[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Xen-changelog] [xen staging] x86/mm: suppress vm_events caused by page-walks



commit c5387c4d75602dbb2f0d3d961a5c4b8faf3873db
Author:     Alexandru Isaila <aisaila@xxxxxxxxxxxxxxx>
AuthorDate: Thu Jul 5 15:25:20 2018 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Jul 5 15:25:20 2018 +0200

    x86/mm: suppress vm_events caused by page-walks
    
    This patch is adding a way to enable/disable inguest pagefault
    events. It introduces the xc_monitor_inguest_pagefault function
    and adds the inguest_pagefault_disabled in the monitor structure.
    This is needed by the introspection so it will only get gla
    faults and not get spammed with other faults.
    In p2m_mem_access_check() we emulate so no event will get sent.
    
    Signed-off-by: Alexandru Isaila <aisaila@xxxxxxxxxxxxxxx>
    Acked-by: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>
    Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 tools/libxc/include/xenctrl.h       |  7 +++++++
 tools/libxc/xc_monitor.c            | 14 ++++++++++++++
 tools/tests/xen-access/xen-access.c | 36 +++++++++++++++++++++++++++++++++++-
 xen/arch/x86/mm/mem_access.c        |  9 +++++++++
 xen/arch/x86/monitor.c              | 13 +++++++++++++
 xen/include/asm-x86/domain.h        |  5 +++++
 xen/include/asm-x86/monitor.h       |  3 ++-
 xen/include/public/domctl.h         |  2 ++
 8 files changed, 87 insertions(+), 2 deletions(-)

diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
index e8285dbb5f..580d2cdb06 100644
--- a/tools/libxc/include/xenctrl.h
+++ b/tools/libxc/include/xenctrl.h
@@ -2047,6 +2047,13 @@ int xc_monitor_descriptor_access(xc_interface *xch, 
uint32_t domain_id,
                                  bool enable);
 int xc_monitor_guest_request(xc_interface *xch, uint32_t domain_id,
                              bool enable, bool sync, bool allow_userspace);
+/*
+ * Disables page-walk mem_access events by emulating. If the
+ * emulation can not be performed then a VM_EVENT_REASON_EMUL_UNIMPLEMENTED
+ * event will be issued.
+ */
+int xc_monitor_inguest_pagefault(xc_interface *xch, uint32_t domain_id,
+                                 bool disable);
 int xc_monitor_debug_exceptions(xc_interface *xch, uint32_t domain_id,
                                 bool enable, bool sync);
 int xc_monitor_cpuid(xc_interface *xch, uint32_t domain_id, bool enable);
diff --git a/tools/libxc/xc_monitor.c b/tools/libxc/xc_monitor.c
index 0233b87b3f..4ac823e775 100644
--- a/tools/libxc/xc_monitor.c
+++ b/tools/libxc/xc_monitor.c
@@ -163,6 +163,20 @@ int xc_monitor_guest_request(xc_interface *xch, uint32_t 
domain_id, bool enable,
     return do_domctl(xch, &domctl);
 }
 
+int xc_monitor_inguest_pagefault(xc_interface *xch, uint32_t domain_id,
+                                bool disable)
+{
+    DECLARE_DOMCTL;
+
+    domctl.cmd = XEN_DOMCTL_monitor_op;
+    domctl.domain = domain_id;
+    domctl.u.monitor_op.op = disable ? XEN_DOMCTL_MONITOR_OP_ENABLE
+                                    : XEN_DOMCTL_MONITOR_OP_DISABLE;
+    domctl.u.monitor_op.event = XEN_DOMCTL_MONITOR_EVENT_INGUEST_PAGEFAULT;
+
+    return do_domctl(xch, &domctl);
+}
+
 int xc_monitor_emulate_each_rep(xc_interface *xch, uint32_t domain_id,
                                 bool enable)
 {
diff --git a/tools/tests/xen-access/xen-access.c 
b/tools/tests/xen-access/xen-access.c
index 8c32bfbc3f..6aaee16d67 100644
--- a/tools/tests/xen-access/xen-access.c
+++ b/tools/tests/xen-access/xen-access.c
@@ -360,7 +360,7 @@ void usage(char* progname)
 {
     fprintf(stderr, "Usage: %s [-m] <domain_id> write|exec", progname);
 #if defined(__i386__) || defined(__x86_64__)
-            fprintf(stderr, 
"|breakpoint|altp2m_write|altp2m_exec|debug|cpuid|desc_access|write_ctrlreg_cr4");
+            fprintf(stderr, 
"|breakpoint|altp2m_write|altp2m_exec|debug|cpuid|desc_access|write_ctrlreg_cr4|altp2m_write_no_gpt");
 #elif defined(__arm__) || defined(__aarch64__)
             fprintf(stderr, "|privcall");
 #endif
@@ -393,6 +393,7 @@ int main(int argc, char *argv[])
     int cpuid = 0;
     int desc_access = 0;
     int write_ctrlreg_cr4 = 0;
+    int altp2m_write_no_gpt = 0;
     uint16_t altp2m_view_id = 0;
 
