Hi Bryan,
I had a couple of unaddressed review comments still unresolved.

Jess

> On 19 Jan 2021, at 05:08, Bryan Venteicher <bry...@freebsd.org> wrote:
> 
> The branch main has been updated by bryanv:
> 
> URL: 
> https://cgit.FreeBSD.org/src/commit/?id=9da9560c4dd3556519cd391a04f0db157dc3c295
> 
> commit 9da9560c4dd3556519cd391a04f0db157dc3c295
> Author:     Bryan Venteicher <bry...@freebsd.org>
> AuthorDate: 2021-01-19 04:55:23 +0000
> Commit:     Bryan Venteicher <bry...@freebsd.org>
> CommitDate: 2021-01-19 04:55:23 +0000
> 
>    virtio: Add VirtIO PCI modern (V1) support
> 
>    Use the existing legacy PCI driver as the basis for shared code
>    between the legacy and modern PCI drivers. The existing virtio_pci
>    kernel module will contain both the legacy and modern drivers.
> 
>    Changes to the virtqueue and each device driver (network, block, etc)
>    for V1 support come in later commits.
> 
>    Update the MMIO driver to reflect the VirtIO bus method changes, but
>    the modern compliance can be improved on later.
> 
>    Note that the modern PCI driver requires bus_map_resource() to be
>    implemented, which is not the case on all archs.
> 
>    The hw.virtio.pci.transitional tunable default value is zero so
>    transitional devices will continue to be driven via the legacy
>    driver.
> 
>    Reviewed by: grehan (mentor)
>    Differential Revision: https://reviews.freebsd.org/D27856
> ---
> sys/conf/files                             |    3 +
> sys/dev/virtio/mmio/virtio_mmio.c          |   23 +-
> sys/dev/virtio/pci/virtio_pci.c            | 1297 +++++++++----------------
> sys/dev/virtio/pci/virtio_pci.h            |  173 ++--
> sys/dev/virtio/pci/virtio_pci_if.m         |   71 ++
> sys/dev/virtio/pci/virtio_pci_legacy.c     |  733 ++++++++++++++
> sys/dev/virtio/pci/virtio_pci_legacy_var.h |   78 ++
> sys/dev/virtio/pci/virtio_pci_modern.c     | 1448 ++++++++++++++++++++++++++++
> sys/dev/virtio/pci/virtio_pci_modern_var.h |  135 +++
> sys/dev/virtio/pci/virtio_pci_var.h        |   55 ++
> sys/dev/virtio/virtio.c                    |   76 +-
> sys/dev/virtio/virtio.h                    |    8 +
> sys/dev/virtio/virtio_bus_if.m             |   11 +
> sys/dev/virtio/virtio_endian.h             |  106 ++
> sys/dev/virtio/virtqueue.c                 |   10 +-
> sys/dev/virtio/virtqueue.h                 |    4 +-
> sys/modules/virtio/pci/Makefile            |    5 +-
> 17 files changed, 3292 insertions(+), 944 deletions(-)
> 
> diff --git a/sys/conf/files b/sys/conf/files
> index e641b79d9c46..79f3b7ca54e6 100644
> --- a/sys/conf/files
> +++ b/sys/conf/files
> @@ -3457,6 +3457,9 @@ dev/virtio/virtqueue.c                  optional        
> virtio
> dev/virtio/virtio_bus_if.m            optional        virtio
> dev/virtio/virtio_if.m                        optional        virtio
> dev/virtio/pci/virtio_pci.c           optional        virtio_pci
> +dev/virtio/pci/virtio_pci_if.m               optional        virtio_pci
> +dev/virtio/pci/virtio_pci_legacy.c   optional        virtio_pci
> +dev/virtio/pci/virtio_pci_modern.c   optional        virtio_pci
> dev/virtio/mmio/virtio_mmio.c         optional        virtio_mmio
> dev/virtio/mmio/virtio_mmio_acpi.c    optional        virtio_mmio acpi
> dev/virtio/mmio/virtio_mmio_fdt.c     optional        virtio_mmio fdt
> diff --git a/sys/dev/virtio/mmio/virtio_mmio.c 
> b/sys/dev/virtio/mmio/virtio_mmio.c
> index bb5d84754f09..694d2a232fdd 100644
> --- a/sys/dev/virtio/mmio/virtio_mmio.c
> +++ b/sys/dev/virtio/mmio/virtio_mmio.c
> @@ -84,7 +84,7 @@ static void vtmmio_stop(device_t);
> static void   vtmmio_poll(device_t);
> static int    vtmmio_reinit(device_t, uint64_t);
> static void   vtmmio_reinit_complete(device_t);
> -static void  vtmmio_notify_virtqueue(device_t, uint16_t);
> +static void  vtmmio_notify_virtqueue(device_t, uint16_t, bus_size_t);
> static uint8_t        vtmmio_get_status(device_t);
> static void   vtmmio_set_status(device_t, uint8_t);
> static void   vtmmio_read_dev_config(device_t, bus_size_t, void *, int);
> @@ -352,6 +352,13 @@ vtmmio_read_ivar(device_t dev, device_t child, int 
> index, uintptr_t *result)
>                */
>               *result = 0;
>               break;
> +     case VIRTIO_IVAR_MODERN:
> +             /*
> +              * There are several modern (aka MMIO v2) spec compliance
> +              * issues with this driver, but keep the status quo.
