[Xen-devel] [RFC v2 12/15] vmx: Properly handle notification event when vCPU is running

[Feng Wu <feng.wu@xxxxxxxxx>]

When a vCPU is running in Root mode and a notification event
has been injected to it. we need to set VCPU_KICK_SOFTIRQ for
the current cpu, so the pending interrupt in PIRR will be
synced to vIRR before VM-Exit in time.

Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx>
---
 xen/arch/x86/hvm/vmx/vmx.c        | 55 ++++++++++++++++++++++++++++++++++++++-
 xen/include/asm-x86/hvm/vmx/vmx.h |  1 +
 2 files changed, 55 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 0e71d7e..556a584 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -1839,7 +1839,7 @@ const struct hvm_function_table * __init start_vmx(void)
 
     if ( cpu_has_vmx_posted_intr_processing )
     {
-        alloc_direct_apic_vector(&posted_intr_vector, event_check_interrupt);
+        alloc_direct_apic_vector(&posted_intr_vector, 
pi_notification_interrupt);
 
         if ( iommu_intpost )
             alloc_direct_apic_vector(&pi_wakeup_vector, pi_wakeup_interrupt);
@@ -3293,6 +3293,59 @@ void pi_wakeup_interrupt(struct cpu_user_regs *regs)
 }
 
 /*
+ * Handle VT-d posted-interrupt when VCPU is running.
+ */
+
+void pi_notification_interrupt(struct cpu_user_regs *regs)
+{
+    /*
+     * We get here when a vCPU is running in root-mode
+     * (such as via hypercall, or any other reasons which
+     * can result in VM-Exit), and before vCPU is back to
+     * non-root, external interrupts from an assigned
+     * device happen and a notification event is delivered
+     * to this logical CPU.
+     *
+     * we need to set VCPU_KICK_SOFTIRQ for the current
+     * cpu, just like __vmx_deliver_posted_interrupt().
+     *
+     * So the pending interrupt in PIRR will be synced to
+     * vIRR before VM-Exit in time.
+     *
+     * Please refer to the following code fragments from
+     * xen/arch/x86/hvm/vmx/entry.S:
+     *
+     * .Lvmx_do_vmentry
+     *
+     *  ......
+     *  point 1
+     *
+     *  cmp  %ecx,(%rdx,%rax,1)
+     *  jnz  .Lvmx_process_softirqs
+     *
+     *  ......
+     *
+     *  je   .Lvmx_launch
+     *
+     *  ......
+     *
+     * .Lvmx_process_softirqs:
+     *  sti
+     *  call do_softirq
+     *  jmp  .Lvmx_do_vmentry
+     *
+     *  If VT-d engine issues a notification event at
+     *  point 1 above, it cannot be delivered to the guest
+     *  during this VM-entry without raising the softirq
+     *  in this notification handler.
+     */
+    raise_softirq(VCPU_KICK_SOFTIRQ);
+
+    ack_APIC_irq();
+    this_cpu(irq_count)++;
+}
+
+/*
  * Local variables:
  * mode: C
  * c-file-style: "BSD"
diff --git a/xen/include/asm-x86/hvm/vmx/vmx.h 
b/xen/include/asm-x86/hvm/vmx/vmx.h
index 3adf776..89c0f56 100644
--- a/xen/include/asm-x86/hvm/vmx/vmx.h
+++ b/xen/include/asm-x86/hvm/vmx/vmx.h
@@ -554,6 +554,7 @@ void free_p2m_hap_data(struct p2m_domain *p2m);
 void p2m_init_hap_data(struct p2m_domain *p2m);
 
 void pi_wakeup_interrupt(struct cpu_user_regs *regs);
+void pi_notification_interrupt(struct cpu_user_regs *regs);
 
 /* EPT violation qualifications definitions */
 #define _EPT_READ_VIOLATION         0
-- 
2.1.0


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