddomid = atoi(argv[optind + 2]);
+    } else {
+        help("fork-launch-dm");
+        return EXIT_FAILURE;
+    }
+
+    memset(&dom_info, 0, sizeof(dom_info));
+    dom_info.ddomid = ddomid;
+    dom_info.dm_restore_file = dm_restore_file;
+    dom_info.debug = debug;
+    dom_info.paused = paused;
+    dom_info.config_file = config_file;
+    dom_info.migrate_fd = -1;
+    dom_info.send_back_fd = -1;
+
+    rc = create_domain(&dom_info);
+    if (rc < 0)
+        return EXIT_FAILURE;
+
+    return EXIT_SUCCESS;
+}
+
+int main_fork_reset(int argc, char **argv)
+{
+    int debug = 0;
+    uint32_t domid = 0;
+    int opt, rc;
+
+    SWITCH_FOREACH_OPT(opt, "d", NULL, "fork-reset", 1)
+    {
+    case 'd':
+        debug = 1;
+        break;
+    }
+
+    if (argc-optind == 1) {
+        domid = atoi(argv[optind]);
+    } else {
+        help("fork-reset");
+        return EXIT_FAILURE;
+    }
+
+    rc = libxl_domain_fork_reset(ctx, domid);
+    if (rc < 0)
+        return EXIT_FAILURE;
+
+    return EXIT_SUCCESS;
+}
+
 int main_save(int argc, char **argv)
 {
     uint32_t domid;
diff --git a/tools/xl/xl_vmcontrol.c b/tools/xl/xl_vmcontrol.c
index e520b1da79..d9cb19c599 100644
--- a/tools/xl/xl_vmcontrol.c
+++ b/tools/xl/xl_vmcontrol.c
@@ -645,6 +645,7 @@ int create_domain(struct domain_create *dom_info)
 
     libxl_domain_config d_config;
 
+    uint32_t ddomid = dom_info->ddomid; // launch dm for this domain iff set
     int debug = dom_info->debug;
     int daemonize = dom_info->daemonize;
     int monitor = dom_info->monitor;
@@ -655,6 +656,7 @@ int create_domain(struct domain_create *dom_info)
     const char *restore_file = dom_info->restore_file;
     const char *config_source = NULL;
     const char *restore_source = NULL;
+    const char *dm_restore_file = dom_info->dm_restore_file;
     int migrate_fd = dom_info->migrate_fd;
     bool config_in_json;
 
@@ -923,6 +925,12 @@ start:
          * restore/migrate-receive it again.
          */
         restoring = 0;
+    } else if ( ddomid ) {
+        d_config.dm_restore_file = dm_restore_file;
+        ret = libxl_domain_fork_launch_dm(ctx, &d_config, ddomid,
+                                          autoconnect_console_how);
+        domid = ddomid;
+        ddomid = INVALID_DOMID;
     } else if (domid_soft_reset != INVALID_DOMID) {
         /* Do soft reset. */
         ret = libxl_domain_soft_reset(ctx, &d_config, domid_soft_reset,
-- 
2.20.1


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Re: [Xen-devel] [PATCH v3 00/18] VM forking

[George Dunlap]

On 12/30/19 4:11 PM, Tamas K Lengyel wrote:
> The following series implements VM forking for Intel HVM guests to allow for
> the fast creation of identical VMs without the assosciated high startup costs
> of booting or restoring the VM from a savefile.

Tamas,

This doesn't seem to apply to staging.  Could you give me a commit hash
to which it should apply?

Thanks,
 -George

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Re: [Xen-devel] [PATCH v3 00/18] VM forking

[Tamas K Lengyel]

On Wed, Jan 8, 2020 at 7:58 AM George Dunlap <george.dunlap@citrix.com> wrote:
>
> On 12/30/19 4:11 PM, Tamas K Lengyel wrote:
> > The following series implements VM forking for Intel HVM guests to allow for
> > the fast creation of identical VMs without the assosciated high startup costs
> > of booting or restoring the VM from a savefile.
>
> Tamas,
>
> This doesn't seem to apply to staging.  Could you give me a commit hash
> to which it should apply?

Hi George,
huh it's weird. I rebased it before I sent on staging but somehow the
latest commit in staging it seems was a commit from April 2019, which
doesn't seem right. If this was just on one system I would say I just
had a stale branch on that system and forgot to pull it before the
rebase but it's actually happened on both my test systems
independently. Also, with my v2 branch of this series was branched
from a more recent version of staging. I really don't know what
happened... I'll be sending v4 shortly.

Tamas

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