x86/mem_sharing: make fork_reset more configurable

Allow specify distinct parts of the fork VM to be reset. This is useful when a
fuzzing operation involves mapping in only a handful of pages that are known
ahead of time. Throwing these pages away just to be re-copied immediately is
expensive, thus allowing to specify partial resets can speed things up.

Also allow resetting to be initiated from vm_event responses as an
optiomization.

Signed-off-by: Tamas K Lengyel <tamas.lengyel@intel.com>

diff --git a/tools/include/xenctrl.h b/tools/include/xenctrl.h
index 1df41d6033f20375445a1c755244b271e1538979..159eaac050f23a8868f4005e110540e9e58871f7 100644 (file)
--- a/tools/include/xenctrl.h
+++ b/tools/include/xenctrl.h
@@ -2292,7 +2292,8 @@ int xc_memshr_fork(xc_interface *xch,
  *
  * 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);
+int xc_memshr_fork_reset(xc_interface *xch, uint32_t forked_domain,
+                         bool reset_state, bool reset_memory);
 
 /* Debug calls: return the number of pages referencing the shared frame backing
  * the input argument. Should be one or greater.

diff --git a/tools/libs/ctrl/xc_memshr.c b/tools/libs/ctrl/xc_memshr.c
index a6cfd7dccf0a0b0281db73f25aaca1ffdf95450b..a0d0b894e2172c1433df4606a50c5f4cdc1e2373 100644 (file)
--- a/tools/libs/ctrl/xc_memshr.c
+++ b/tools/libs/ctrl/xc_memshr.c
@@ -257,12 +257,17 @@ int xc_memshr_fork(xc_interface *xch, uint32_t pdomid, uint32_t domid,
     return xc_memshr_memop(xch, domid, &mso);
 }
 
-int xc_memshr_fork_reset(xc_interface *xch, uint32_t domid)
+int xc_memshr_fork_reset(xc_interface *xch, uint32_t domid, bool reset_state,
+                         bool reset_memory)
 {
     xen_mem_sharing_op_t mso;
 
     memset(&mso, 0, sizeof(mso));
     mso.op = XENMEM_sharing_op_fork_reset;
+    if ( reset_state )
+        mso.u.fork.flags |= XENMEM_FORK_RESET_STATE;
+    if ( reset_memory )
+        mso.u.fork.flags |= XENMEM_FORK_RESET_MEMORY;
 
     return xc_memshr_memop(xch, domid, &mso);
 }

diff --git a/xen/arch/x86/include/asm/mem_sharing.h b/xen/arch/x86/include/asm/mem_sharing.h
index b4a8e8795a5dfe4a7eb5e045a0ac1c24df60e621..fca5ec8aeb25be222d84df9acf6c06bc3300f43e 100644 (file)
--- a/xen/arch/x86/include/asm/mem_sharing.h
+++ b/xen/arch/x86/include/asm/mem_sharing.h
@@ -85,6 +85,9 @@ static inline bool mem_sharing_is_fork(const struct domain *d)
 int mem_sharing_fork_page(struct domain *d, gfn_t gfn,
                           bool unsharing);
 
+int mem_sharing_fork_reset(struct domain *d, bool reset_state,
+                           bool reset_memory);
+
 /*
  * If called by a foreign domain, possible errors are
  *   -EBUSY -> ring full
@@ -148,6 +151,12 @@ static inline int mem_sharing_fork_page(struct domain *d, gfn_t gfn, bool lock)
     return -EOPNOTSUPP;
 }
 
+static inline int mem_sharing_fork_reset(struct domain *d, bool reset_state,
+                                         bool reset_memory)
+{
+    return -EOPNOTSUPP;
+}
+
 #endif
 
 #endif /* __MEM_SHARING_H__ */

diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c
index 8ffe2e3f212af3f1d3c5421749f64e8ecb3d91cf..818a3fd331f6d16e8656d1c49ca4b0f7696b142f 100644 (file)
--- a/xen/arch/x86/mm/mem_sharing.c
+++ b/xen/arch/x86/mm/mem_sharing.c
@@ -1901,15 +1901,19 @@ static int fork(struct domain *cd, struct domain *d, uint16_t flags)
  * footprints the hypercall continuation should be implemented (or if this
  * feature needs to be become "stable").
  */
-static int mem_sharing_fork_reset(struct domain *d)
+int mem_sharing_fork_reset(struct domain *d, bool reset_state,
+                           bool reset_memory)
 {
-    int rc;
+    int rc = 0;
     struct domain *pd = d->parent;
     struct p2m_domain *p2m = p2m_get_hostp2m(d);
     struct page_info *page, *tmp;
 
     domain_pause(d);
 
+    if ( !reset_memory )
+        goto state;
+
     /* need recursive lock because we will free pages */
     spin_lock_recursive(&d->page_alloc_lock);
     page_list_for_each_safe(page, tmp, &d->page_list)
@@ -1942,7 +1946,9 @@ static int mem_sharing_fork_reset(struct domain *d)
     }
     spin_unlock_recursive(&d->page_alloc_lock);
 
