[Xen-changelog] [xen stable-4.2] x86: don't drop guest visible state updates when 64-bit PV guest is in user mode

[patchbot@xxxxxxx]

commit 0620cc886eef9018d2b2a5fcdc641be70b5ac54b
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Thu Feb 20 08:41:22 2014 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Feb 20 08:41:22 2014 +0100

    x86: don't drop guest visible state updates when 64-bit PV guest is in user 
mode
    
    Since 64-bit PV uses separate kernel and user mode page tables, kernel
    addresses (as usually provided via VCPUOP_register_runstate_memory_area)
    aren't necessarily accessible when the respective updating occurs. Add
    logic for toggle_guest_mode() to take care of this (if necessary) the
    next time the vCPU switches to kernel mode.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    master commit: 231d7f4098c8ac9cdb78f18fcb820d8618c8b0c2
    master date: 2014-01-23 10:30:08 +0100
---
 xen/arch/x86/domain.c        |   24 ++++++++++++++++--------
 xen/arch/x86/x86_64/traps.c  |    7 +++++++
 xen/include/asm-x86/domain.h |    5 +++++
 3 files changed, 28 insertions(+), 8 deletions(-)

diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index ecba304..2dfea87 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -1563,10 +1563,10 @@ static void paravirt_ctxt_switch_to(struct vcpu *v)
 }
 
 /* Update per-VCPU guest runstate shared memory area (if registered). */
-static void update_runstate_area(struct vcpu *v)
+bool_t update_runstate_area(const struct vcpu *v)
 {
     if ( guest_handle_is_null(runstate_guest(v)) )
-        return;
+        return 1;
 
 #ifdef CONFIG_COMPAT
     if ( has_32bit_shinfo(v->domain) )
@@ -1575,11 +1575,19 @@ static void update_runstate_area(struct vcpu *v)
 
         XLAT_vcpu_runstate_info(&info, &v->runstate);
         __copy_to_guest(v->runstate_guest.compat, &info, 1);
-        return;
+        return 1;
     }
 #endif
 
-    __copy_to_guest(runstate_guest(v), &v->runstate, 1);
+    return __copy_to_guest(runstate_guest(v), &v->runstate, 1) !=
+           sizeof(v->runstate);
+}
+
+static void _update_runstate_area(struct vcpu *v)
+{
+    if ( !update_runstate_area(v) && !is_hvm_vcpu(v) &&
+         !(v->arch.flags & TF_kernel_mode) )
+        v->arch.pv_vcpu.need_update_runstate_area = 1;
 }
 
 static inline int need_full_gdt(struct vcpu *v)
@@ -1684,8 +1692,8 @@ void context_switch(struct vcpu *prev, struct vcpu *next)
         flush_tlb_mask(&dirty_mask);
     }
 
-    if (prev != next)
-        update_runstate_area(prev);
+    if ( prev != next )
+        _update_runstate_area(prev);
 
     if ( is_hvm_vcpu(prev) && !list_empty(&prev->arch.hvm_vcpu.tm_list) )
         pt_save_timer(prev);
@@ -1730,8 +1738,8 @@ void context_switch(struct vcpu *prev, struct vcpu *next)
 
     context_saved(prev);
 
-    if (prev != next)
-        update_runstate_area(next);
+    if ( prev != next )
+        _update_runstate_area(next);
 
     schedule_tail(next);
     BUG();
diff --git a/xen/arch/x86/x86_64/traps.c b/xen/arch/x86/x86_64/traps.c
index d20e528..ba1c408 100644
--- a/xen/arch/x86/x86_64/traps.c
+++ b/xen/arch/x86/x86_64/traps.c
@@ -266,6 +266,13 @@ void toggle_guest_mode(struct vcpu *v)
 #else
     write_ptbase(v);
 #endif
+
+    if ( !(v->arch.flags & TF_kernel_mode) )
+        return;
+
+    if ( v->arch.pv_vcpu.need_update_runstate_area &&
+         update_runstate_area(v) )
+        v->arch.pv_vcpu.need_update_runstate_area = 0;
 }
 
 unsigned long do_iret(void)
diff --git a/xen/include/asm-x86/domain.h b/xen/include/asm-x86/domain.h
index 9be5239..6c62c25 100644
--- a/xen/include/asm-x86/domain.h
+++ b/xen/include/asm-x86/domain.h
@@ -419,6 +419,9 @@ struct pv_vcpu
     /* Current LDT details. */
     unsigned long shadow_ldt_mapcnt;
     spinlock_t shadow_ldt_lock;
+
+    /* Deferred VA-based update state. */
+    bool_t need_update_runstate_area;
 };
 
 struct arch_vcpu
@@ -514,6 +517,8 @@ struct arch_vcpu
 #define hvm_vmx         hvm_vcpu.u.vmx
 #define hvm_svm         hvm_vcpu.u.svm
 
+bool_t update_runstate_area(const struct vcpu *);
+
 void vcpu_show_execution_state(struct vcpu *);
 void vcpu_show_registers(const struct vcpu *);
 
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.2

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