From: David Woodhouse <dwmw@amazon.co.uk>

We should probably check if we were meant to be exposing IR, before
letting the guest turn the IRE bit on.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Peter Xu <peterx@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20220314142544.150555-3-dwmw2@infradead.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 hw/i386/intel_iommu.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index b22376a45d..d3361c8313 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -2209,6 +2209,7 @@ static void vtd_handle_gcmd_ire(IntelIOMMUState *s, bool en)
 /* Handle write to Global Command Register */
 static void vtd_handle_gcmd_write(IntelIOMMUState *s)
 {
+    X86IOMMUState *x86_iommu = X86_IOMMU_DEVICE(s);
     uint32_t status = vtd_get_long_raw(s, DMAR_GSTS_REG);
     uint32_t val = vtd_get_long_raw(s, DMAR_GCMD_REG);
     uint32_t changed = status ^ val;
@@ -2230,7 +2231,8 @@ static void vtd_handle_gcmd_write(IntelIOMMUState *s)
         /* Set/update the interrupt remapping root-table pointer */
         vtd_handle_gcmd_sirtp(s);
     }
-    if (changed & VTD_GCMD_IRE) {
+    if ((changed & VTD_GCMD_IRE) &&
+        x86_iommu_ir_supported(x86_iommu)) {
         /* Interrupt remap enable/disable */
         vtd_handle_gcmd_ire(s, val & VTD_GCMD_IRE);
     }
-- 
MST