diff --git a/hw/pci/msi.c b/hw/pci/msi.c
index f9c0484..3998725 100644
--- a/hw/pci/msi.c
+++ b/hw/pci/msi.c
@@ -19,6 +19,7 @@
  */
 
 #include "hw/pci/msi.h"
+#include "hw/xen/xen.h"
 #include "qemu/range.h"
 
 /* PCI_MSI_ADDRESS_LO */
@@ -253,13 +254,19 @@ void msi_reset(PCIDevice *dev)
 static bool msi_is_masked(const PCIDevice *dev, unsigned int vector)
 {
     uint16_t flags = pci_get_word(dev->config + msi_flags_off(dev));
-    uint32_t mask;
+    uint32_t mask, data;
+    bool msi64bit = flags & PCI_MSI_FLAGS_64BIT;
     assert(vector < PCI_MSI_VECTORS_MAX);
 
     if (!(flags & PCI_MSI_FLAGS_MASKBIT)) {
         return false;
     }
 
+    data = pci_get_word(dev->config + msi_data_off(dev, msi64bit));
+    if (xen_is_pirq_msi(data)) {
+        return false;
+    }
+
     mask = pci_get_long(dev->config +
                         msi_mask_off(dev, flags & PCI_MSI_FLAGS_64BIT));
     return mask & (1U << vector);
diff --git a/hw/pci/msix.c b/hw/pci/msix.c
index 7716bf3..96281c2 100644
--- a/hw/pci/msix.c
+++ b/hw/pci/msix.c
@@ -18,6 +18,7 @@
 #include "hw/pci/msi.h"
 #include "hw/pci/msix.h"
 #include "hw/pci/pci.h"
+#include "hw/xen/xen.h"
 #include "qemu/range.h"
 
 #define MSIX_CAP_LENGTH 12
@@ -77,8 +78,15 @@ static void msix_clr_pending(PCIDevice *dev, int vector)
 
 static bool msix_vector_masked(PCIDevice *dev, unsigned int vector, bool fmask)
 {
-    unsigned offset = vector * PCI_MSIX_ENTRY_SIZE + PCI_MSIX_ENTRY_VECTOR_CTRL;
-    return fmask || dev->msix_table[offset] & PCI_MSIX_ENTRY_CTRL_MASKBIT;
+    unsigned offset = vector * PCI_MSIX_ENTRY_SIZE;
+    uint32_t *data = (uint32_t *)&dev->msix_table[offset + PCI_MSIX_ENTRY_DATA];
+    /* MSIs on Xen can be remapped into pirqs. In those cases, masking
+     * and unmasking go through the PV evtchn path. */
+    if (xen_is_pirq_msi(*data)) {
+        return false;
+    }
+    return fmask || dev->msix_table[offset + PCI_MSIX_ENTRY_VECTOR_CTRL] &
+        PCI_MSIX_ENTRY_CTRL_MASKBIT;
 }
 
 bool msix_is_masked(PCIDevice *dev, unsigned int vector)
diff --git a/hw/xen/xen_pt_msi.c b/hw/xen/xen_pt_msi.c
index 82de2bc..375707e 100644
--- a/hw/xen/xen_pt_msi.c
+++ b/hw/xen/xen_pt_msi.c
@@ -113,9 +113,7 @@ static int msi_msix_setup(XenPCIPassthroughState *s,
 
     assert((!is_msix && msix_entry == 0) || is_msix);
 
-    if (gvec == 0) {
-        /* if gvec is 0, the guest is asking for a particular pirq that
-         * is passed as dest_id */
+    if (xen_is_pirq_msi(data)) {
         *ppirq = msi_ext_dest_id(addr >> 32) | msi_dest_id(addr);
         if (!*ppirq) {
             /* this probably identifies an misconfiguration of the guest,
diff --git a/include/hw/xen/xen.h b/include/hw/xen/xen.h
index 4356af4..b15b2f5 100644
--- a/include/hw/xen/xen.h
+++ b/include/hw/xen/xen.h
@@ -32,6 +32,7 @@ int xen_pci_slot_get_pirq(PCIDevice *pci_dev, int irq_num);
 void xen_piix3_set_irq(void *opaque, int irq_num, int level);
 void xen_piix_pci_write_config_client(uint32_t address, uint32_t val, int len);
 void xen_hvm_inject_msi(uint64_t addr, uint32_t data);
+int xen_is_pirq_msi(uint32_t msi_data);
 
 qemu_irq *xen_interrupt_controller_init(void);
 
diff --git a/xen-hvm-stub.c b/xen-hvm-stub.c
index 46867d8..ce22a82 100644
--- a/xen-hvm-stub.c
+++ b/xen-hvm-stub.c
@@ -30,6 +30,11 @@ void xen_hvm_inject_msi(uint64_t addr, uint32_t data)
 {
 }
 
+int xen_is_pirq_msi(uint32_t msi_data)
+{
+    return 0;
+}
+
 void xen_ram_alloc(ram_addr_t ram_addr, ram_addr_t size, MemoryRegion *mr)
 {
 }
diff --git a/xen-hvm.c b/xen-hvm.c
index 3371c4e..21dd301 100644
--- a/xen-hvm.c
+++ b/xen-hvm.c
@@ -12,6 +12,7 @@
 
 #include "hw/pci/pci.h"
 #include "hw/i386/pc.h"
+#include "hw/i386/apic-msidef.h"
 #include "hw/xen/xen_common.h"
 #include "hw/xen/xen_backend.h"
 #include "qmp-commands.h"
@@ -156,6 +157,14 @@ void xen_piix_pci_write_config_client(uint32_t address, uint32_t val, int len)
     }
 }
 
+int xen_is_pirq_msi(uint32_t msi_data)
+{
+    /* If vector is 0, the msi is remapped into a pirq, passed as
+     * dest_id.
+     */
+    return ((msi_data & MSI_DATA_VECTOR_MASK) >> MSI_DATA_VECTOR_SHIFT) == 0;
+}
+
 void xen_hvm_inject_msi(uint64_t addr, uint32_t data)
 {
     xen_xc_hvm_inject_msi(xen_xc, xen_domid, addr, data);