> +              */
> +             *result = sc->vtmmio_version > 1;
> +             break;
>       default:
>               return (ENOENT);
>       }
> @@ -388,6 +395,10 @@ vtmmio_negotiate_features(device_t dev, uint64_t 
> child_features)
> 
>       sc = device_get_softc(dev);
> 
> +     if (sc->vtmmio_version > 1) {
> +             child_features |= VIRTIO_F_VERSION_1;
> +     }
> +
>       vtmmio_write_config_4(sc, VIRTIO_MMIO_HOST_FEATURES_SEL, 1);
>       host_features = vtmmio_read_config_4(sc, VIRTIO_MMIO_HOST_FEATURES);
>       host_features <<= 32;
> @@ -402,7 +413,7 @@ vtmmio_negotiate_features(device_t dev, uint64_t 
> child_features)
>        * host all support.
>        */
>       features = host_features & child_features;
> -     features = virtqueue_filter_features(features);
> +     features = virtio_filter_transport_features(features);
>       sc->vtmmio_features = features;
> 
>       vtmmio_describe_features(sc, "negotiated", features);
> @@ -504,7 +515,8 @@ vtmmio_alloc_virtqueues(device_t dev, int flags, int nvqs,
>               size = vtmmio_read_config_4(sc, VIRTIO_MMIO_QUEUE_NUM_MAX);
> 
>               error = virtqueue_alloc(dev, idx, size,
> -                 VIRTIO_MMIO_VRING_ALIGN, ~(vm_paddr_t)0, info, &vq);
> +                 VIRTIO_MMIO_QUEUE_NOTIFY, VIRTIO_MMIO_VRING_ALIGN,
> +                 ~(vm_paddr_t)0, info, &vq);
>               if (error) {
>                       device_printf(dev,
>                           "cannot allocate virtqueue %d: %d\n",
> @@ -586,13 +598,14 @@ vtmmio_reinit_complete(device_t dev)
> }
> 
> static void
> -vtmmio_notify_virtqueue(device_t dev, uint16_t queue)
> +vtmmio_notify_virtqueue(device_t dev, uint16_t queue, bus_size_t offset)
> {
>       struct vtmmio_softc *sc;
> 
>       sc = device_get_softc(dev);
> +     MPASS(offset == VIRTIO_MMIO_QUEUE_NOTIFY);
> 
> -     vtmmio_write_config_4(sc, VIRTIO_MMIO_QUEUE_NOTIFY, queue);
> +     vtmmio_write_config_4(sc, offset, queue);
> }
> 
> static uint8_t
> diff --git a/sys/dev/virtio/pci/virtio_pci.c b/sys/dev/virtio/pci/virtio_pci.c
> index 05a632f526a8..4d6fa929ef19 100644
> --- a/sys/dev/virtio/pci/virtio_pci.c
> +++ b/sys/dev/virtio/pci/virtio_pci.c
> @@ -1,7 +1,7 @@
> /*-
>  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
>  *
> - * Copyright (c) 2011, Bryan Venteicher <bry...@freebsd.org>
> + * Copyright (c) 2017, Bryan Venteicher <bry...@freebsd.org>
>  * All rights reserved.
>  *
>  * Redistribution and use in source and binary forms, with or without
> @@ -26,8 +26,6 @@
>  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
>  */
> 
> -/* Driver for the VirtIO PCI interface. */
> -
> #include <sys/cdefs.h>
> __FBSDID("$FreeBSD$");
> 
> @@ -37,7 +35,6 @@ __FBSDID("$FreeBSD$");
> #include <sys/kernel.h>
> #include <sys/module.h>
> #include <sys/malloc.h>
> -#include <sys/endian.h>
> 
> #include <machine/bus.h>
> #include <machine/resource.h>
> @@ -50,369 +47,236 @@ __FBSDID("$FreeBSD$");
> #include <dev/virtio/virtio.h>
> #include <dev/virtio/virtqueue.h>
> #include <dev/virtio/pci/virtio_pci.h>
> +#include <dev/virtio/pci/virtio_pci_var.h>
> 
> -#include "virtio_bus_if.h"
> +#include "virtio_pci_if.h"
> #include "virtio_if.h"
> 
> -struct vtpci_interrupt {
> -     struct resource         *vti_irq;
> -     int                      vti_rid;
> -     void                    *vti_handler;
> -};
> -
> -struct vtpci_virtqueue {
> -     struct virtqueue        *vtv_vq;
> -     int                      vtv_no_intr;
> -};
> -
> -struct vtpci_softc {
> -     device_t                         vtpci_dev;
> -     struct resource                 *vtpci_res;
> -     struct resource                 *vtpci_msix_res;
> -     uint64_t                         vtpci_features;
> -     uint32_t                         vtpci_flags;
> -#define VTPCI_FLAG_NO_MSI            0x0001
> -#define VTPCI_FLAG_NO_MSIX           0x0002
> -#define VTPCI_FLAG_LEGACY            0x1000
> -#define VTPCI_FLAG_MSI                       0x2000
> -#define VTPCI_FLAG_MSIX                      0x4000
> -#define VTPCI_FLAG_SHARED_MSIX               0x8000
> -#define VTPCI_FLAG_ITYPE_MASK                0xF000
> -
> -     /* This "bus" will only ever have one child. */
> -     device_t                         vtpci_child_dev;
> -     struct virtio_feature_desc      *vtpci_child_feat_desc;
> -
> -     int                              vtpci_nvqs;
> -     struct vtpci_virtqueue          *vtpci_vqs;
> -
> -     /*
> -      * Ideally, each virtqueue that the driver provides a callback for will
> -      * receive its own MSIX vector. If there are not sufficient vectors
> -      * available, then attempt to have all the VQs share one vector. For
> -      * MSIX, the configuration changed notifications must be on their own
> -      * vector.
