[PATCH v1 7/7] x86/vmx: switch IPT MSRs on vmentry/vmexit

[Michał Leszczyński <michal.leszczynski@xxxxxxx>]

Enable IPT when entering the VM and disable it on vmexit.
Register state is persisted using vCPU ipt_state structure.

Signed-off-by: Michal Leszczynski <michal.leszczynski@xxxxxxx>
---
 xen/arch/x86/hvm/vmx/vmx.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 97104c319e..01d9a7b584 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -3698,6 +3698,15 @@ void vmx_vmexit_handler(struct cpu_user_regs *regs)
     __vmread(GUEST_RSP,    &regs->rsp);
     __vmread(GUEST_RFLAGS, &regs->rflags);
 
+    if ( unlikely(v->arch.hvm.vmx.ipt_state) )
+    {
+        wrmsrl(MSR_IA32_RTIT_CTL, 0);
+        smp_rmb();
+
+        rdmsrl(MSR_IA32_RTIT_STATUS, v->arch.hvm.vmx.ipt_state->status);
+        rdmsrl(MSR_IA32_RTIT_OUTPUT_MASK, 
v->arch.hvm.vmx.ipt_state->output_mask);
+    }
+
     hvm_invalidate_regs_fields(regs);
 
     if ( paging_mode_hap(v->domain) )
@@ -4497,6 +4506,23 @@ bool vmx_vmenter_helper(const struct cpu_user_regs *regs)
     }
 
  out:
+    if ( unlikely(curr->arch.hvm.vmx.ipt_state) )
+    {
+        wrmsrl(MSR_IA32_RTIT_CTL, 0);
+
+        if (curr->arch.hvm.vmx.ipt_state->ctl)
+        {
+            wrmsrl(MSR_IA32_RTIT_OUTPUT_BASE, 
curr->arch.hvm.vmx.ipt_state->output_base);
+            wrmsrl(MSR_IA32_RTIT_OUTPUT_MASK, 
curr->arch.hvm.vmx.ipt_state->output_mask);
+            wrmsrl(MSR_IA32_RTIT_STATUS, curr->arch.hvm.vmx.ipt_state->status);
+
+            // MSR_IA32_RTIT_CTL is context-switched manually instead of being
+            // stored inside VMCS, as of Q2'20 only the most recent processors
+            // support such field in VMCS
+            wrmsrl(MSR_IA32_RTIT_CTL, curr->arch.hvm.vmx.ipt_state->ctl);
+        }
+    }
+
     if ( unlikely(curr->arch.hvm.vmx.lbr_flags & LBR_FIXUP_MASK) )
         lbr_fixup();
 
-- 
2.20.1