From: Leon Romanovsky
> Sent: 11 October 2022 12:37
>
> On Tue, Oct 11, 2022 at 07:23:25PM +0800, Rui Ma wrote:
> > In some certain SR-IOV scene, when the device physical space(such as Video
> > RAM)is fixed, as the number of VFs increases, some device driver may decrease
> > actual BAR memory space used by each VF. However, the VF BAR memory mapping is
> > always based on the usual BAR probing algorithm in PCIe spec. So do not map this
> > unneeded memory can save host memory which occupied by PTEs. Although each PTE
> > only occupies a few bytes of space on its own, a large number of PTEs can still
> > take up a lot of space.
...
> > + /*
> > + * Some SR-IOV device's BAR map range is larger than they can actually use.
> > + * This extra BAR space occupy too much reverse mapping size(physical page
> > + * back to the PTEs). So add a divisor shift parameter to resize the request
> > + * resource of VF according to num of VFs.
> > + */
> > + u16 shift = 1;
Why u16??
> > + virtfn->resource[i].end = virtfn->resource[i].start + (size >> (shift - 1)) - 1;
The 'shift - 1' may require a mask.
...
> > +struct virtfn_get_shift_methods {
> > + u16 vendor;
> > + u16 device;
> > + u16 (*get_shift)(struct pci_dev *dev, u16 arg, int arg2);
More pointless u16 - they just make the code larger.
...
> > +static inline u16 virtfn_get_shift(struct pci_dev *dev, u16 arg1, int arg2)
> > +{
> > + return (u16)1;
>
> <...>
>
> > + return (u16)1;
>
> Why do you need these casts? You can omit them.
Kill all the u16
David
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