> -      *
> -      * If MSIX is not available, we will attempt to have the whole device
> -      * share one MSI vector, and then, finally, one legacy interrupt.
> -      */
> -     struct vtpci_interrupt           vtpci_device_interrupt;
> -     struct vtpci_interrupt          *vtpci_msix_vq_interrupts;
> -     int                              vtpci_nmsix_resources;
> -};
> -
> -static int   vtpci_probe(device_t);
> -static int   vtpci_attach(device_t);
> -static int   vtpci_detach(device_t);
> -static int   vtpci_suspend(device_t);
> -static int   vtpci_resume(device_t);
> -static int   vtpci_shutdown(device_t);
> -static void  vtpci_driver_added(device_t, driver_t *);
> -static void  vtpci_child_detached(device_t, device_t);
> -static int   vtpci_read_ivar(device_t, device_t, int, uintptr_t *);
> -static int   vtpci_write_ivar(device_t, device_t, int, uintptr_t);
> -
> -static uint64_t      vtpci_negotiate_features(device_t, uint64_t);
> -static int   vtpci_with_feature(device_t, uint64_t);
> -static int   vtpci_alloc_virtqueues(device_t, int, int,
> -                 struct vq_alloc_info *);
> -static int   vtpci_setup_intr(device_t, enum intr_type);
> -static void  vtpci_stop(device_t);
> -static int   vtpci_reinit(device_t, uint64_t);
> -static void  vtpci_reinit_complete(device_t);
> -static void  vtpci_notify_virtqueue(device_t, uint16_t);
> -static uint8_t       vtpci_get_status(device_t);
> -static void  vtpci_set_status(device_t, uint8_t);
> -static void  vtpci_read_dev_config(device_t, bus_size_t, void *, int);
> -static void  vtpci_write_dev_config(device_t, bus_size_t, void *, int);
> -
> -static void  vtpci_describe_features(struct vtpci_softc *, const char *,
> +static void  vtpci_describe_features(struct vtpci_common *, const char *,
>                   uint64_t);
> -static void  vtpci_probe_and_attach_child(struct vtpci_softc *);
> -
> -static int   vtpci_alloc_msix(struct vtpci_softc *, int);
> -static int   vtpci_alloc_msi(struct vtpci_softc *);
> -static int   vtpci_alloc_intr_msix_pervq(struct vtpci_softc *);
> -static int   vtpci_alloc_intr_msix_shared(struct vtpci_softc *);
> -static int   vtpci_alloc_intr_msi(struct vtpci_softc *);
> -static int   vtpci_alloc_intr_legacy(struct vtpci_softc *);
> -static int   vtpci_alloc_interrupt(struct vtpci_softc *, int, int,
> +static int   vtpci_alloc_msix(struct vtpci_common *, int);
> +static int   vtpci_alloc_msi(struct vtpci_common *);
> +static int   vtpci_alloc_intr_msix_pervq(struct vtpci_common *);
> +static int   vtpci_alloc_intr_msix_shared(struct vtpci_common *);
> +static int   vtpci_alloc_intr_msi(struct vtpci_common *);
> +static int   vtpci_alloc_intr_intx(struct vtpci_common *);
> +static int   vtpci_alloc_interrupt(struct vtpci_common *, int, int,
> +                 struct vtpci_interrupt *);
> +static void  vtpci_free_interrupt(struct vtpci_common *,
>                   struct vtpci_interrupt *);
> -static int   vtpci_alloc_intr_resources(struct vtpci_softc *);
> 
> -static int   vtpci_setup_legacy_interrupt(struct vtpci_softc *,
> +static void  vtpci_free_interrupts(struct vtpci_common *);
> +static void  vtpci_free_virtqueues(struct vtpci_common *);
> +static void  vtpci_cleanup_setup_intr_attempt(struct vtpci_common *);
> +static int   vtpci_alloc_intr_resources(struct vtpci_common *);
> +static int   vtpci_setup_intx_interrupt(struct vtpci_common *,
>                   enum intr_type);
> -static int   vtpci_setup_pervq_msix_interrupts(struct vtpci_softc *,
> +static int   vtpci_setup_pervq_msix_interrupts(struct vtpci_common *,
>                   enum intr_type);
> -static int   vtpci_setup_msix_interrupts(struct vtpci_softc *,
> +static int   vtpci_set_host_msix_vectors(struct vtpci_common *);
> +static int   vtpci_setup_msix_interrupts(struct vtpci_common *,
>                   enum intr_type);
> -static int   vtpci_setup_interrupts(struct vtpci_softc *, enum intr_type);
> -
> -static int   vtpci_register_msix_vector(struct vtpci_softc *, int,
> -                 struct vtpci_interrupt *);
> -static int   vtpci_set_host_msix_vectors(struct vtpci_softc *);
> -static int   vtpci_reinit_virtqueue(struct vtpci_softc *, int);
> -
> -static void  vtpci_free_interrupt(struct vtpci_softc *,
> -                 struct vtpci_interrupt *);
> -static void  vtpci_free_interrupts(struct vtpci_softc *);
> -static void  vtpci_free_virtqueues(struct vtpci_softc *);
> -static void  vtpci_release_child_resources(struct vtpci_softc *);
> -static void  vtpci_cleanup_setup_intr_attempt(struct vtpci_softc *);
> -static void  vtpci_reset(struct vtpci_softc *);
> -
> -static void  vtpci_select_virtqueue(struct vtpci_softc *, int);
> -
> -static void  vtpci_legacy_intr(void *);
> +static int   vtpci_setup_intrs(struct vtpci_common *, enum intr_type);
> +static int   vtpci_reinit_virtqueue(struct vtpci_common *, int);
> +static void  vtpci_intx_intr(void *);
> static int    vtpci_vq_shared_intr_filter(void *);
> static void   vtpci_vq_shared_intr(void *);
> static int    vtpci_vq_intr_filter(void *);
> static void   vtpci_vq_intr(void *);
> static void   vtpci_config_intr(void *);
> 
> -#define vtpci_setup_msi_interrupt vtpci_setup_legacy_interrupt
> -
> -#define VIRTIO_PCI_CONFIG(_sc) \
> -    VIRTIO_PCI_CONFIG_OFF((((_sc)->vtpci_flags & VTPCI_FLAG_MSIX)) != 0)
> -
> -/*
> - * I/O port read/write wrappers.
> - */
> -#define vtpci_read_config_1(sc, o)   bus_read_1((sc)->vtpci_res, (o))
> -#define vtpci_write_config_1(sc, o, v)       bus_write_1((sc)->vtpci_res, 
> (o), (v))
> +#define vtpci_setup_msi_interrupt vtpci_setup_intx_interrupt
> 
> /*
> - * Virtio-pci specifies that PCI Configuration area is guest endian. However,
> - * since PCI devices are inherently little-endian, on BE systems the bus 
> layer
> - * transparently converts it to BE. For virtio-legacy, this conversion is
> - * undesired, so an extra byte swap is required to fix it.
> + * This module contains two drivers:
> + *   - virtio_pci_legacy for pre-V1 support
> + *   - virtio_pci_modern for V1 support
>  */
> -#define vtpci_read_config_2(sc, o)      le16toh(bus_read_2((sc)->vtpci_res, 
> (o)))
> -#define vtpci_read_config_4(sc, o)      le32toh(bus_read_4((sc)->vtpci_res, 
> (o)))
> -#define vtpci_write_config_2(sc, o, v)  bus_write_2((sc)->vtpci_res, (o), 
> (htole16(v)))
> -#define vtpci_write_config_4(sc, o, v)  bus_write_4((sc)->vtpci_res, (o), 
> (htole32(v)))
> -
> -/* PCI Header LE. On BE systems the bus layer takes care of byte swapping */
> -#define vtpci_read_header_2(sc, o)      (bus_read_2((sc)->vtpci_res, (o)))
> -#define vtpci_read_header_4(sc, o)      (bus_read_4((sc)->vtpci_res, (o)))
> -#define vtpci_write_header_2(sc, o, v)  bus_write_2((sc)->vtpci_res, (o), 
> (v))
> -#define vtpci_write_header_4(sc, o, v)  bus_write_4((sc)->vtpci_res, (o), 
> (v))
> -
> -/* Tunables. */
> -static int vtpci_disable_msix = 0;
> -TUNABLE_INT("hw.virtio.pci.disable_msix", &vtpci_disable_msix);
> -
> -static device_method_t vtpci_methods[] = {
> -     /* Device interface. */
> -     DEVMETHOD(device_probe,                   vtpci_probe),
> -     DEVMETHOD(device_attach,                  vtpci_attach),
> -     DEVMETHOD(device_detach,                  vtpci_detach),
> -     DEVMETHOD(device_suspend,                 vtpci_suspend),
> -     DEVMETHOD(device_resume,                  vtpci_resume),
> -     DEVMETHOD(device_shutdown,                vtpci_shutdown),
> -
> -     /* Bus interface. */
> -     DEVMETHOD(bus_driver_added,               vtpci_driver_added),
> -     DEVMETHOD(bus_child_detached,             vtpci_child_detached),
> -     DEVMETHOD(bus_child_pnpinfo_str,          virtio_child_pnpinfo_str),
> -     DEVMETHOD(bus_read_ivar,                  vtpci_read_ivar),
> -     DEVMETHOD(bus_write_ivar,                 vtpci_write_ivar),
> -
> -     /* VirtIO bus interface. */
> -     DEVMETHOD(virtio_bus_negotiate_features,  vtpci_negotiate_features),
> -     DEVMETHOD(virtio_bus_with_feature,        vtpci_with_feature),
> -     DEVMETHOD(virtio_bus_alloc_virtqueues,    vtpci_alloc_virtqueues),
> -     DEVMETHOD(virtio_bus_setup_intr,          vtpci_setup_intr),
> -     DEVMETHOD(virtio_bus_stop,                vtpci_stop),
> -     DEVMETHOD(virtio_bus_reinit,              vtpci_reinit),
> -     DEVMETHOD(virtio_bus_reinit_complete,     vtpci_reinit_complete),
> -     DEVMETHOD(virtio_bus_notify_vq,           vtpci_notify_virtqueue),
> -     DEVMETHOD(virtio_bus_read_device_config,  vtpci_read_dev_config),
> -     DEVMETHOD(virtio_bus_write_device_config, vtpci_write_dev_config),
> -
> -     DEVMETHOD_END
> -};
> -
> -static driver_t vtpci_driver = {
> -     "virtio_pci",
> -     vtpci_methods,
> -     sizeof(struct vtpci_softc)
> -};
> -
> -devclass_t vtpci_devclass;
> -
> -DRIVER_MODULE(virtio_pci, pci, vtpci_driver, vtpci_devclass, 0, 0);
> MODULE_VERSION(virtio_pci, 1);
> MODULE_DEPEND(virtio_pci, pci, 1, 1, 1);
> MODULE_DEPEND(virtio_pci, virtio, 1, 1, 1);
> 
> -static int
> -vtpci_probe(device_t dev)
> -{
> -     char desc[36];
> -     const char *name;
> +int vtpci_disable_msix = 0;
> +TUNABLE_INT("hw.virtio.pci.disable_msix", &vtpci_disable_msix);
> 
> -     if (pci_get_vendor(dev) != VIRTIO_PCI_VENDORID)
> -             return (ENXIO);
> +static uint8_t
> +vtpci_read_isr(struct vtpci_common *cn)
> +{
> +     return (VIRTIO_PCI_READ_ISR(cn->vtpci_dev));
> +}
> 
> -     if (pci_get_device(dev) < VIRTIO_PCI_DEVICEID_MIN ||
> -         pci_get_device(dev) > VIRTIO_PCI_DEVICEID_MAX)
> -             return (ENXIO);
> +static uint16_t
> +vtpci_get_vq_size(struct vtpci_common *cn, int idx)
> +{
> +     return (VIRTIO_PCI_GET_VQ_SIZE(cn->vtpci_dev, idx));
> +}
> 
> -     if (pci_get_revid(dev) != VIRTIO_PCI_ABI_VERSION)
> -             return (ENXIO);
> +static bus_size_t
> +vtpci_get_vq_notify_off(struct vtpci_common *cn, int idx)
> +{
> +     return (VIRTIO_PCI_GET_VQ_NOTIFY_OFF(cn->vtpci_dev, idx));
> +}
> 
> -     name = virtio_device_name(pci_get_subdevice(dev));
> -     if (name == NULL)
> -             name = "Unknown";
> +static void
> +vtpci_set_vq(struct vtpci_common *cn, struct virtqueue *vq)
> +{
> +     VIRTIO_PCI_SET_VQ(cn->vtpci_dev, vq);
> +}
> 
> -     snprintf(desc, sizeof(desc), "VirtIO PCI %s adapter", name);
> -     device_set_desc_copy(dev, desc);
> +static void
> +vtpci_disable_vq(struct vtpci_common *cn, int idx)
> +{
> +     VIRTIO_PCI_DISABLE_VQ(cn->vtpci_dev, idx);
> +}
> 
> -     return (BUS_PROBE_DEFAULT);
> +static int
> +vtpci_register_cfg_msix(struct vtpci_common *cn, struct vtpci_interrupt 
> *intr)
> +{
> +     return (VIRTIO_PCI_REGISTER_CFG_MSIX(cn->vtpci_dev, intr));
> }
> 
> static int
> -vtpci_attach(device_t dev)
> +vtpci_register_vq_msix(struct vtpci_common *cn, int idx,
> +    struct vtpci_interrupt *intr)
> {
> -     struct vtpci_softc *sc;
> -     device_t child;
> -     int rid;
> +     return (VIRTIO_PCI_REGISTER_VQ_MSIX(cn->vtpci_dev, idx, intr));
> +}
> 
> -     sc = device_get_softc(dev);
> -     sc->vtpci_dev = dev;
> +void
> +vtpci_init(struct vtpci_common *cn, device_t dev, bool modern)
> +{
> 
> -     pci_enable_busmaster(dev);
> +     cn->vtpci_dev = dev;
> 
> -     rid = PCIR_BAR(0);
> -     sc->vtpci_res = bus_alloc_resource_any(dev, SYS_RES_IOPORT, &rid,
> -         RF_ACTIVE);
> -     if (sc->vtpci_res == NULL) {
> -             device_printf(dev, "cannot map I/O space\n");
> -             return (ENXIO);
> -     }
> +     pci_enable_busmaster(dev);
> 
> +     if (modern)
> +             cn->vtpci_flags |= VTPCI_FLAG_MODERN;
>       if (pci_find_cap(dev, PCIY_MSI, NULL) != 0)
> -             sc->vtpci_flags |= VTPCI_FLAG_NO_MSI;
> -
> -     if (pci_find_cap(dev, PCIY_MSIX, NULL) == 0) {
> -             rid = PCIR_BAR(1);
> -             sc->vtpci_msix_res = bus_alloc_resource_any(dev,
> -                 SYS_RES_MEMORY, &rid, RF_ACTIVE);
> -     }
> -
> -     if (sc->vtpci_msix_res == NULL)
> -             sc->vtpci_flags |= VTPCI_FLAG_NO_MSIX;
> +             cn->vtpci_flags |= VTPCI_FLAG_NO_MSI;
> +     if (pci_find_cap(dev, PCIY_MSIX, NULL) != 0)
> +             cn->vtpci_flags |= VTPCI_FLAG_NO_MSIX;
> +}
> 
> -     vtpci_reset(sc);
> +int
> +vtpci_add_child(struct vtpci_common *cn)
> +{
> +     device_t dev, child;
> 
> -     /* Tell the host we've noticed this device. */
> -     vtpci_set_status(dev, VIRTIO_CONFIG_STATUS_ACK);
> +     dev = cn->vtpci_dev;
> 
> -     if ((child = device_add_child(dev, NULL, -1)) == NULL) {
> +     child = device_add_child(dev, NULL, -1);
