[Xen-devel] [PATCH v2 3/4] VMX: Assign the right value to 'NDST' field in a concern case

[Feng Wu <feng.wu@xxxxxxxxx>]

Normally, in vmx_cpu_block() 'NDST' filed should have the same
value with 'dest' or 'MASK_INSR(dest, PI_xAPIC_NDST_MASK)' depending
on whether x2apic is enabled. However, in the following scenario,
'NDST' has different value:

'vcpu_block' hook gets assigned in vmx_pi_hooks_assign(), but all
other three PI hooks have not been assigned or not been excuted yet.
And during this interval, we are running in vmx_vcpu_block(), then
'NDST' may have different value.

This patch fix this concern case.

Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx>
---
 xen/arch/x86/hvm/vmx/vmx.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index b01128a..662b38d 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -146,8 +146,19 @@ static void vmx_vcpu_block(struct vcpu *v)
 
     dest = cpu_physical_id(v->processor);
 
-    ASSERT(pi_desc->ndst ==
-           (x2apic_enabled ? dest : MASK_INSR(dest, PI_xAPIC_NDST_MASK)));
+    /*
+     * Normally, 'NDST' filed should have the same value with dest or
+     * MASK_INSR(dest, PI_xAPIC_NDST_MASK) depending on whether x2apic is
+     * enabled. However, in the following scenario, 'NDST' has different
+     * value:
+     *
+     * 'vcpu_block' hook gets assigned in vmx_pi_hooks_assign(), but all
+     * other three PI hooks have not been assigned or not been excuted yet.
+     * And during this interval, we get here in this function, then 'NDST'
+     * may have different value.
+     */
+    write_atomic(&pi_desc->ndst,
+                 x2apic_enabled ? dest : MASK_INSR(dest, PI_xAPIC_NDST_MASK));
 
     write_atomic(&pi_desc->nv, pi_wakeup_vector);
 }
-- 
2.1.0


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