From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:47650) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S9i7O-00034l-Ou for qemu-devel@nongnu.org; Mon, 19 Mar 2012 15:19:49 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1S9i7I-0000AW-8v for qemu-devel@nongnu.org; Mon, 19 Mar 2012 15:19:46 -0400 Received: from mail-pz0-f45.google.com ([209.85.210.45]:33002) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S9i7H-0000AP-VA for qemu-devel@nongnu.org; Mon, 19 Mar 2012 15:19:40 -0400 Received: by dadp14 with SMTP id p14so11466102dad.4 for ; Mon, 19 Mar 2012 12:19:38 -0700 (PDT) Message-ID: <4F6786C5.3080902@codemonkey.ws> Date: Mon, 19 Mar 2012 14:19:33 -0500 From: Anthony Liguori MIME-Version: 1.0 References: <20120319155650.GA6430@redhat.com> In-Reply-To: <20120319155650.GA6430@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH RFC] virtio-pci: add MMIO property List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: Anthony Liguori , kvm@vger.kernel.org, Alexey Kardashevskiy , rusty@rustcorp.com.au, qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org, avi@redhat.com 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 > > 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;