> +     if (child == NULL) {
>               device_printf(dev, "cannot create child device\n");
> -             vtpci_set_status(dev, VIRTIO_CONFIG_STATUS_FAILED);
> -             vtpci_detach(dev);
>               return (ENOMEM);
>       }
> 
> -     sc->vtpci_child_dev = child;
> -     vtpci_probe_and_attach_child(sc);
> +     cn->vtpci_child_dev = child;
> 
>       return (0);
> }
> 
> -static int
> -vtpci_detach(device_t dev)
> +int
> +vtpci_delete_child(struct vtpci_common *cn)
> {
> -     struct vtpci_softc *sc;
> -     device_t child;
> +     device_t dev, child;
>       int error;
> 
> -     sc = device_get_softc(dev);
> +     dev = cn->vtpci_dev;
> 
> -     if ((child = sc->vtpci_child_dev) != NULL) {
> +     child = cn->vtpci_child_dev;
> +     if (child != NULL) {
>               error = device_delete_child(dev, child);
>               if (error)
>                       return (error);
> -             sc->vtpci_child_dev = NULL;
> -     }
> -
> -     vtpci_reset(sc);
> -
> -     if (sc->vtpci_msix_res != NULL) {
> -             bus_release_resource(dev, SYS_RES_MEMORY, PCIR_BAR(1),
> -                 sc->vtpci_msix_res);
> -             sc->vtpci_msix_res = NULL;
> -     }
> -
> -     if (sc->vtpci_res != NULL) {
> -             bus_release_resource(dev, SYS_RES_IOPORT, PCIR_BAR(0),
> -                 sc->vtpci_res);
> -             sc->vtpci_res = NULL;
> +             cn->vtpci_child_dev = NULL;
>       }
> 
>       return (0);
> }
> 
> -static int
> -vtpci_suspend(device_t dev)
> +void
> +vtpci_child_detached(struct vtpci_common *cn)
> {
> 
> -     return (bus_generic_suspend(dev));
> -}
> -
> -static int
> -vtpci_resume(device_t dev)
> -{
> +     vtpci_release_child_resources(cn);
> 
> -     return (bus_generic_resume(dev));
> +     cn->vtpci_child_feat_desc = NULL;
> +     cn->vtpci_features = 0;
> }
> 
> -static int
> -vtpci_shutdown(device_t dev)
> +int
> +vtpci_reinit(struct vtpci_common *cn)
> {
> +     int idx, error;
> 
> -     (void) bus_generic_shutdown(dev);
> -     /* Forcibly stop the host device. */
> -     vtpci_stop(dev);
> +     for (idx = 0; idx < cn->vtpci_nvqs; idx++) {
> +             error = vtpci_reinit_virtqueue(cn, idx);
> +             if (error)
> +                     return (error);
> +     }
> +
> +     if (vtpci_is_msix_enabled(cn)) {
> +             error = vtpci_set_host_msix_vectors(cn);
> +             if (error)
> +                     return (error);
> +     }
> 
>       return (0);
> }
> 
> static void
> -vtpci_driver_added(device_t dev, driver_t *driver)
> +vtpci_describe_features(struct vtpci_common *cn, const char *msg,
> +    uint64_t features)
> {
> -     struct vtpci_softc *sc;
> +     device_t dev, child;
> +
> +     dev = cn->vtpci_dev;
> +     child = cn->vtpci_child_dev;
> 
> -     sc = device_get_softc(dev);
> +     if (device_is_attached(child) || bootverbose == 0)
> +             return;
> 
> -     vtpci_probe_and_attach_child(sc);
> +     virtio_describe(dev, msg, features, cn->vtpci_child_feat_desc);
> }
> 
> -static void
> -vtpci_child_detached(device_t dev, device_t child)
> +uint64_t
> +vtpci_negotiate_features(struct vtpci_common *cn,
> +    uint64_t child_features, uint64_t host_features)
> {
> -     struct vtpci_softc *sc;
> +     uint64_t features;
> 
> -     sc = device_get_softc(dev);
> +     vtpci_describe_features(cn, "host", host_features);
> 
> -     vtpci_reset(sc);
> -     vtpci_release_child_resources(sc);
> +     /*
> +      * Limit negotiated features to what the driver, virtqueue, and
> +      * host all support.
