Currently virtio-pci is specified so that configuration of the device is
done through a PCI IO space (via BAR 0 of the virtual PCI device).
However, Linux guests happen to use ioread/iowrite/iomap primitives
for access, and these work uniformly across memory/io BARs.
While PCI IO accesses are faster than MMIO on x86 kvm,
MMIO might be helpful on other systems which don't
implement PIO or where PIO is slower than MMIO.
Add a property to make it possible to tweak the BAR type.
Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
This is harmless by default but causes segfaults in memory.c
when enabled. Thus an RFC until I figure out what's wrong.
---
hw/virtio-pci.c | 16 ++++++++++++++--
hw/virtio-pci.h | 4 ++++
2 files changed, 18 insertions(+), 2 deletions(-)
diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
index 28498ec..6f338d2 100644
--- a/hw/virtio-pci.c
+++ b/hw/virtio-pci.c
@@ -655,6 +655,7 @@ void virtio_init_pci(VirtIOPCIProxy *proxy, VirtIODevice
*vdev)
{
uint8_t *config;
uint32_t size;
+ uint8_t bar0_type;
proxy->vdev = vdev;
@@ -684,8 +685,14 @@ void virtio_init_pci(VirtIOPCIProxy *proxy, VirtIODevice
*vdev)
memory_region_init_io(&proxy->bar, &virtio_pci_config_ops,
proxy,
"virtio-pci", size);
- pci_register_bar(&proxy->pci_dev, 0, PCI_BASE_ADDRESS_SPACE_IO,
- &proxy->bar);
+
+ if (proxy->flags & VIRTIO_PCI_FLAG_USE_MMIO) {
+ bar0_type = PCI_BASE_ADDRESS_SPACE_MEMORY;
+ } else {
+ bar0_type = PCI_BASE_ADDRESS_SPACE_IO;
+ }
+
+ pci_register_bar(&proxy->pci_dev, 0, bar0_type, &proxy->bar);
if (!kvm_has_many_ioeventfds()) {
proxy->flags &= ~VIRTIO_PCI_FLAG_USE_IOEVENTFD;
@@ -823,6 +830,7 @@ static Property virtio_blk_properties[] = {
DEFINE_PROP_BIT("ioeventfd", VirtIOPCIProxy, flags,
VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT, true),
DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors, 2),
DEFINE_VIRTIO_BLK_FEATURES(VirtIOPCIProxy, host_features),
+ DEFINE_PROP_BIT("mmio", VirtIOPCIProxy, flags,
VIRTIO_PCI_FLAG_USE_MMIO_BIT, false),
DEFINE_PROP_END_OF_LIST(),
};
@@ -856,6 +864,7 @@ static Property virtio_net_properties[] = {
DEFINE_PROP_UINT32("x-txtimer", VirtIOPCIProxy, net.txtimer,
TX_TIMER_INTERVAL),
DEFINE_PROP_INT32("x-txburst", VirtIOPCIProxy, net.txburst,
TX_BURST),
DEFINE_PROP_STRING("tx", VirtIOPCIProxy, net.tx),
+ DEFINE_PROP_BIT("mmio", VirtIOPCIProxy, flags,
VIRTIO_PCI_FLAG_USE_MMIO_BIT, false),
DEFINE_PROP_END_OF_LIST(),
};
@@ -888,6 +897,7 @@ static Property virtio_serial_properties[] = {
DEFINE_PROP_HEX32("class", VirtIOPCIProxy, class_code, 0),
DEFINE_VIRTIO_COMMON_FEATURES(VirtIOPCIProxy, host_features),
DEFINE_PROP_UINT32("max_ports", VirtIOPCIProxy,
serial.max_virtserial_ports, 31),
+ DEFINE_PROP_BIT("mmio", VirtIOPCIProxy, flags,
VIRTIO_PCI_FLAG_USE_MMIO_BIT, false),
DEFINE_PROP_END_OF_LIST(),
};
@@ -915,6 +925,7 @@ static TypeInfo virtio_serial_info = {
static Property virtio_balloon_properties[] = {
DEFINE_VIRTIO_COMMON_FEATURES(VirtIOPCIProxy, host_features),
+ DEFINE_PROP_BIT("mmio", VirtIOPCIProxy, flags,
VIRTIO_PCI_FLAG_USE_MMIO_BIT, false),
DEFINE_PROP_END_OF_LIST(),
};
@@ -969,6 +980,7 @@ static int virtio_scsi_exit_pci(PCIDevice *pci_dev)