     char* progname = argv[0];
@@ -451,6 +452,13 @@ int main(int argc, char *argv[])
         altp2m = 1;
         memaccess = 1;
     }
+    else if ( !strcmp(argv[0], "altp2m_write_no_gpt") )
+    {
+        default_access = XENMEM_access_rw;
+        altp2m_write_no_gpt = 1;
+        memaccess = 1;
+        altp2m = 1;
+    }
     else if ( !strcmp(argv[0], "debug") )
     {
         debug = 1;
@@ -511,6 +519,22 @@ int main(int argc, char *argv[])
         xen_pfn_t gfn = 0;
         unsigned long perm_set = 0;
 
+        if( altp2m_write_no_gpt )
+        {
+            rc = xc_monitor_inguest_pagefault(xch, domain_id, 1);
+            if ( rc < 0 )
+            {
+                ERROR("Error %d setting inguest pagefault\n", rc);
+                goto exit;
+            }
+            rc = xc_monitor_emul_unimplemented(xch, domain_id, 1);
+            if ( rc < 0 )
+            {
+                ERROR("Error %d failed to enable emul unimplemented\n", rc);
+                goto exit;
+            }
+        }
+
         rc = xc_altp2m_set_domain_state( xch, domain_id, 1 );
         if ( rc < 0 )
         {
@@ -857,6 +881,16 @@ int main(int argc, char *argv[])
                        req.u.write_ctrlreg.old_value,
                        req.u.write_ctrlreg.new_value);
                 break;
+            case VM_EVENT_REASON_EMUL_UNIMPLEMENTED:
+                if ( altp2m_write_no_gpt && req.flags & 
VM_EVENT_FLAG_ALTERNATE_P2M )
+                {
+                    DPRINTF("\tSwitching back to default view!\n");
+
+                    rsp.flags |= (VM_EVENT_FLAG_ALTERNATE_P2M |
+                                  VM_EVENT_FLAG_TOGGLE_SINGLESTEP);
+                    rsp.altp2m_idx = 0;
+                }
+                break;
             default:
                 fprintf(stderr, "UNKNOWN REASON CODE %d\n", req.reason);
             }
diff --git a/xen/arch/x86/mm/mem_access.c b/xen/arch/x86/mm/mem_access.c
index c0cd0174cf..febe38d8df 100644
--- a/xen/arch/x86/mm/mem_access.c
+++ b/xen/arch/x86/mm/mem_access.c
@@ -28,6 +28,7 @@
 #include <public/vm_event.h>
 #include <asm/p2m.h>
 #include <asm/altp2m.h>
+#include <asm/hvm/emulate.h>
 #include <asm/vm_event.h>
 
 #include "mm-locks.h"
@@ -207,6 +208,14 @@ bool p2m_mem_access_check(paddr_t gpa, unsigned long gla,
             return true;
         }
     }
+    if ( vm_event_check_ring(d->vm_event_monitor) &&
+         d->arch.monitor.inguest_pagefault_disabled &&
+         npfec.kind != npfec_kind_with_gla ) /* don't send a mem_event */
+    {
+        hvm_emulate_one_vm_event(EMUL_KIND_NORMAL, TRAP_invalid_op, 
X86_EVENT_NO_EC);
+
+        return true;
+    }
 