> +      */
> +     features = host_features & child_features;
> +     features = virtio_filter_transport_features(features);
> +     vtpci_describe_features(cn, "negotiated", features);
> +
> +     cn->vtpci_features = features;
> +
> +     return (features);
> }
> 
> -static int
> -vtpci_read_ivar(device_t dev, device_t child, int index, uintptr_t *result)
> +int
> +vtpci_with_feature(struct vtpci_common *cn, uint64_t feature)
> {
> -     struct vtpci_softc *sc;
> +     return ((cn->vtpci_features & feature) != 0);
> +}
> 
> -     sc = device_get_softc(dev);
> +int
> +vtpci_read_ivar(struct vtpci_common *cn, int index, uintptr_t *result)
> +{
> +     device_t dev;
> +     int error;
> 
> -     if (sc->vtpci_child_dev != child)
> -             return (ENOENT);
> +     dev = cn->vtpci_dev;
> +     error = 0;
> 
>       switch (index) {
> -     case VIRTIO_IVAR_DEVTYPE:
>       case VIRTIO_IVAR_SUBDEVICE:
>               *result = pci_get_subdevice(dev);
>               break;
> @@ -425,100 +289,74 @@ vtpci_read_ivar(device_t dev, device_t child, int 
> index, uintptr_t *result)
>       case VIRTIO_IVAR_SUBVENDOR:
>               *result = pci_get_subvendor(dev);
>               break;
> +     case VIRTIO_IVAR_MODERN:
> +             *result = vtpci_is_modern(cn);
> +             break;
>       default:
> -             return (ENOENT);
> +             error = ENOENT;
>       }
> 
> -     return (0);
> +     return (error);
> }
> 
> -static int
> -vtpci_write_ivar(device_t dev, device_t child, int index, uintptr_t value)
> +int
> +vtpci_write_ivar(struct vtpci_common *cn, int index, uintptr_t value)
> {
> -     struct vtpci_softc *sc;
> -
> -     sc = device_get_softc(dev);
> +     int error;
> 
> -     if (sc->vtpci_child_dev != child)
> -             return (ENOENT);
> +     error = 0;
> 
>       switch (index) {
>       case VIRTIO_IVAR_FEATURE_DESC:
> -             sc->vtpci_child_feat_desc = (void *) value;
> +             cn->vtpci_child_feat_desc = (void *) value;
>               break;
>       default:
> -             return (ENOENT);
> +             error = ENOENT;
>       }
> 
> -     return (0);
> +     return (error);
> }
> 
> -static uint64_t
> -vtpci_negotiate_features(device_t dev, uint64_t child_features)
> +int
> +vtpci_alloc_virtqueues(struct vtpci_common *cn, int flags, int nvqs,
> +    struct vq_alloc_info *vq_info)
> {
> -     struct vtpci_softc *sc;
> -     uint64_t host_features, features;
> -
> -     sc = device_get_softc(dev);
> +     device_t dev;
> +     int idx, align, error;
> 
> -     host_features = vtpci_read_header_4(sc, VIRTIO_PCI_HOST_FEATURES);
> -     vtpci_describe_features(sc, "host", host_features);
> +     dev = cn->vtpci_dev;
> 
>       /*
> -      * Limit negotiated features to what the driver, virtqueue, and
> -      * host all support.
> +      * This is VIRTIO_PCI_VRING_ALIGN from legacy VirtIO. In modern VirtIO,
> +      * the tables do not have to be allocated contiguously, but we do so
> +      * anyways.
>        */
> -     features = host_features & child_features;
> -     features = virtqueue_filter_features(features);
> -     sc->vtpci_features = features;
> -
> -     vtpci_describe_features(sc, "negotiated", features);
> -     vtpci_write_header_4(sc, VIRTIO_PCI_GUEST_FEATURES, features);
> -
> -     return (features);
> -}
> -
> -static int
> -vtpci_with_feature(device_t dev, uint64_t feature)
> -{
> -     struct vtpci_softc *sc;
> +     align = 4096;
> 
> -     sc = device_get_softc(dev);
> -
> -     return ((sc->vtpci_features & feature) != 0);
> -}
> -
> -static int
> -vtpci_alloc_virtqueues(device_t dev, int flags, int nvqs,
> -    struct vq_alloc_info *vq_info)
> -{
> -     struct vtpci_softc *sc;
> -     struct virtqueue *vq;
> -     struct vtpci_virtqueue *vqx;
> -     struct vq_alloc_info *info;
> -     int idx, error;
> -     uint16_t size;
> -
> -     sc = device_get_softc(dev);
> -
> -     if (sc->vtpci_nvqs != 0)
> +     if (cn->vtpci_nvqs != 0)
>               return (EALREADY);
>       if (nvqs <= 0)
>               return (EINVAL);
> 
> -     sc->vtpci_vqs = malloc(nvqs * sizeof(struct vtpci_virtqueue),
> +     cn->vtpci_vqs = malloc(nvqs * sizeof(struct vtpci_virtqueue),
>           M_DEVBUF, M_NOWAIT | M_ZERO);
> -     if (sc->vtpci_vqs == NULL)
> +     if (cn->vtpci_vqs == NULL)
>               return (ENOMEM);
> 
>       for (idx = 0; idx < nvqs; idx++) {
> -             vqx = &sc->vtpci_vqs[idx];
> +             struct vtpci_virtqueue *vqx;
> +             struct vq_alloc_info *info;
> +             struct virtqueue *vq;
> +             bus_size_t notify_offset;
> +             uint16_t size;
> +
> +             vqx = &cn->vtpci_vqs[idx];
>               info = &vq_info[idx];
> 
> -             vtpci_select_virtqueue(sc, idx);
> -             size = vtpci_read_header_2(sc, VIRTIO_PCI_QUEUE_NUM);
> +             size = vtpci_get_vq_size(cn, idx);
> +             notify_offset = vtpci_get_vq_notify_off(cn, idx);
> 
> -             error = virtqueue_alloc(dev, idx, size, VIRTIO_PCI_VRING_ALIGN,
> +             error = virtqueue_alloc(dev, idx, size, notify_offset, align,
>                   ~(vm_paddr_t)0, info, &vq);
>               if (error) {
>                       device_printf(dev,
> @@ -526,270 +364,27 @@ vtpci_alloc_virtqueues(device_t dev, int flags, int 
> nvqs,
>                       break;
>               }
> 
> -             vtpci_write_header_4(sc, VIRTIO_PCI_QUEUE_PFN,
> -                 virtqueue_paddr(vq) >> VIRTIO_PCI_QUEUE_ADDR_SHIFT);
> +             vtpci_set_vq(cn, vq);
> 
>               vqx->vtv_vq = *info->vqai_vq = vq;
>               vqx->vtv_no_intr = info->vqai_intr == NULL;
> 
> -             sc->vtpci_nvqs++;
> +             cn->vtpci_nvqs++;
>       }
> 
>       if (error)
> -             vtpci_free_virtqueues(sc);
> +             vtpci_free_virtqueues(cn);
> 
>       return (error);
> }
> 
> static int
> -vtpci_setup_intr(device_t dev, enum intr_type type)
> -{
> -     struct vtpci_softc *sc;
> -     int attempt, error;
> -
> -     sc = device_get_softc(dev);
> -
> -     for (attempt = 0; attempt < 5; attempt++) {
> -             /*
> -              * Start with the most desirable interrupt configuration and
> -              * fallback towards less desirable ones.