static Property virtio_scsi_properties[] = {
DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors, 2),
DEFINE_VIRTIO_SCSI_PROPERTIES(VirtIOPCIProxy, host_features, scsi),
+ DEFINE_PROP_BIT("mmio", VirtIOPCIProxy, flags,
VIRTIO_PCI_FLAG_USE_MMIO_BIT, false),
DEFINE_PROP_END_OF_LIST(),
};
diff --git a/hw/virtio-pci.h b/hw/virtio-pci.h
index e560428..e6a8861 100644
--- a/hw/virtio-pci.h
+++ b/hw/virtio-pci.h
@@ -24,6 +24,10 @@
#define VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT 1
#define VIRTIO_PCI_FLAG_USE_IOEVENTFD (1 <<
VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT)
+/* Some guests don't support port IO. Use MMIO instead. */
+#define VIRTIO_PCI_FLAG_USE_MMIO_BIT 2
+#define VIRTIO_PCI_FLAG_USE_MMIO (1 << VIRTIO_PCI_FLAG_USE_MMIO_BIT)
+
typedef struct {
PCIDevice pci_dev;
VirtIODevice *vdev;
--
1.7.9.111.gf3fb0
On 03/19/2012 05:56 PM, Michael S. Tsirkin wrote:> Currently virtio-pci is specified so that configuration of the device is > done through a PCI IO space (via BAR 0 of the virtual PCI device). > However, Linux guests happen to use ioread/iowrite/iomap primitives > for access, and these work uniformly across memory/io BARs. > > While PCI IO accesses are faster than MMIO on x86 kvm, > MMIO might be helpful on other systems which don't > implement PIO or where PIO is slower than MMIO. > > Add a property to make it possible to tweak the BAR type. > > Signed-off-by: Michael S. Tsirkin <mst at redhat.com> > > This is harmless by default but causes segfaults in memory.c > when enabled. Thus an RFC until I figure out what's wrong. >Should be done via an extra BAR (with the same layout, perhaps extended) so compatibility is preserved. -- error compiling committee.c: too many arguments to function
Anthony Liguori
2012-Mar-19 19:19 UTC
[Qemu-devel] [PATCH RFC] virtio-pci: add MMIO property
On 03/19/2012 10:56 AM, Michael S. Tsirkin wrote:> Currently virtio-pci is specified so that configuration of the device is > done through a PCI IO space (via BAR 0 of the virtual PCI device). > However, Linux guests happen to use ioread/iowrite/iomap primitives > for access, and these work uniformly across memory/io BARs. > > While PCI IO accesses are faster than MMIO on x86 kvm, > MMIO might be helpful on other systems which don't > implement PIO or where PIO is slower than MMIO. > > Add a property to make it possible to tweak the BAR type. > > Signed-off-by: Michael S. Tsirkin<mst at redhat.com> > > This is harmless by default but causes segfaults in memory.c > when enabled. Thus an RFC until I figure out what's wrong.Doesn't this violate the virtio-pci spec? Making the same vendor/device ID have different semantics depending on a magic flag in QEMU seems like a pretty bad idea to me. Regards, Anthony Liguori> > --- > hw/virtio-pci.c | 16 ++++++++++++++-- > hw/virtio-pci.h | 4 ++++ > 2 files changed, 18 insertions(+), 2 deletions(-) > > diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c > index 28498ec..6f338d2 100644 > --- a/hw/virtio-pci.c > +++ b/hw/virtio-pci.c > @@ -655,6 +655,7 @@ void virtio_init_pci(VirtIOPCIProxy *proxy, VirtIODevice *vdev) > { > uint8_t *config; > uint32_t size; > + uint8_t bar0_type; > > proxy->vdev = vdev; > > @@ -684,8 +685,14 @@ void virtio_init_pci(VirtIOPCIProxy *proxy, VirtIODevice *vdev) > > memory_region_init_io(&proxy->bar,&virtio_pci_config_ops, proxy, > "virtio-pci", size); > - pci_register_bar(&proxy->pci_dev, 0, PCI_BASE_ADDRESS_SPACE_IO, > -&proxy->bar); > + > + if (proxy->flags& VIRTIO_PCI_FLAG_USE_MMIO) { > + bar0_type = PCI_BASE_ADDRESS_SPACE_MEMORY; > + } else { > + bar0_type = PCI_BASE_ADDRESS_SPACE_IO; > + } > + > + pci_register_bar(&proxy->pci_dev, 0, bar0_type,&proxy->bar); > > if (!kvm_has_many_ioeventfds()) { > proxy->flags&= ~VIRTIO_PCI_FLAG_USE_IOEVENTFD; > @@ -823,6 +830,7 @@ static Property virtio_blk_properties[] = { > DEFINE_PROP_BIT("ioeventfd", VirtIOPCIProxy, flags, VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT, true), > DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors, 2), > DEFINE_VIRTIO_BLK_FEATURES(VirtIOPCIProxy, host_features), > + DEFINE_PROP_BIT("mmio", VirtIOPCIProxy, flags, VIRTIO_PCI_FLAG_USE_MMIO_BIT, false), > DEFINE_PROP_END_OF_LIST(), > }; > > @@ -856,6 +864,7 @@ static Property virtio_net_properties[] = { > DEFINE_PROP_UINT32("x-txtimer", VirtIOPCIProxy, net.txtimer, TX_TIMER_INTERVAL), > DEFINE_PROP_INT32("x-txburst", VirtIOPCIProxy, net.txburst, TX_BURST), > DEFINE_PROP_STRING("tx", VirtIOPCIProxy, net.tx), > + DEFINE_PROP_BIT("mmio", VirtIOPCIProxy, flags, VIRTIO_PCI_FLAG_USE_MMIO_BIT, false), > DEFINE_PROP_END_OF_LIST(), > }; > > @@ -888,6 +897,7 @@ static Property virtio_serial_properties[] = { > DEFINE_PROP_HEX32("class", VirtIOPCIProxy, class_code, 0), > DEFINE_VIRTIO_COMMON_FEATURES(VirtIOPCIProxy, host_features), > DEFINE_PROP_UINT32("max_ports", VirtIOPCIProxy, serial.max_virtserial_ports, 31), > + DEFINE_PROP_BIT("mmio", VirtIOPCIProxy, flags, VIRTIO_PCI_FLAG_USE_MMIO_BIT, false), > DEFINE_PROP_END_OF_LIST(), > }; > > @@ -915,6 +925,7 @@ static TypeInfo virtio_serial_info = { > > static Property virtio_balloon_properties[] = { > DEFINE_VIRTIO_COMMON_FEATURES(VirtIOPCIProxy, host_features), > + DEFINE_PROP_BIT("mmio", VirtIOPCIProxy, flags, VIRTIO_PCI_FLAG_USE_MMIO_BIT, false), > DEFINE_PROP_END_OF_LIST(), > }; > > @@ -969,6 +980,7 @@ static int virtio_scsi_exit_pci(PCIDevice *pci_dev) > static Property virtio_scsi_properties[] = { > DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors, 2), > DEFINE_VIRTIO_SCSI_PROPERTIES(VirtIOPCIProxy, host_features, scsi), > + DEFINE_PROP_BIT("mmio", VirtIOPCIProxy, flags, VIRTIO_PCI_FLAG_USE_MMIO_BIT, false), > DEFINE_PROP_END_OF_LIST(), > }; > > diff --git a/hw/virtio-pci.h b/hw/virtio-pci.h > index e560428..e6a8861 100644 > --- a/hw/virtio-pci.h > +++ b/hw/virtio-pci.h > @@ -24,6 +24,10 @@ > #define VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT 1 > #define VIRTIO_PCI_FLAG_USE_IOEVENTFD (1<< VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT) > > +/* Some guests don't support port IO. Use MMIO instead. */ > +#define VIRTIO_PCI_FLAG_USE_MMIO_BIT 2 > +#define VIRTIO_PCI_FLAG_USE_MMIO (1<< VIRTIO_PCI_FLAG_USE_MMIO_BIT) > + > typedef struct { > PCIDevice pci_dev; > VirtIODevice *vdev;