[Xen-devel] [PATCH RFC 6/9] xen, libxc: Request page fault injection via libxc

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

Added new XEN_DOMCTL_set_pagefault_info hypercall, used by libxc's
new xc_domain_set_pagefault_info() function to set per-domain page
fault injection information. This information is then used to call
hvm_inject_page_fault() at the first VMENTRY where the guest status
matches and there are no other pending traps.

Signed-off-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
---
 tools/libxc/xc_domain.c     |   17 +++++++++++++++++
 tools/libxc/xenctrl.h       |    4 ++++
 xen/arch/x86/hvm/vmx/vmx.c  |   39 +++++++++++++++++++++++++++++++++++++++
 xen/common/domain.c         |    5 +++++
 xen/common/domctl.c         |   21 +++++++++++++++++++++
 xen/include/public/domctl.h |   14 ++++++++++++++
 xen/include/xen/sched.h     |    7 +++++++
 7 files changed, 107 insertions(+)

diff --git a/tools/libxc/xc_domain.c b/tools/libxc/xc_domain.c
index d5d6d12..701b65f 100644
--- a/tools/libxc/xc_domain.c
+++ b/tools/libxc/xc_domain.c
@@ -486,6 +486,23 @@ int xc_domain_hvm_setcontext(xc_interface *xch,
     return ret;
 }
 
+int xc_domain_set_pagefault_info(xc_interface *xch,
+                                 uint32_t domid,
+                                 xen_domctl_set_pagefault_info_t *info)
+{
+    DECLARE_DOMCTL;
+
+    if (info == NULL)
+        return -1;
+
+    domctl.cmd = XEN_DOMCTL_set_pagefault_info;
+    domctl.domain = (domid_t)domid;
+    domctl.u.set_pagefault_info.address_space = info->address_space;
+    domctl.u.set_pagefault_info.virtual_address = info->virtual_address;
+    domctl.u.set_pagefault_info.write_access = info->write_access;
+    return do_domctl(xch, &domctl);
+}
+
 int xc_vcpu_getcontext(xc_interface *xch,
                        uint32_t domid,
                        uint32_t vcpu,
diff --git a/tools/libxc/xenctrl.h b/tools/libxc/xenctrl.h
index abd8947..088f02f 100644
--- a/tools/libxc/xenctrl.h
+++ b/tools/libxc/xenctrl.h
@@ -752,6 +752,10 @@ int xc_domain_hvm_setcontext(xc_interface *xch,
 const char *xc_domain_get_native_protocol(xc_interface *xch,
                                           uint32_t domid);
 
+int xc_domain_set_pagefault_info(xc_interface *xch,
+                                 uint32_t domid,
+                                 xen_domctl_set_pagefault_info_t *info);
+
 /**
  * This function returns information about the execution context of a
  * particular vcpu of a domain.
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index b4c12cd..4a9a7c8 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -416,6 +416,7 @@ static void vmx_restore_dr(struct vcpu *v)
 static void vmx_vmcs_save(struct vcpu *v, struct hvm_hw_cpu *c)
 {
     unsigned long ev;
+    unsigned long cs_arbytes;
 
     vmx_vmcs_enter(v);
 
@@ -430,6 +431,9 @@ static void vmx_vmcs_save(struct vcpu *v, struct hvm_hw_cpu 
*c)
     __vmread(GUEST_SYSENTER_CS, &c->sysenter_cs);
     __vmread(GUEST_SYSENTER_ESP, &c->sysenter_esp);
     __vmread(GUEST_SYSENTER_EIP, &c->sysenter_eip);
+    __vmread(GUEST_CS_AR_BYTES, &cs_arbytes);
+
+    c->cs_arbytes = (uint32_t)cs_arbytes;
 
     c->pending_event = 0;
     c->error_code = 0;
@@ -3111,6 +3115,39 @@ out:
         nvmx_idtv_handling();
 }
 
+static void check_pf_injection(void)
+{
+    struct vcpu *curr = current;
+    struct domain *d = curr->domain;
+    struct hvm_hw_cpu ctxt;
+    uint32_t cs_dpl;
+
+    if ( !is_hvm_domain(d) || d->fault_info.virtual_address == 0 )
+        return;
+
+    memset(&ctxt, 0, sizeof(struct hvm_hw_cpu));
+    hvm_funcs.save_cpu_ctxt(curr, &ctxt);
+
+    cs_dpl = (ctxt.cs_arbytes >> 5) & 3;
+
+    if ( cs_dpl == 3 /* Guest is in user mode */
+         && !ctxt.pending_event
+         && ctxt.cr3 == d->fault_info.address_space )
+    {
+        /* Cache */
+        uint64_t virtual_address = d->fault_info.virtual_address;
+        uint32_t write_access = d->fault_info.write_access;
+
+        /* Reset */
+        d->fault_info.address_space = 0;
+        d->fault_info.virtual_address = 0;
+        d->fault_info.write_access = 0;
+
+        hvm_inject_page_fault((write_access << 1) | PFEC_user_mode,
+            virtual_address);
+    }
+}
+
 void vmx_vmenter_helper(const struct cpu_user_regs *regs)
 {
     struct vcpu *curr = current;
@@ -3151,6 +3188,8 @@ void vmx_vmenter_helper(const struct cpu_user_regs *regs)
     if ( unlikely(need_flush) )
         vpid_sync_all();
 
+    check_pf_injection();
+
  out:
     HVMTRACE_ND(VMENTRY, 0, 1/*cycles*/, 0, 0, 0, 0, 0, 0, 0);
 
diff --git a/xen/common/domain.c b/xen/common/domain.c
index c3a576e..9402924 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -255,6 +255,11 @@ struct domain *domain_create(
 
     d->domain_id = domid;
 
+    /* Memory introspection page fault variables set-up. */
+    d->fault_info.address_space = 0;
+    d->fault_info.virtual_address = 0;
+    d->fault_info.write_access = 0;
+
     lock_profile_register_struct(LOCKPROF_TYPE_PERDOM, d, domid, "Domain");
 
     if ( (err = xsm_alloc_security_domain(d)) != 0 )
diff --git a/xen/common/domctl.c b/xen/common/domctl.c
index 000993f..461e207 100644
--- a/xen/common/domctl.c
+++ b/xen/common/domctl.c
@@ -975,6 +975,27 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) 
u_domctl)
     }
     break;
 
+    case XEN_DOMCTL_set_pagefault_info:
+    {
+        struct domain *d;
+
+        ret = -ESRCH;
+        d = rcu_lock_domain_by_id(op->domain);
+        if ( d != NULL )
+        {
+            d->fault_info.address_space =
+                op->u.set_pagefault_info.address_space;
+            d->fault_info.virtual_address =
+                op->u.set_pagefault_info.virtual_address;
+            d->fault_info.write_access =
+                op->u.set_pagefault_info.write_access;
+
+            rcu_unlock_domain(d);
+            ret = 0;
+        }
+    }
+    break;
+
     default:
         ret = arch_do_domctl(op, d, u_domctl);
         break;
diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
index 5b11bbf..c8bf3f8 100644
--- a/xen/include/public/domctl.h
+++ b/xen/include/public/domctl.h
@@ -936,6 +936,18 @@ typedef struct xen_domctl_vcpu_msrs xen_domctl_vcpu_msrs_t;
 DEFINE_XEN_GUEST_HANDLE(xen_domctl_vcpu_msrs_t);
 #endif
 
+/* XEN_DOMCTL_set_pagefault_info requests that a page fault occur at
+ * the next VMENTRY.
+ *  */
+struct xen_domctl_set_pagefault_info {
+    uint64_t address_space;
+    uint64_t virtual_address;
+    uint32_t write_access;
+};
+typedef struct xen_domctl_set_pagefault_info xen_domctl_set_pagefault_info_t;
+DEFINE_XEN_GUEST_HANDLE(xen_domctl_set_pagefault_info_t);
+
+
 struct xen_domctl {
     uint32_t cmd;
 #define XEN_DOMCTL_createdomain                   1
@@ -1012,6 +1024,7 @@ struct xen_domctl {
 #define XEN_DOMCTL_gdbsx_pausevcpu             1001
 #define XEN_DOMCTL_gdbsx_unpausevcpu           1002
 #define XEN_DOMCTL_gdbsx_domstatus             1003
+#define XEN_DOMCTL_set_pagefault_info          1004
     uint32_t interface_version; /* XEN_DOMCTL_INTERFACE_VERSION */
     domid_t  domain;
     union {
@@ -1068,6 +1081,7 @@ struct xen_domctl {
         struct xen_domctl_cacheflush        cacheflush;
         struct xen_domctl_gdbsx_pauseunp_vcpu gdbsx_pauseunp_vcpu;
         struct xen_domctl_gdbsx_domstatus   gdbsx_domstatus;
+        struct xen_domctl_set_pagefault_info set_pagefault_info;
         uint8_t                             pad[128];
     } u;
 };
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index f920e1a..fe78a9a 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -447,6 +447,13 @@ struct domain
     nodemask_t node_affinity;
     unsigned int last_alloc_node;
     spinlock_t node_affinity_lock;
+
+    /* Memory introspection page fault injection data. */
+    struct {
+        uint64_t address_space;
+        uint64_t virtual_address;
+        uint32_t write_access;
+    } fault_info;
 };
 
 struct domain_setup_info
-- 
1.7.9.5


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel