fix MSI injection on Xen

On Xen MSIs can be remapped into pirqs, which are a type of event
channels. It's mostly for the benefit of PCI passthrough devices, to
avoid the overhead of interacting with the emulated lapic.

However remapping interrupts and MSIs is also supported for emulated
devices, such as the e1000 and virtio-net.

When an interrupt or an MSI is remapped into a pirq, masking and
unmasking is done by masking and unmasking the event channel. The
masking bit on the PCI config space or MSI-X table should be ignored,
but it isn't at the moment.

As a consequence emulated devices which use MSI or MSI-X, such as
virtio-net, don't work properly (the guest doesn't receive any
notifications). The mechanism was working properly when xen_apic was
introduced, but I haven't narrowed down which commit in particular is
causing the regression.

Fix the issue by ignoring the masking bit for MSI and MSI-X which have
been remapped into pirqs.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/hw/pci/msi.c b/hw/pci/msi.c
index 74fc31a997aa49108ea7e066cba80530df15085b..9f46e65bebf9a9e42abe189cc860deee774c755c 100644 (file)
--- 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 3430770f33cd9e43ecca0de8746d15234d65e25a..828509bb0279b5bdeb6ed962a92c73e5647b7c96 100644 (file)
--- 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 76660e5e1e70f7e120f61ccab6e981f1d619fe11..587cfc7fb6edabe8aae8c730299a07b387c5da20 100644 (file)
--- a/hw/xen/xen_pt_msi.c
+++ b/hw/xen/xen_pt_msi.c
@@ -103,9 +103,7 @@ 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 e1f88bf9cf8f343733f1f17df76e0f006e712cdf..87fe0dc3911ca55198b7e6cadc43a9d5834f07d0 100644 (file)
--- a/include/hw/xen/xen.h
+++ b/include/hw/xen/xen.h
@@ -33,6 +33,7 @@ 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);
 void xen_cmos_set_s3_resume(void *opaque, int irq, int level);
+int xen_is_pirq_msi(uint32_t msi_data);
 
 qemu_irq *xen_interrupt_controller_init(void);
 

diff --git a/xen-all.c b/xen-all.c
index 0b4d9342426b3d95a7a0b17e807fde6c2bc031e8..984c34613cc1eae09cf1c240dedc09d3d09c7405 100644 (file)
--- a/xen-all.c
+++ b/xen-all.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"
@@ -131,6 +132,14 @@ 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);

diff --git a/xen-stub.c b/xen-stub.c
index ad189a6df8c276c2ff77aee0d3581b2a0ea24d58..e78e1513e5280b6c1a4ca26754da5b825ff7d96a 100644 (file)
--- a/xen-stub.c
+++ b/xen-stub.c
@@ -38,6 +38,11 @@ void xen_cmos_set_s3_resume(void *opaque, int irq, int level)
 {
 }
 
+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)
 {
 }