Messages in this thread Patch in this message | | | Subject | Re: [PATCH RFC don't apply] vdpa_sim: endian-ness for config space | From | Jason Wang <> | Date | Thu, 16 Jul 2020 15:42:52 +0800 |
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On 2020/7/16 下午1:42, Michael S. Tsirkin wrote: > On Wed, Jul 15, 2020 at 10:02:32PM +0800, Jason Wang wrote: >> On 2020/7/15 下午9:58, Michael S. Tsirkin wrote: >>> VDPA sim stores config space as native endian, but that >>> is wrong: modern guests expect LE. >>> I coded up the following to fix it up, but it is wrong too: >>> vdpasim_create is called before guest features are known. >>> >>> So what should we do? New ioctl to specify the interface used? >>> More ideas? >>> >>> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> >> >> Can we do the endian conversion in set_config/get_config()? >> >> Thanks > That is problematic at least from static checking point of view.
I don't get here. I thought it's just leXX_to_cpu() conversion in set_config()/get_config() as what is done in MMIO's vm_set/vm_get.
> It would be reasonable to do it in vdpasim_set_features, except > legacy guests might not set features at all. > So my proposal is: > - set config in vdpasim_set_features
Just to make sure I understand here. What's the meaning of "set config" do you mean setup the config space? If yes, and if there's a device config space, we still need to do the endian conversion?
> - document that this is where devices should initialize config > - vdpa core will maintain a "features set" flag, if get/set config > is called without set features, core will call set features > automatically with 0 value.
Ok, I think you meant checking FEATURE_OK via get_status in vDPA core?
Thanks
> > Thoughts? > > >>> >>> --- >>> drivers/vdpa/vdpa_sim/vdpa_sim.c | 22 ++++++++++++++++++++-- >>> 1 file changed, 20 insertions(+), 2 deletions(-) >>> >>> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c >>> index a9bc5e0fb353..cc754ae0ec15 100644 >>> --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c >>> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c >>> @@ -24,6 +24,7 @@ >>> #include <linux/etherdevice.h> >>> #include <linux/vringh.h> >>> #include <linux/vdpa.h> >>> +#include <linux/virtio_byteorder.h> >>> #include <linux/vhost_iotlb.h> >>> #include <uapi/linux/virtio_config.h> >>> #include <uapi/linux/virtio_net.h> >>> @@ -72,6 +73,23 @@ struct vdpasim { >>> u64 features; >>> }; >>> +/* TODO: cross-endian support */ >>> +static inline bool vdpasim_is_little_endian(struct vdpasim *vdpasim) >>> +{ >>> + return virtio_legacy_is_little_endian() || >>> + (vdpasim->features & (1ULL << VIRTIO_F_VERSION_1)); >>> +} >>> + >>> +static inline u16 vdpasim16_to_cpu(struct vdpasim *vdpasim, __virtio16 val) >>> +{ >>> + return __virtio16_to_cpu(vdpasim_is_little_endian(vdpasim), val); >>> +} >>> + >>> +static inline __virtio16 cpu_to_vdpasim16(struct vdpasim *vdpasim, u16 val) >>> +{ >>> + return __cpu_to_virtio16(vdpasim_is_little_endian(vdpasim), val); >>> +} >>> + >>> static struct vdpasim *vdpasim_dev; >>> static struct vdpasim *vdpa_to_sim(struct vdpa_device *vdpa) >>> @@ -332,8 +350,8 @@ static struct vdpasim *vdpasim_create(void) >>> goto err_iommu; >>> config = &vdpasim->config; >>> - config->mtu = 1500; >>> - config->status = VIRTIO_NET_S_LINK_UP; >>> + config->mtu = cpu_to_vdpasim16(vdpasim, 1500); >>> + config->status = cpu_to_vdpasim16(vdpasim, VIRTIO_NET_S_LINK_UP); >>> eth_random_addr(config->mac); >>> vringh_set_iotlb(&vdpasim->vqs[0].vring, vdpasim->iommu);
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