[v4,1/2] x86/nvmx: split updating RVI from SVI in nvmx_update_apicv

Commit Message

Roger Pau Monne March 27, 2020, 12:45 p.m. UTC

Updating SVI is required when an interrupt has been injected using the
Ack on exit VMEXIT feature, so that the in service interrupt in the
GUEST_INTR_STATUS matches the vector that is signaled in
VM_EXIT_INTR_INFO.

Updating RVI however is not tied to the Ack on exit feature, as it
signals the next vector to be injected, and hence should always be
updated to the next pending vector, regardless of whether Ack on exit
is enabled.

When not using the Ack on exit feature preserve the previous vector in
SVI, so that it's not lost when RVI is updated to contain the pending
vector to inject.

Signed-off-by: Roger Pau Monné <[e-mail]>
Reviewed-by: Kevin Tian <[e-mail]>
---
Changes since v3:
 - Return early if interrupt source is not lapic.

Changes since v2:
 - Return early if the exit reason != EXTERNAL_INTERRUPT.
 - Reduce the number of vmwrites by accumulating the changes to a
   local variable which is flushed at the end of the function.
 - Attempt to preserve the exiting SVI if Ack on exit is not enabled.
---
 xen/arch/x86/hvm/vmx/vvmx.c | 35 +++++++++++++++++++++++++----------
 1 file changed, 25 insertions(+), 10 deletions(-)

Patch

diff --git a/xen/arch/x86/hvm/vmx/vvmx.c b/xen/arch/x86/hvm/vmx/vvmx.c
index 1753005c91..d63f417f9c 100644
--- a/xen/arch/x86/hvm/vmx/vvmx.c
+++ b/xen/arch/x86/hvm/vmx/vvmx.c
@@ -1384,28 +1384,43 @@  static void nvmx_update_apicv(struct vcpu *v)
     struct nestedvmx *nvmx = &vcpu_2_nvmx(v);
     unsigned long reason = get_vvmcs(v, VM_EXIT_REASON);
     unsigned long intr_info = get_vvmcs(v, VM_EXIT_INTR_INFO);
+    unsigned long status;
+    int rvi;
 
-    if ( reason == EXIT_REASON_EXTERNAL_INTERRUPT &&
-         nvmx->intr.source == hvm_intsrc_lapic &&
-         (intr_info & INTR_INFO_VALID_MASK) )
+    if ( reason != EXIT_REASON_EXTERNAL_INTERRUPT ||
+         nvmx->intr.source != hvm_intsrc_lapic )
+        return;
+
+    if ( intr_info & INTR_INFO_VALID_MASK )
     {
-        uint16_t status;
-        uint32_t rvi, ppr;
-        uint32_t vector = intr_info & 0xff;
+        uint32_t ppr;
+        unsigned int vector = intr_info & INTR_INFO_VECTOR_MASK;
         struct vlapic *vlapic = vcpu_vlapic(v);
 
+        /*
+         * Update SVI to record the current in service interrupt that's
+         * signaled in EXIT_INTR_INFO.
+         */
         vlapic_ack_pending_irq(v, vector, 1);
 
         ppr = vlapic_set_ppr(vlapic);
         WARN_ON((ppr & 0xf0) != (vector & 0xf0));
 
         status = vector << VMX_GUEST_INTR_STATUS_SVI_OFFSET;
-        rvi = vlapic_has_pending_irq(v);
-        if ( rvi != -1 )
-            status |= rvi & VMX_GUEST_INTR_STATUS_SUBFIELD_BITMASK;
+    }
+    else
+       /* Keep previous SVI if there's any. */
+       __vmread(GUEST_INTR_STATUS, &status);
 
-        __vmwrite(GUEST_INTR_STATUS, status);
+    rvi = vlapic_has_pending_irq(v);
+    if ( rvi != -1 )
+    {
+        status &= ~VMX_GUEST_INTR_STATUS_SUBFIELD_BITMASK;
+        status |= rvi & VMX_GUEST_INTR_STATUS_SUBFIELD_BITMASK;
     }
+
+    if ( status )
+        __vmwrite(GUEST_INTR_STATUS, status);
 }
 
 static void virtual_vmexit(struct cpu_user_regs *regs)