-    rc = copy_settings(d, pd, d->arch.hvm.mem_sharing.empty_p2m);
+ state:
+    if ( reset_state )
+        rc = copy_settings(d, pd, d->arch.hvm.mem_sharing.empty_p2m);
 
     domain_unpause(d);
 
@@ -2248,15 +2254,21 @@ int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg)
 
     case XENMEM_sharing_op_fork_reset:
     {
+        bool reset_state = mso.u.fork.flags & XENMEM_FORK_RESET_STATE;
+        bool reset_memory = mso.u.fork.flags & XENMEM_FORK_RESET_MEMORY;
+
         rc = -EINVAL;
-        if ( mso.u.fork.pad || mso.u.fork.flags )
+        if ( mso.u.fork.pad || (!reset_state && !reset_memory) )
+            goto out;
+        if ( mso.u.fork.flags &
+             ~(XENMEM_FORK_RESET_STATE | XENMEM_FORK_RESET_MEMORY) )
             goto out;
 
         rc = -ENOSYS;
         if ( !d->parent )
             goto out;
 
-        rc = mem_sharing_fork_reset(d);
+        rc = mem_sharing_fork_reset(d, reset_state, reset_memory);
         break;
     }
 

diff --git a/xen/common/vm_event.c b/xen/common/vm_event.c
index 84cf52636bc4b7c7602fb4a27658f95ffe76a17c..a7b192be0d4eb6d3bc494ac526d564e22f13bbb0 100644 (file)
--- a/xen/common/vm_event.c
+++ b/xen/common/vm_event.c
@@ -28,6 +28,11 @@
 #include <asm/p2m.h>
 #include <asm/monitor.h>
 #include <asm/vm_event.h>
+
+#ifdef CONFIG_MEM_SHARING
+#include <asm/mem_sharing.h>
+#endif
+
 #include <xsm/xsm.h>
 #include <public/hvm/params.h>
 
@@ -394,6 +399,15 @@ static int vm_event_resume(struct domain *d, struct vm_event_domain *ved)
             if ( rsp.reason == VM_EVENT_REASON_MEM_PAGING )
                 p2m_mem_paging_resume(d, &rsp);
 #endif
+#ifdef CONFIG_MEM_SHARING
+            do {
+                bool reset_state = rsp.flags & VM_EVENT_FLAG_RESET_FORK_STATE;
+                bool reset_mem = rsp.flags & VM_EVENT_FLAG_RESET_FORK_MEMORY;
+
+                if ( reset_state || reset_mem )
+                    mem_sharing_fork_reset(d, reset_state, reset_mem);
+            } while(0);
+#endif
 
             /*
              * Check emulation flags in the arch-specific handler only, as it

diff --git a/xen/include/public/memory.h b/xen/include/public/memory.h
index d44c256b3c1e516d9522d67d29c0f42bbd64ac72..2a4edfc84ba1779cdfda6e683a055a54f009cc02 100644 (file)
--- a/xen/include/public/memory.h
+++ b/xen/include/public/memory.h
@@ -541,12 +541,14 @@ struct xen_mem_sharing_op {
                 uint32_t gref;     /* IN: gref to debug         */
             } u;
         } debug;
-        struct mem_sharing_op_fork {      /* OP_FORK */
+        struct mem_sharing_op_fork {      /* OP_FORK/_RESET */
             domid_t parent_domain;        /* IN: parent's domain id */
 /* These flags only makes sense for short-lived forks */
 #define XENMEM_FORK_WITH_IOMMU_ALLOWED (1u << 0)
 #define XENMEM_FORK_BLOCK_INTERRUPTS   (1u << 1)
 #define XENMEM_FORK_EMPTY_P2M          (1u << 2)
+#define XENMEM_FORK_RESET_STATE        (1u << 3)
+#define XENMEM_FORK_RESET_MEMORY       (1u << 4)
             uint16_t flags;               /* IN: optional settings */
             uint32_t pad;                 /* Must be set to 0 */
         } fork;

diff --git a/xen/include/public/vm_event.h b/xen/include/public/vm_event.h
index d443a2486296bca4d45fa674682e3231df3bfa26..07f106f81184be123a83952a54ff5b4977a7ceef 100644 (file)
--- a/xen/include/public/vm_event.h
+++ b/xen/include/public/vm_event.h
@@ -127,6 +127,14 @@
  * Reset the vmtrace buffer (if vmtrace is enabled)
  */
 #define VM_EVENT_FLAG_RESET_VMTRACE      (1 << 13)
+/*
+ * Reset the VM state (if VM is fork)
+ */
+#define VM_EVENT_FLAG_RESET_FORK_STATE   (1 << 14)
+/*
+ * Remove unshared entried from physmap (if VM is fork)
+ */
+#define VM_EVENT_FLAG_RESET_FORK_MEMORY  (1 << 15)
 
 /*
  * Reasons for the vm event request