Commit d9997d89 authored by Marcel Apfelbaum's avatar Marcel Apfelbaum Committed by Michael S. Tsirkin
Browse files

virtio-pci: reduce modern_mem_bar size 



Currently each VQ Notification Virtio Capability is allocated
on a different page. The idea is to enable split drivers within
guests, however there are no known plans to do that.
The allocation will result in a 8MB BAR, more than various
guest firmwares pre-allocates for PCI Bridges hotplug process.

Reserve 4 bytes per VQ by default and add a new parameter
"page-per-vq" to be used with split drivers.

Signed-off-by: default avatarMarcel Apfelbaum <marcel@redhat.com>
Reviewed-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent 14c985cf

hw/virtio/virtio-pci.c

+15 −7
Original line number Diff line number Diff line
@@ -294,6 +294,12 @@ static void virtio_pci_ioeventfd_set_disabled(DeviceState *d, bool disabled) 


#define QEMU_VIRTIO_PCI_QUEUE_MEM_MULT 0x1000



static inline int virtio_pci_queue_mem_mult(struct VirtIOPCIProxy *proxy)

{

    return (proxy->flags & VIRTIO_PCI_FLAG_PAGE_PER_VQ) ?

        QEMU_VIRTIO_PCI_QUEUE_MEM_MULT : 4;

}



static int virtio_pci_ioeventfd_assign(DeviceState *d, EventNotifier *notifier,

                                       int n, bool assign)

{
@@ -307,7 +313,7 @@ static int virtio_pci_ioeventfd_assign(DeviceState *d, EventNotifier *notifier, 
    MemoryRegion *modern_mr = &proxy->notify.mr;

    MemoryRegion *modern_notify_mr = &proxy->notify_pio.mr;

    MemoryRegion *legacy_mr = &proxy->bar;

    hwaddr modern_addr = QEMU_VIRTIO_PCI_QUEUE_MEM_MULT *

    hwaddr modern_addr = virtio_pci_queue_mem_mult(proxy) *

                         virtio_get_queue_index(vq);

    hwaddr legacy_addr = VIRTIO_PCI_QUEUE_NOTIFY;
@@ -1370,7 +1376,8 @@ static void virtio_pci_notify_write(void *opaque, hwaddr addr, 
                                    uint64_t val, unsigned size)

{

    VirtIODevice *vdev = opaque;

    unsigned queue = addr / QEMU_VIRTIO_PCI_QUEUE_MEM_MULT;

    VirtIOPCIProxy *proxy = VIRTIO_PCI(DEVICE(vdev)->parent_bus->parent);

    unsigned queue = addr / virtio_pci_queue_mem_mult(proxy);



    if (queue < VIRTIO_QUEUE_MAX) {

        virtio_queue_notify(vdev, queue);
@@ -1609,7 +1616,7 @@ static void virtio_pci_device_plugged(DeviceState *d, Error **errp) 
        struct virtio_pci_notify_cap notify = {

            .cap.cap_len = sizeof notify,

            .notify_off_multiplier =

                cpu_to_le32(QEMU_VIRTIO_PCI_QUEUE_MEM_MULT),

                cpu_to_le32(virtio_pci_queue_mem_mult(proxy)),

        };

        struct virtio_pci_cfg_cap cfg = {

            .cap.cap_len = sizeof cfg,
@@ -1744,8 +1751,7 @@ static void virtio_pci_realize(PCIDevice *pci_dev, Error **errp) 
    proxy->device.type = VIRTIO_PCI_CAP_DEVICE_CFG;



    proxy->notify.offset = 0x3000;

    proxy->notify.size =

        QEMU_VIRTIO_PCI_QUEUE_MEM_MULT * VIRTIO_QUEUE_MAX;

    proxy->notify.size = virtio_pci_queue_mem_mult(proxy) * VIRTIO_QUEUE_MAX;

    proxy->notify.type = VIRTIO_PCI_CAP_NOTIFY_CFG;



    proxy->notify_pio.offset = 0x0;
@@ -1754,8 +1760,8 @@ static void virtio_pci_realize(PCIDevice *pci_dev, Error **errp) 


    /* subclasses can enforce modern, so do this unconditionally */

    memory_region_init(&proxy->modern_bar, OBJECT(proxy), "virtio-pci",

                       2 * QEMU_VIRTIO_PCI_QUEUE_MEM_MULT *

                       VIRTIO_QUEUE_MAX);

                       /* PCI BAR regions must be powers of 2 */

                       pow2ceil(proxy->notify.offset + proxy->notify.size));



    memory_region_init_alias(&proxy->modern_cfg,

                             OBJECT(proxy),
@@ -1833,6 +1839,8 @@ static Property virtio_pci_properties[] = { 
                    VIRTIO_PCI_FLAG_MODERN_PIO_NOTIFY_BIT, false),

    DEFINE_PROP_BIT("x-disable-pcie", VirtIOPCIProxy, flags,

                    VIRTIO_PCI_FLAG_DISABLE_PCIE_BIT, false),

    DEFINE_PROP_BIT("page-per-vq", VirtIOPCIProxy, flags,

                    VIRTIO_PCI_FLAG_PAGE_PER_VQ_BIT, false),

    DEFINE_PROP_END_OF_LIST(),

};

hw/virtio/virtio-pci.h

+5 −0
Original line number Diff line number Diff line
@@ -64,6 +64,7 @@ enum { 
    VIRTIO_PCI_FLAG_MIGRATE_EXTRA_BIT,

    VIRTIO_PCI_FLAG_MODERN_PIO_NOTIFY_BIT,

    VIRTIO_PCI_FLAG_DISABLE_PCIE_BIT,

    VIRTIO_PCI_FLAG_PAGE_PER_VQ_BIT,

};



/* Need to activate work-arounds for buggy guests at vmstate load. */
@@ -84,6 +85,10 @@ enum { 
#define VIRTIO_PCI_FLAG_MODERN_PIO_NOTIFY \

    (1 << VIRTIO_PCI_FLAG_MODERN_PIO_NOTIFY_BIT)



/* page per vq flag to be used by split drivers within guests */

#define VIRTIO_PCI_FLAG_PAGE_PER_VQ \

    (1 << VIRTIO_PCI_FLAG_PAGE_PER_VQ_BIT)



typedef struct {

    MSIMessage msg;

    int virq;

include/hw/compat.h

+5 −1
Original line number Diff line number Diff line
@@ -2,7 +2,11 @@ 
#define HW_COMPAT_H



#define HW_COMPAT_2_7 \

        /* empty */

    {\

        .driver   = "virtio-pci",\

        .property = "page-per-vq",\

        .value    = "on",\

    },



#define HW_COMPAT_2_6 \

    {\