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virtio-pci: reduce modern_mem_bar size

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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: Marcel Apfelbaum <marcel@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Marcel Apfelbaum 2016-09-07 18:02:25 +03:00 • committed by Michael S. Tsirkin
parent 14c985cffa
commit d9997d89a4
3 changed files with 25 additions and 8 deletions
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5
hw/virtio/virtio-pci.h
View file

@ -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;