Linux Virtualization - Aug 2020 - [PATCH v2 22/24] vdpa_sim: fix endian-ness of config space

On 2020/8/4 ??5:00, Michael S. Tsirkin wrote:
> VDPA sim accesses config space as native endian - this is
> wrong since it's a modern device and actually uses LE.
>
> It only supports modern guests so we could punt and
> just force LE, but let's use the full virtio APIs since people
> tend to copy/paste code, and this is not data path anyway.
>
> Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
> ---
>   drivers/vdpa/vdpa_sim/vdpa_sim.c | 31 ++++++++++++++++++++++++++-----
>   1 file changed, 26 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c
b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> index a9bc5e0fb353..fa05e065ff69 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)
> @@ -306,7 +324,6 @@ static const struct vdpa_config_ops
vdpasim_net_config_ops;
>   
>   static struct vdpasim *vdpasim_create(void)
>   {
> -	struct virtio_net_config *config;
>   	struct vdpasim *vdpasim;
>   	struct device *dev;
>   	int ret = -ENOMEM;
> @@ -331,10 +348,7 @@ static struct vdpasim *vdpasim_create(void)
>   	if (!vdpasim->buffer)
>   		goto err_iommu;
>   
> -	config = &vdpasim->config;
> -	config->mtu = 1500;
> -	config->status = VIRTIO_NET_S_LINK_UP;
> -	eth_random_addr(config->mac);
> +	eth_random_addr(vdpasim->config.mac);
>   
>   	vringh_set_iotlb(&vdpasim->vqs[0].vring, vdpasim->iommu);
>   	vringh_set_iotlb(&vdpasim->vqs[1].vring, vdpasim->iommu);
> @@ -448,6 +462,7 @@ static u64 vdpasim_get_features(struct vdpa_device
*vdpa)
>   static int vdpasim_set_features(struct vdpa_device *vdpa, u64 features)
>   {
>   	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
> +	struct virtio_net_config *config = &vdpasim->config;
>   
>   	/* DMA mapping must be done by driver */
>   	if (!(features & (1ULL << VIRTIO_F_ACCESS_PLATFORM)))
> @@ -455,6 +470,12 @@ static int vdpasim_set_features(struct vdpa_device
*vdpa, u64 features)
>   
>   	vdpasim->features = features & vdpasim_features;
>   
> +	/* We only know whether guest is using the legacy interface here, so
> +	 * that's the earliest we can set config fields.
> +	 */

We check whether or not ACCESS_PLATFORM is set before which is probably 
a hint that only modern device is supported. So I wonder just force LE 
and fail if VERSION_1 is not set is better?

Thanks

> +
> +	config->mtu = cpu_to_vdpasim16(vdpasim, 1500);
> +	config->status = cpu_to_vdpasim16(vdpasim, VIRTIO_NET_S_LINK_UP);
>   	return 0;
>   }
>

