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 69ba36ee150ab128fe4b397aee151a2fb6a1fdbf..e324c8262c0f3896d8aa6c49af26bd6e7bb68c36 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 5c49bfc30493d076b23649c1b0d135cf2f729124..9902a56f905c19afd84640381433253f45fa3640 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 688518aefc3cc9870bffd0859d314e7fed11af59..c2f939ae65e6043c004fc54f7e4d724282eacc10 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 0f3942e5310ee554bcecc9b5e9465d2536260c09..1c49bfea38b00505ece9297036f2bc891ddce39a 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-hvm-stub.c b/xen-hvm-stub.c
index 2d98696e72ba12bbbb2a6a317e1b372b244ccadf..d2969aa66f278b6c23c18e5fca7a8821d9b5b98c 100644 (file)
--- a/xen-hvm-stub.c
+++ b/xen-hvm-stub.c
@@ -34,6 +34,11 @@ 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)
 {
 }

diff --git a/xen-hvm.c b/xen-hvm.c
index 5c69a8dc707ba0924c20cdc94824563a633f0c66..583efc0e10840511a3694821c5de5ed1d45b2b09 100644 (file)
--- 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"
@@ -133,6 +134,14 @@ 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);