From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:36301) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S9kpX-0007wO-BS for qemu-devel@nongnu.org; Mon, 19 Mar 2012 18:13:33 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1S9kpD-0008Dy-0L for qemu-devel@nongnu.org; Mon, 19 Mar 2012 18:13:30 -0400 Received: from mail-yw0-f45.google.com ([209.85.213.45]:40451) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S9kpC-0008Dh-RC for qemu-devel@nongnu.org; Mon, 19 Mar 2012 18:13:10 -0400 Received: by yhoo21 with SMTP id o21so6908628yho.4 for ; Mon, 19 Mar 2012 15:13:09 -0700 (PDT) Message-ID: <4F67AF72.8080905@codemonkey.ws> Date: Mon, 19 Mar 2012 17:13:06 -0500 From: Anthony Liguori MIME-Version: 1.0 References: <20120319155650.GA6430@redhat.com> <4F6786C5.3080902@codemonkey.ws> <20120319204952.GA9747@redhat.com> <4F67A021.6040601@us.ibm.com> <20120319212916.GC9747@redhat.com> In-Reply-To: <20120319212916.GC9747@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 04:29 PM, Michael S. Tsirkin wrote: > On Mon, Mar 19, 2012 at 04:07:45PM -0500, Anthony Liguori wrote: >> On 03/19/2012 03:49 PM, Michael S. Tsirkin wrote: >>> On Mon, Mar 19, 2012 at 02:19:33PM -0500, Anthony Liguori wrote: >>>> 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? >>>> >>> >>> The point is to change the BAR type depending on the architecture. >>> IO is fastest on x86 but maybe not on other architectures. >> >> Are we going to document that the BAR is X on architecture Y in the spec? >> >> I think the better way to do this is to use a separate device id >> range for MMIO virtio-pci. You can make the same driver hand both >> ranges and that way the device is presented consistently to the >> guest regardless of what the architecture is. > > Maybe just make this a hidden option like x-miio? x-violate-the-virtio-spec-to-trick-old-linux-drivers-into-working-on-power? Really, aren't we just being too clever here? From a practical perspective, I doubt anyone is ever going to support a driver that has *never* been tested on the platform just because it was accidentally compiled and happens to be there. If we just do use a device PCI device id range for this, it's a 1-line patch that can be provided via an update to existing guests. Regards, Anthony Liguori > This will ensure people dont turn it on by mistake on e.g. x86. > >>>> 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 >>> >>> We do this with MSI-X so why not the BAR type? >> >> We extend the bar size with MSI-X and use a transport flag to >> indicate that it's available, right? >> >> 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; >>> >