On Wed, Aug 05, 2020 at 02:21:07PM +0800, Jason Wang
wrote:
> 
> On 2020/8/4 ??5:00, Michael S. Tsirkin wrote:
> > VDPA sim accesses config space as native endian - this is
> > wrong since it's a modern device and actually uses LE.
> > 
> > It only supports modern guests so we could punt and
> > just force LE, but let's use the full virtio APIs since people
> > tend to copy/paste code, and this is not data path anyway.
> > 
> > Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
> > ---
> >   drivers/vdpa/vdpa_sim/vdpa_sim.c | 31
++++++++++++++++++++++++++-----
> >   1 file changed, 26 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c
b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> > index a9bc5e0fb353..fa05e065ff69 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)
> > @@ -306,7 +324,6 @@ static const struct vdpa_config_ops
vdpasim_net_config_ops;
> >   static struct vdpasim *vdpasim_create(void)
> >   {
> > -	struct virtio_net_config *config;
> >   	struct vdpasim *vdpasim;
> >   	struct device *dev;
> >   	int ret = -ENOMEM;
> > @@ -331,10 +348,7 @@ static struct vdpasim *vdpasim_create(void)
> >   	if (!vdpasim->buffer)
> >   		goto err_iommu;
> > -	config = &vdpasim->config;
> > -	config->mtu = 1500;
> > -	config->status = VIRTIO_NET_S_LINK_UP;
> > -	eth_random_addr(config->mac);
> > +	eth_random_addr(vdpasim->config.mac);
> >   	vringh_set_iotlb(&vdpasim->vqs[0].vring, vdpasim->iommu);
> >   	vringh_set_iotlb(&vdpasim->vqs[1].vring, vdpasim->iommu);
> > @@ -448,6 +462,7 @@ static u64 vdpasim_get_features(struct vdpa_device
*vdpa)
> >   static int vdpasim_set_features(struct vdpa_device *vdpa, u64
features)
> >   {
> >   	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
> > +	struct virtio_net_config *config = &vdpasim->config;
> >   	/* DMA mapping must be done by driver */
> >   	if (!(features & (1ULL << VIRTIO_F_ACCESS_PLATFORM)))
> > @@ -455,6 +470,12 @@ static int vdpasim_set_features(struct
vdpa_device *vdpa, u64 features)
> >   	vdpasim->features = features & vdpasim_features;
> > +	/* We only know whether guest is using the legacy interface here, so
> > +	 * that's the earliest we can set config fields.
> > +	 */
> 
> 
> We check whether or not ACCESS_PLATFORM is set before which is probably a
> hint that only modern device is supported. So I wonder just force LE and
> fail if VERSION_1 is not set is better?
> 
> Thanks
> 
Hmm good point. As usual legacy does not have a clean way to fail though,
are we sure we don't ever want to support legacy guests?

> > +
> > +	config->mtu = cpu_to_vdpasim16(vdpasim, 1500);
> > +	config->status = cpu_to_vdpasim16(vdpasim, VIRTIO_NET_S_LINK_UP);
> >   	return 0;
> >   }

On Wed, Aug 05, 2020 at 02:21:07PM +0800, Jason Wang
wrote:
> 
> On 2020/8/4 ??5:00, Michael S. Tsirkin wrote:
> > VDPA sim accesses config space as native endian - this is
> > wrong since it's a modern device and actually uses LE.
> > 
> > It only supports modern guests so we could punt and
> > just force LE, but let's use the full virtio APIs since people
> > tend to copy/paste code, and this is not data path anyway.
> > 
> > Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
> > ---
> >   drivers/vdpa/vdpa_sim/vdpa_sim.c | 31
++++++++++++++++++++++++++-----
> >   1 file changed, 26 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c
b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> > index a9bc5e0fb353..fa05e065ff69 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)
> > @@ -306,7 +324,6 @@ static const struct vdpa_config_ops
vdpasim_net_config_ops;
> >   static struct vdpasim *vdpasim_create(void)
> >   {
> > -	struct virtio_net_config *config;
> >   	struct vdpasim *vdpasim;
> >   	struct device *dev;
> >   	int ret = -ENOMEM;
> > @@ -331,10 +348,7 @@ static struct vdpasim *vdpasim_create(void)
> >   	if (!vdpasim->buffer)
> >   		goto err_iommu;
> > -	config = &vdpasim->config;
> > -	config->mtu = 1500;
> > -	config->status = VIRTIO_NET_S_LINK_UP;
> > -	eth_random_addr(config->mac);
> > +	eth_random_addr(vdpasim->config.mac);
> >   	vringh_set_iotlb(&vdpasim->vqs[0].vring, vdpasim->iommu);
> >   	vringh_set_iotlb(&vdpasim->vqs[1].vring, vdpasim->iommu);
> > @@ -448,6 +462,7 @@ static u64 vdpasim_get_features(struct vdpa_device
*vdpa)
> >   static int vdpasim_set_features(struct vdpa_device *vdpa, u64
features)
> >   {
> >   	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
> > +	struct virtio_net_config *config = &vdpasim->config;
> >   	/* DMA mapping must be done by driver */
> >   	if (!(features & (1ULL << VIRTIO_F_ACCESS_PLATFORM)))
> > @@ -455,6 +470,12 @@ static int vdpasim_set_features(struct
vdpa_device *vdpa, u64 features)
> >   	vdpasim->features = features & vdpasim_features;
> > +	/* We only know whether guest is using the legacy interface here, so
> > +	 * that's the earliest we can set config fields.
> > +	 */
> 
> 
> We check whether or not ACCESS_PLATFORM is set before which is probably a
> hint that only modern device is supported. So I wonder just force LE and
> fail if VERSION_1 is not set is better?
> 
> Thanks
So how about I add a comment along the lines of