     *req_ptr = NULL;
     req = xzalloc(vm_event_request_t);
diff --git a/xen/arch/x86/monitor.c b/xen/arch/x86/monitor.c
index 3fb6531f6e..3c42e21906 100644
--- a/xen/arch/x86/monitor.c
+++ b/xen/arch/x86/monitor.c
@@ -242,6 +242,19 @@ int arch_monitor_domctl_event(struct domain *d,
         break;
     }
 
+    case XEN_DOMCTL_MONITOR_EVENT_INGUEST_PAGEFAULT:
+    {
+        bool old_status = ad->monitor.inguest_pagefault_disabled;
+
+        if ( unlikely(old_status == requested_status) )
+            return -EEXIST;
+
+        domain_pause(d);
+        ad->monitor.inguest_pagefault_disabled = requested_status;
+        domain_unpause(d);
+        break;
+    }
+
     case XEN_DOMCTL_MONITOR_EVENT_DESC_ACCESS:
     {
         bool old_status = ad->monitor.descriptor_access_enabled;
diff --git a/xen/include/asm-x86/domain.h b/xen/include/asm-x86/domain.h
index e0d413c7de..5a6332c2b7 100644
--- a/xen/include/asm-x86/domain.h
+++ b/xen/include/asm-x86/domain.h
@@ -417,6 +417,11 @@ struct arch_domain
         unsigned int descriptor_access_enabled                             : 1;
         unsigned int guest_request_userspace_enabled                       : 1;
         unsigned int emul_unimplemented_enabled                            : 1;
+        /*
+         * By default all events are sent.
+         * This is used to filter out pagefaults.
+         */
+        unsigned int inguest_pagefault_disabled                            : 1;
         struct monitor_msr_bitmap *msr_bitmap;
         uint64_t write_ctrlreg_mask[4];
     } monitor;
diff --git a/xen/include/asm-x86/monitor.h b/xen/include/asm-x86/monitor.h
index 4f1c7ffe0a..49889033f4 100644
--- a/xen/include/asm-x86/monitor.h
+++ b/xen/include/asm-x86/monitor.h
@@ -84,7 +84,8 @@ static inline uint32_t arch_monitor_get_capabilities(struct 
domain *d)
                     (1U << XEN_DOMCTL_MONITOR_EVENT_CPUID) |
                     (1U << XEN_DOMCTL_MONITOR_EVENT_DEBUG_EXCEPTION) |
                     (1U << XEN_DOMCTL_MONITOR_EVENT_WRITE_CTRLREG) |
-                    (1U << XEN_DOMCTL_MONITOR_EVENT_EMUL_UNIMPLEMENTED));
+                    (1U << XEN_DOMCTL_MONITOR_EVENT_EMUL_UNIMPLEMENTED) |
+                    (1U << XEN_DOMCTL_MONITOR_EVENT_INGUEST_PAGEFAULT));
 
     if ( hvm_is_singlestep_supported() )
         capabilities |= (1U << XEN_DOMCTL_MONITOR_EVENT_SINGLESTEP);
diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
index 0535da81c6..5c3916caaf 100644
--- a/xen/include/public/domctl.h
+++ b/xen/include/public/domctl.h
@@ -998,6 +998,8 @@ struct xen_domctl_psr_cmt_op {
 #define XEN_DOMCTL_MONITOR_EVENT_INTERRUPT             8
 #define XEN_DOMCTL_MONITOR_EVENT_DESC_ACCESS           9
 #define XEN_DOMCTL_MONITOR_EVENT_EMUL_UNIMPLEMENTED    10
+/* Enabled by default */
+#define XEN_DOMCTL_MONITOR_EVENT_INGUEST_PAGEFAULT     11
 
 struct xen_domctl_monitor_op {
     uint32_t op; /* XEN_DOMCTL_MONITOR_OP_* */
--
generated by git-patchbot for /home/xen/git/xen.git#staging

_______________________________________________
Xen-changelog mailing list
Xen-changelog@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/xen-changelog

 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.