[Xen-devel] [PATCH v2] x86/vmx: correctly gather gs_shadow value for current vCPU

[Tamas K Lengyel <tamas@xxxxxxxxxxxxx>]

Currently the gs_shadow value is only cached when the vCPU is being scheduled
out by Xen. Reporting this (usually) stale value through vm_event is incorrect,
since it doesn't represent the actual state of the vCPU at the time the event
was recorded. This prevents vm_event subscribers from correctly finding kernel
structures in the guest when it is trapped while in ring3.

Refresh shadow_gs value when the context being saved is for the current vCPU.

Signed-off-by: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>
Cc: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
Cc: Jun Nakajima <jun.nakajima@xxxxxxxxx>
Cc: Kevin Tian <kevin.tian@xxxxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
Cc: Roger Pau Monne <roger.pau@xxxxxxxxxx>
---
v2: move fix to hvm so vm_event doesn't have to know specifics
---
 xen/arch/x86/hvm/vmx/vmx.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 283eb7b34d..5154ecc2a8 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -779,12 +779,17 @@ static void vmx_load_cpu_state(struct vcpu *v, struct 
hvm_hw_cpu *data)
 
 static void vmx_save_vmcs_ctxt(struct vcpu *v, struct hvm_hw_cpu *ctxt)
 {
+    if ( v == current )
+        vmx_save_guest_msrs(v);
+
     vmx_save_cpu_state(v, ctxt);
     vmx_vmcs_save(v, ctxt);
 }
 
 static int vmx_load_vmcs_ctxt(struct vcpu *v, struct hvm_hw_cpu *ctxt)
 {
+    ASSERT(v != current);
+
     vmx_load_cpu_state(v, ctxt);
 
     if ( vmx_vmcs_restore(v, ctxt) )
-- 
2.20.1


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel