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SubjectRe: [RFC PATCH v4 06/10] VFIO_PLATFORM: Read and write support for the device fd
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On Tue, 2014-03-25 at 17:43 +0100, Eric Auger wrote:
> > Date: Sat, 8 Feb 2014 18:29:36 +0100
> > VFIO returns a file descriptor which we can use to manipulate the memory
> > regions of the device. Since some memory regions we cannot mmap due to
> > security concerns, we also allow to read and write to this file descriptor
> > directly.
> >
> > Signed-off-by: Antonios Motakis <a.motakis@virtualopensystems.com>
> > Tested-by: Alvise Rigo <a.rigo@virtualopensystems.com>
> > ---
> > drivers/vfio/platform/vfio_platform.c | 128 +++++++++++++++++++++++++++++++++-
> > 1 file changed, 125 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/vfio/platform/vfio_platform.c b/drivers/vfio/platform/vfio_platform.c
> > index f7db5c0..ee96078 100644
> > --- a/drivers/vfio/platform/vfio_platform.c
> > +++ b/drivers/vfio/platform/vfio_platform.c
> > @@ -55,7 +55,8 @@ static int vfio_platform_regions_init(struct vfio_platform_device *vdev)
> >
> > region.addr = res->start;
> > region.size = resource_size(res);
> > - region.flags = 0;
> > + region.flags = VFIO_REGION_INFO_FLAG_READ
> > + | VFIO_REGION_INFO_FLAG_WRITE;
> >
> > vdev->region[i] = region;
> > }
> > @@ -150,13 +151,134 @@ static long vfio_platform_ioctl(void *device_data,
> > static ssize_t vfio_platform_read(void *device_data, char __user *buf,
> > size_t count, loff_t *ppos)
> > {
> > - return 0;
> > + struct vfio_platform_device *vdev = device_data;
> > + unsigned int *io;
> > + int i;
> > +
> > + for (i = 0; i < vdev->num_regions; i++) {
> > + struct vfio_platform_region region = vdev->region[i];
> > + unsigned int done = 0;
> > + loff_t off;
> > +
> > + if ((*ppos < region.addr)
> > + || (*ppos + count - 1) >= (region.addr + region.size))
> > + continue;
> > +
> > + io = ioremap_nocache(region.addr, region.size);
> > +
> > + off = *ppos - region.addr;
> > +
> > + while (count) {
> > + size_t filled;
> > +
> > + if (count >= 4 && !(off % 4)) {
> > + u32 val;
> > +
> > + val = ioread32(io + off);
>
> Hi Antonios,
>
> I suspect there is an issue with the read address. Indeed io being an
> unsigned int* the read address is io + off x sizeof (unsigned int) ie.
> io+ offx4 whereas we expect to read io + off. declaring io as a void*
> corrects the issue (or void __iomem *io). Same issue on write.

Yep, the same code for vfio/pci uses void __iomem *io. Thanks,

Alex



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