VT-d PI: disable VT-d PI when CPU-side PI isn't enabled

From the context calling pi_desc_init(), we can conclude the current
implementation of VT-d PI depends on CPU-side PI. If we enable VT-d PI
and disable CPU-side PI by disabling APICv explicitly in xen boot
command line, we would get an assertion failure.

This patch clears iommu_intpost once finding CPU-side PI won't be enabled.
It is safe for this is done before this flag starts taking effect. Also
take this chance to remove the useless check of "acknowledge interrupt on
exit", which is a minimal requirement which has been checked earlier.

Signed-off-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Kevin Tian <kevin.tian@intel.com>
master commit: e489eb6138e7efe4214a7e9ba0d21f54fc5b7d35
master date: 2017-08-10 12:32:16 +0200

diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
index 4646ecc28d0b5b6cd3766831dd3ec213a1d8bcba..8d7bd7b2267f6ddc0c68a00cac37af70226d946b 100644 (file)
--- a/xen/arch/x86/hvm/vmx/vmcs.c
+++ b/xen/arch/x86/hvm/vmx/vmcs.c
@@ -345,11 +345,19 @@ static int vmx_init_vmcs_config(void)
 
     /*
      * "Process posted interrupt" can be set only when "virtual-interrupt
-     * delivery" and "acknowledge interrupt on exit" is set
+     * delivery" and "acknowledge interrupt on exit" is set. For the latter
+     * is a minimal requirement, only check the former, which is optional.
      */
-    if ( !(_vmx_secondary_exec_control & SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY)
-          || !(_vmx_vmexit_control & VM_EXIT_ACK_INTR_ON_EXIT) )
-        _vmx_pin_based_exec_control  &= ~ PIN_BASED_POSTED_INTERRUPT;
+    if ( !(_vmx_secondary_exec_control & SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY) )
+        _vmx_pin_based_exec_control &= ~PIN_BASED_POSTED_INTERRUPT;
+
+    if ( iommu_intpost &&
+         !(_vmx_pin_based_exec_control & PIN_BASED_POSTED_INTERRUPT) )
+    {
+        printk("Intel VT-d Posted Interrupt is disabled for CPU-side Posted "
+               "Interrupt is not enabled\n");
+        iommu_intpost = 0;
+    }
 
     /* The IA32_VMX_VMFUNC MSR exists only when VMFUNC is available */
     if ( _vmx_secondary_exec_control & SECONDARY_EXEC_ENABLE_VM_FUNCTIONS )