<please use plain-text next time>
> From: Yishai Hadas <yishaih@xxxxxxxxxx>
> Sent: Thursday, July 21, 2022 7:06 PM
> > > +/*
> > > + * Upon VFIO_DEVICE_FEATURE_SET start device DMA logging.
> >
> > both 'start'/'stop' are via VFIO_DEVICE_FEATURE_SET
>
> Right, we have a note for that near VFIO_DEVICE_FEATURE_DMA_LOGGING_STOP.
> Here it refers to the start option.
let's make it accurate here.
> > > + * page_size is an input that hints what tracking granularity the device
> > > + * should try to achieve. If the device cannot do the hinted page size then it
> > > + * should pick the next closest page size it supports. On output the device
> >
> > next closest 'smaller' page size?
>
> Not only, it depends on the device capabilities/support and should be a driver choice.
'should pick next closest" is a guideline to the driver. If user requests
8KB while the device supports 4KB and 16KB, which one is closest?
It's probably safer to just say that it's a driver choice when the hinted page
size cannot be set?
> > > +struct vfio_device_feature_dma_logging_control {
> > > + __aligned_u64 page_size;
> > > + __u32 num_ranges;
> > > + __u32 __reserved;
> > > + __aligned_u64 ranges;
> > > +};
> >
> > should we move the definition of LOG_MAX_RANGES to be here
> > so the user can know the max limits of tracked ranges?
> This was raised as an option as part of this mail thread.
> However, for now it seems redundant as we may not expect user space to hit this limit and it mainly comes to protect kernel from memory exploding by a malicious user.
No matter how realistic an user might hit an limitation, it doesn't
sound good to not expose it if existing.
> > > +
> > > +struct vfio_device_feature_dma_logging_range {
> > > + __aligned_u64 iova;
> > > + __aligned_u64 length;
> > > +};
> > > +
> > > +#define VFIO_DEVICE_FEATURE_DMA_LOGGING_START 3
> >
> > Can the user update the range list by doing another START?
>
> No, single start to ask the device what to track and a matching single stop should follow at the end.
let's document it then.
Thanks
Kevin