/*
 * vdpasim ATM requires VIRTIO_F_ACCESS_PLATFORM, so we don't need to
 * support legacy guests. Keep transitional device code around for
 * the benefit of people who might copy-and-paste this into transitional
 * device code.
 */

> 
> > +
> > +	config->mtu = cpu_to_vdpasim16(vdpasim, 1500);
> > +	config->status = cpu_to_vdpasim16(vdpasim, VIRTIO_NET_S_LINK_UP);
> >   	return 0;
> >   }

On 2020/8/5 ??8:06, Michael S. Tsirkin wrote:
> On Wed, Aug 05, 2020 at 02:21:07PM +0800, Jason Wang wrote:
>> On 2020/8/4 ??5:00, Michael S. Tsirkin wrote:
>>> VDPA sim accesses config space as native endian - this is
>>> wrong since it's a modern device and actually uses LE.
>>>
>>> It only supports modern guests so we could punt and
>>> just force LE, but let's use the full virtio APIs since people
>>> tend to copy/paste code, and this is not data path anyway.
>>>
>>> Signed-off-by: Michael S. Tsirkin<mst at redhat.com>
>>> ---
>>>    drivers/vdpa/vdpa_sim/vdpa_sim.c | 31
++++++++++++++++++++++++++-----
>>>    1 file changed, 26 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c
b/drivers/vdpa/vdpa_sim/vdpa_sim.c
>>> index a9bc5e0fb353..fa05e065ff69 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)
>>> @@ -306,7 +324,6 @@ static const struct vdpa_config_ops
vdpasim_net_config_ops;
>>>    static struct vdpasim *vdpasim_create(void)
>>>    {
>>> -	struct virtio_net_config *config;
>>>    	struct vdpasim *vdpasim;
>>>    	struct device *dev;
>>>    	int ret = -ENOMEM;
>>> @@ -331,10 +348,7 @@ static struct vdpasim *vdpasim_create(void)
>>>    	if (!vdpasim->buffer)
>>>    		goto err_iommu;
>>> -	config = &vdpasim->config;
>>> -	config->mtu = 1500;
>>> -	config->status = VIRTIO_NET_S_LINK_UP;
>>> -	eth_random_addr(config->mac);
>>> +	eth_random_addr(vdpasim->config.mac);
>>>    	vringh_set_iotlb(&vdpasim->vqs[0].vring,
vdpasim->iommu);
>>>    	vringh_set_iotlb(&vdpasim->vqs[1].vring,
vdpasim->iommu);
>>> @@ -448,6 +462,7 @@ static u64 vdpasim_get_features(struct
vdpa_device *vdpa)
>>>    static int vdpasim_set_features(struct vdpa_device *vdpa, u64
features)
>>>    {
>>>    	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
>>> +	struct virtio_net_config *config = &vdpasim->config;
>>>    	/* DMA mapping must be done by driver */
>>>    	if (!(features & (1ULL << VIRTIO_F_ACCESS_PLATFORM)))
>>> @@ -455,6 +470,12 @@ static int vdpasim_set_features(struct
vdpa_device *vdpa, u64 features)
>>>    	vdpasim->features = features & vdpasim_features;
>>> +	/* We only know whether guest is using the legacy interface here,
so
>>> +	 * that's the earliest we can set config fields.
>>> +	 */
>> We check whether or not ACCESS_PLATFORM is set before which is probably
a
>> hint that only modern device is supported. So I wonder just force LE
and
>> fail if VERSION_1 is not set is better?
>>
>> Thanks
> So how about I add a comment along the lines of
>
> /*
>   * vdpasim ATM requires VIRTIO_F_ACCESS_PLATFORM, so we don't need to
>   * support legacy guests. Keep transitional device code around for
>   * the benefit of people who might copy-and-paste this into transitional
>   * device code.
>   */

That's fine.

Thanks

>
>