> -              */
> -             switch (attempt) {
> -             case 0:
> -                     error = vtpci_alloc_intr_msix_pervq(sc);
> -                     break;
> -             case 1:
> -                     error = vtpci_alloc_intr_msix_shared(sc);
> -                     break;
> -             case 2:
> -                     error = vtpci_alloc_intr_msi(sc);
> -                     break;
> -             case 3:
> -                     error = vtpci_alloc_intr_legacy(sc);
> -                     break;
> -             default:
> -                     device_printf(dev,
> -                         "exhausted all interrupt allocation attempts\n");
> -                     return (ENXIO);
> -             }
> -
> -             if (error == 0 && vtpci_setup_interrupts(sc, type) == 0)
> -                     break;
> -
> -             vtpci_cleanup_setup_intr_attempt(sc);
> -     }
> -
> -     if (bootverbose) {
> -             if (sc->vtpci_flags & VTPCI_FLAG_LEGACY)
> -                     device_printf(dev, "using legacy interrupt\n");
> -             else if (sc->vtpci_flags & VTPCI_FLAG_MSI)
> -                     device_printf(dev, "using MSI interrupt\n");
> -             else if (sc->vtpci_flags & VTPCI_FLAG_SHARED_MSIX)
> -                     device_printf(dev, "using shared MSIX interrupts\n");
> -             else
> -                     device_printf(dev, "using per VQ MSIX interrupts\n");
> -     }
> -
> -     return (0);
> -}
> -
> -static void
> -vtpci_stop(device_t dev)
> -{
> -
> -     vtpci_reset(device_get_softc(dev));
> -}
> -
> -static int
> -vtpci_reinit(device_t dev, uint64_t features)
> -{
> -     struct vtpci_softc *sc;
> -     int idx, error;
> -
> -     sc = device_get_softc(dev);
> -
> -     /*
> -      * Redrive the device initialization. This is a bit of an abuse of
> -      * the specification, but VirtualBox, QEMU/KVM, and BHyVe seem to
> -      * play nice.
> -      *
> -      * We do not allow the host device to change from what was originally
> -      * negotiated beyond what the guest driver changed. MSIX state should
> -      * not change, number of virtqueues and their size remain the same, etc.
> -      * This will need to be rethought when we want to support migration.
> -      */
> -
> -     if (vtpci_get_status(dev) != VIRTIO_CONFIG_STATUS_RESET)
> -             vtpci_stop(dev);
> -
> -     /*
> -      * Quickly drive the status through ACK and DRIVER. The device
> -      * does not become usable again until vtpci_reinit_complete().
> -      */
> -     vtpci_set_status(dev, VIRTIO_CONFIG_STATUS_ACK);
> -     vtpci_set_status(dev, VIRTIO_CONFIG_STATUS_DRIVER);
> -
> -     vtpci_negotiate_features(dev, features);
> -
> -     for (idx = 0; idx < sc->vtpci_nvqs; idx++) {
> -             error = vtpci_reinit_virtqueue(sc, idx);
> -             if (error)
> -                     return (error);
> -     }
> -
> -     if (sc->vtpci_flags & VTPCI_FLAG_MSIX) {
> -             error = vtpci_set_host_msix_vectors(sc);
> -             if (error)
> -                     return (error);
> -     }
> -
> -     return (0);
> -}
> -
> -static void
> -vtpci_reinit_complete(device_t dev)
> -{
> -
> -     vtpci_set_status(dev, VIRTIO_CONFIG_STATUS_DRIVER_OK);
> -}
> -
> -static void
> -vtpci_notify_virtqueue(device_t dev, uint16_t queue)
> -{
> -     struct vtpci_softc *sc;
> -
> -     sc = device_get_softc(dev);
> -
> -     vtpci_write_header_2(sc, VIRTIO_PCI_QUEUE_NOTIFY, queue);
> -}
> -
> -static uint8_t
> -vtpci_get_status(device_t dev)
> -{
> -     struct vtpci_softc *sc;
> -
> -     sc = device_get_softc(dev);
> -
> -     return (vtpci_read_config_1(sc, VIRTIO_PCI_STATUS));
> -}
> -
> -static void
> -vtpci_set_status(device_t dev, uint8_t status)
> -{
> -     struct vtpci_softc *sc;
> -
> -     sc = device_get_softc(dev);
> -
> -     if (status != VIRTIO_CONFIG_STATUS_RESET)
> -             status |= vtpci_get_status(dev);
> -
> -     vtpci_write_config_1(sc, VIRTIO_PCI_STATUS, status);
> -}
> -
> -static void
> -vtpci_read_dev_config(device_t dev, bus_size_t offset,
> *** 4018 LINES SKIPPED ***

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