[Qemu-devel] [PATCH qemu] RFC: vfio-pci: Allow mmap of MSIX BAR

[Alexey Kardashevskiy <aik@ozlabs.ru>]

This makes use of a new VFIO_REGION_INFO_CAP_MSIX_MAPPABLE capability
which tells that a region with MSIX data can be mapped entirely, i.e.
the VFIO PCI driver won't prevent MSIX vectors area from being mapped.

This adds a "msix-no-mmap" property to the vfio-pci device, it is "true"
by default and "false" for pseries-2.12+ machines.

This requites kernel's "vfio-pci: Allow mapping MSIX BAR"
https://www.spinics.net/lists/kvm/msg160282.html

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---

This is an RFC as it requires kernel headers update which is not there yet.

I'd like to make it "msix-mmap" (without "no") but could not find a way
of enabling a device property for machine versions newer than some value.

I changed 2.11 machine just for the demonstration purpose.


---
 hw/vfio/pci.h                 |  1 +
 include/hw/vfio/vfio-common.h |  1 +
 linux-headers/linux/vfio.h    |  5 +++++
 hw/ppc/spapr.c                | 10 +++++++++-
 hw/vfio/common.c              | 15 +++++++++++++++
 hw/vfio/pci.c                 | 11 +++++++++++
 6 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/hw/vfio/pci.h b/hw/vfio/pci.h
index a8fb3b3..53912ef 100644
--- a/hw/vfio/pci.h
+++ b/hw/vfio/pci.h
@@ -142,6 +142,7 @@ typedef struct VFIOPCIDevice {
     bool no_kvm_intx;
     bool no_kvm_msi;
     bool no_kvm_msix;
+    bool msix_no_mmap;
 } VFIOPCIDevice;
 
 uint32_t vfio_pci_read_config(PCIDevice *pdev, uint32_t addr, int len);
diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
index f3a2ac9..927d600 100644
--- a/include/hw/vfio/vfio-common.h
+++ b/include/hw/vfio/vfio-common.h
@@ -171,6 +171,7 @@ int vfio_get_region_info(VFIODevice *vbasedev, int index,
                          struct vfio_region_info **info);
 int vfio_get_dev_region_info(VFIODevice *vbasedev, uint32_t type,
                              uint32_t subtype, struct vfio_region_info **info);
+bool vfio_is_cap_present(VFIODevice *vbasedev, uint16_t cap_type, int region);
 #endif
 extern const MemoryListener vfio_prereg_listener;
 
diff --git a/linux-headers/linux/vfio.h b/linux-headers/linux/vfio.h
index 4e7ab4c..bce9baf 100644
--- a/linux-headers/linux/vfio.h
+++ b/linux-headers/linux/vfio.h
@@ -300,6 +300,11 @@ struct vfio_region_info_cap_type {
 #define VFIO_REGION_SUBTYPE_INTEL_IGD_HOST_CFG	(2)
 #define VFIO_REGION_SUBTYPE_INTEL_IGD_LPC_CFG	(3)
 
+/*
+ * The MSIX mappable capability informs that MSIX data of a BAR can be mmapped.
+ */
+#define VFIO_REGION_INFO_CAP_MSIX_MAPPABLE	3
+
 /**
  * VFIO_DEVICE_GET_IRQ_INFO - _IOWR(VFIO_TYPE, VFIO_BASE + 9,
  *				    struct vfio_irq_info)
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 9de63f0..1dfc386 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -3742,13 +3742,21 @@ static const TypeInfo spapr_machine_info = {
 /*
  * pseries-2.11
  */
+#define SPAPR_COMPAT_2_11                                             \
+    HW_COMPAT_2_10                                                    \
+    {                                                                 \
+        .driver = "vfio-pci",                                         \
+        .property = "msix-no-mmap",                                   \
+        .value    = "on",                                             \
+    },                                                                \
+
 static void spapr_machine_2_11_instance_options(MachineState *machine)
 {
 }
 
 static void spapr_machine_2_11_class_options(MachineClass *mc)
 {
-    /* Defaults for the latest behaviour inherited from the base class */
+    SET_MACHINE_COMPAT(mc, SPAPR_COMPAT_2_11);
 }
 
 DEFINE_SPAPR_MACHINE(2_11, "2.11", true);
diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index ed7717d..593514c 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -1408,6 +1408,21 @@ int vfio_get_dev_region_info(VFIODevice *vbasedev, uint32_t type,
     return -ENODEV;
 }
 
+bool vfio_is_cap_present(VFIODevice *vbasedev, uint16_t cap_type, int region)
+{
+        struct vfio_region_info *info = NULL;
+        bool ret = false;
+
+        if (!vfio_get_region_info(vbasedev, region, &info)) {
+            if (vfio_get_region_info_cap(info, cap_type)) {
+                ret = true;
+            }
+            g_free(info);
+        }
+
+        return ret;
+}
+
 /*
  * Interfaces for IBM EEH (Enhanced Error Handling)
  */
diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index c977ee3..d9aeae8 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -1289,6 +1289,12 @@ static void vfio_pci_fixup_msix_region(VFIOPCIDevice *vdev)
     off_t start, end;
     VFIORegion *region = &vdev->bars[vdev->msix->table_bar].region;
 
+    if (!vdev->msix_no_mmap &&
+        vfio_is_cap_present(&vdev->vbasedev, VFIO_REGION_INFO_CAP_MSIX_MAPPABLE,
+                            vdev->msix->table_bar)) {
+        return;
+    }
+
     /*
      * We expect to find a single mmap covering the whole BAR, anything else
      * means it's either unsupported or already setup.
@@ -1473,6 +1479,10 @@ static int vfio_msix_setup(VFIOPCIDevice *vdev, int pos, Error **errp)
      */
     memory_region_set_enabled(&vdev->pdev.msix_pba_mmio, false);
 
+    if (!vdev->msix_no_mmap) {
+        memory_region_set_enabled(&vdev->pdev.msix_table_mmio, false);
+    }
+
     return 0;
 }
 
@@ -2986,6 +2996,7 @@ static Property vfio_pci_dev_properties[] = {
     DEFINE_PROP_BIT("x-igd-opregion", VFIOPCIDevice, features,
                     VFIO_FEATURE_ENABLE_IGD_OPREGION_BIT, false),
     DEFINE_PROP_BOOL("x-no-mmap", VFIOPCIDevice, vbasedev.no_mmap, false),
+    DEFINE_PROP_BOOL("msix-no-mmap", VFIOPCIDevice, msix_no_mmap, true),
     DEFINE_PROP_BOOL("x-no-kvm-intx", VFIOPCIDevice, no_kvm_intx, false),
     DEFINE_PROP_BOOL("x-no-kvm-msi", VFIOPCIDevice, no_kvm_msi, false),
     DEFINE_PROP_BOOL("x-no-kvm-msix", VFIOPCIDevice, no_kvm_msix, false),
-- 
2.11.0