On Wed, 2014-10-22 at 15:54 +0200, Antonios Motakis wrote:
> On Tue, Oct 21, 2014 at 6:34 PM, Alex Williamson
> <alex.williamson@xxxxxxxxxx> wrote:
> > On Mon, 2014-10-13 at 15:10 +0200, Antonios Motakis wrote:
> >> This patch enables the IOCTLs VFIO_DEVICE_GET_REGION_INFO ioctl call,
> >> which allows the user to learn about the available MMIO resources of
> >> a device.
> >>
> >> Signed-off-by: Antonios Motakis <a.motakis@xxxxxxxxxxxxxxxxxxxxxx>
> >> ---
> >> drivers/vfio/platform/vfio_platform_common.c | 93 +++++++++++++++++++++++++--
> >> drivers/vfio/platform/vfio_platform_private.h | 22 +++++++
> >> 2 files changed, 111 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/drivers/vfio/platform/vfio_platform_common.c b/drivers/vfio/platform/vfio_platform_common.c
> >> index 1e4073f..8a7e474 100644
> >> --- a/drivers/vfio/platform/vfio_platform_common.c
> >> +++ b/drivers/vfio/platform/vfio_platform_common.c
> >> @@ -27,17 +27,84 @@
> >>
> >> #include "vfio_platform_private.h"
> >>
> >> +static int vfio_platform_regions_init(struct vfio_platform_device *vdev)
> >> +{
> >> + int cnt = 0, i;
> >> +
> >> + while (vdev->get_resource(vdev, cnt))
> >> + cnt++;
> >> +
> >> + vdev->regions = kcalloc(cnt, sizeof(struct vfio_platform_region),
> >> + GFP_KERNEL);
> >> + if (!vdev->regions)
> >> + return -ENOMEM;
> >> +
> >> + for (i = 0; i < cnt; i++) {
> >> + struct resource *res =
> >> + vdev->get_resource(vdev, i);
> >> +
> >> + if (!res)
> >> + goto err;
> >> +
> >> + vdev->regions[i].addr = res->start;
> >> + vdev->regions[i].size = resource_size(res);
> >> + vdev->regions[i].flags = 0;
> >> +
> >> + switch (resource_type(res)) {
> >> + case IORESOURCE_MEM:
> >> + vdev->regions[i].type = VFIO_PLATFORM_REGION_TYPE_MMIO;
> >> + break;
> >> + case IORESOURCE_IO:
> >> + vdev->regions[i].type = VFIO_PLATFORM_REGION_TYPE_PIO;
> >> + break;
> >
> > Ok, we have support for PIO in platform now (thanks!), does the user
> > know what type of region they're dealing with? Do they care? For PCI
> > the user tests the PCI BAR in config space to determine which type it
> > is. I'm guessing that platform would do something similar against the
> > device tree or ACPI, right?
>
> Maybe is worthwhile to add an explicit flag in
> VFIO_DEVICE_GET_REGION_INFO for PIO regions. For platform devices I
> don't know if we can always rely on DT or ACPI info to be available.
> For VFIO PCI the BAR is always implemented, and while I have proposed
> an RFC to return DT information, I don't think we can assume how a
> device is described in the host, whether DT, ACPI, or dark magic.
Is this already handled by the fact that vfio-platform is not meant to
be a generic meta driver to the same extent as vfio-pci? There is no
self-describing config space on platform devices like there is on PCI,
so the user will need to know in advance somehow what the device is and
what resources/irqs it uses. We do need to make sure though that we
provide a userspace ABI that allows them to match VFIO indexes to the
device in a predictable way. It's not fully clear to me how that works.
Thanks,
Alex
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