[PATCH v2 13/14] intel_iommu_accel: Add pasid bits size check

[Zhenzhong Duan <zhenzhong.duan@intel.com>]

If pasid bits size is bigger than host side, host could fail to emulate
all bindings in guest. Add a check to fail device plug early.

Pasid bits size should also be no more than 20 bits according to PCI spec.

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
---
 hw/i386/intel_iommu_internal.h | 1 +
 hw/i386/intel_iommu_accel.c    | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/hw/i386/intel_iommu_internal.h b/hw/i386/intel_iommu_internal.h
index f3cb6cff1c..d11064b527 100644
--- a/hw/i386/intel_iommu_internal.h
+++ b/hw/i386/intel_iommu_internal.h
@@ -196,6 +196,7 @@
 #define VTD_ECAP_SRS                (1ULL << 31)
 #define VTD_ECAP_NWFS               (1ULL << 33)
 #define VTD_ECAP_SET_PSS(x, v)      ((x)->ecap = deposit64((x)->ecap, 35, 5, v))
+#define VTD_ECAP_PSS(ecap)          extract64(ecap, 35, 5)
 #define VTD_ECAP_PASID              (1ULL << 40)
 #define VTD_ECAP_PDS                (1ULL << 42)
 #define VTD_ECAP_SMTS               (1ULL << 43)
diff --git a/hw/i386/intel_iommu_accel.c b/hw/i386/intel_iommu_accel.c
index 2fd26690b9..e73695ff83 100644
--- a/hw/i386/intel_iommu_accel.c
+++ b/hw/i386/intel_iommu_accel.c
@@ -44,6 +44,7 @@ bool vtd_check_hiod_accel(IntelIOMMUState *s, VTDHostIOMMUDevice *vtd_hiod,
     HostIOMMUDevice *hiod = vtd_hiod->hiod;
     struct HostIOMMUDeviceCaps *caps = &hiod->caps;
     struct iommu_hw_info_vtd *vtd = &caps->vendor_caps.vtd;
+    uint8_t hpasid = VTD_ECAP_PSS(vtd->ecap_reg) + 1;
     PCIBus *bus = vtd_hiod->bus;
     PCIDevice *pdev = bus->devices[vtd_hiod->devfn];
 
@@ -64,6 +65,13 @@ bool vtd_check_hiod_accel(IntelIOMMUState *s, VTDHostIOMMUDevice *vtd_hiod,
         return false;
     }
 
+    /* Only do the check when host device support PASIDs */
+    if (caps->max_pasid_log2 && s->pasid > hpasid) {
+        error_setg(errp, "PASID bits size %d > host IOMMU PASID bits size %d",
+                   s->pasid, hpasid);
+        return false;
+    }
+
     if (pci_device_get_iommu_bus_devfn(pdev, &bus, NULL, NULL)) {
         error_setg(errp, "Host device downstream to a PCI bridge is "
                    "unsupported when x-flts=on");
-- 
2.47.3