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Re: [Qemu-devel] [RfC PATCH 04/15] virtio-pci: make modern bar 64bit pre
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [RfC PATCH 04/15] virtio-pci: make modern bar 64bit prefetchable |
Date: |
Mon, 2 Mar 2015 13:33:31 +0100 |
On Mon, Feb 23, 2015 at 11:23:20AM +0100, Gerd Hoffmann wrote:
> Modern bar is made prefetchable. In case it is configured to use one of
> the bars 0, 2, or 4 (which by default is the case) it is also configured
> as 64bit region.
>
> Signed-off-by: Gerd Hoffmann <address@hidden>
Fine, but I can't apply this without 3/15.
> ---
> hw/virtio/virtio-pci.c | 12 +++++++++---
> 1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index f97baf2..96b3692 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -1263,7 +1263,8 @@ static void virtio_pci_device_plugged(DeviceState *d)
> pci_set_word(config + PCI_DEVICE_ID,
> 0x1040 + virtio_bus_get_vdev_id(bus));
> pci_config_set_revision(config, 1);
> - if (proxy->msix_bar == proxy->modern_mem_bar) {
> + if ((proxy->msix_bar == proxy->modern_mem_bar) ||
> + (proxy->msix_bar == proxy->modern_mem_bar+1)) {
> proxy->msix_bar = (proxy->msix_bar + 2) % 6;
> }
> }
I'd like to avoid extra (), and see space around +.
E.g.
if (proxy->msix_bar == proxy->modern_mem_bar ||
proxy->msix_bar == proxy->modern_mem_bar + 1)
we can generally rely on C to DTRT wrt priority of arithmentic
operations and comparisons.
> @@ -1301,6 +1302,7 @@ static void virtio_pci_device_plugged(DeviceState *d)
> VIRTIO_PCI_QUEUE_MAX),
> .notify_off_multiplier =
> cpu_to_le32(QEMU_VIRTIO_PCI_QUEUE_MEM_MULT),
> };
> + uint32_t modern_mem_attr;
>
> static const MemoryRegionOps common_ops = {
> .read = virtio_pci_common_read,
> @@ -1374,9 +1376,13 @@ static void virtio_pci_device_plugged(DeviceState *d)
> QEMU_VIRTIO_PCI_QUEUE_MEM_MULT *
> VIRTIO_PCI_QUEUE_MAX);
> memory_region_add_subregion(&proxy->modern_bar, 0x3000,
> &proxy->notify);
> + modern_mem_attr = (PCI_BASE_ADDRESS_SPACE_MEMORY |
> + PCI_BASE_ADDRESS_MEM_PREFETCH);
no need for () to the right of =.
> + if (!(proxy->modern_mem_bar % 2)) {
> + modern_mem_attr |= PCI_BASE_ADDRESS_MEM_TYPE_64;
> + }
That's pretty unexpected.
This kind of hack seems to show why it's not a good idea
to let device play with layouts.
> pci_register_bar(&proxy->pci_dev, proxy->modern_mem_bar,
> - PCI_BASE_ADDRESS_SPACE_MEMORY,
> - &proxy->modern_bar);
> + modern_mem_attr, &proxy->modern_bar);
> }
>
> if (proxy->nvectors &&
> --
> 1.8.3.1
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