Re: [PATCH] vpci: Add resizable bar support

["Roger Pau Monné" <roger.pau@citrix.com>]

On Wed, Nov 13, 2024 at 04:00:27PM +0800, Jiqian Chen wrote:
> +static void cf_check rebar_ctrl_write(const struct pci_dev *pdev,
> +                                      unsigned int reg,
> +                                      uint32_t val,
> +                                      void *data)
> +{
> +    uint32_t ctrl, index;
> +    struct vpci_bar *bars = pdev->vpci->header.bars;
> +
> +    ctrl = pci_conf_read32(pdev->sbdf, reg);
> +    if ( ctrl == val )
> +        return;
> +
> +    ctrl &= ~PCI_REBAR_CTRL_BAR_SIZE;
> +    if ( ctrl != ( val & ~PCI_REBAR_CTRL_BAR_SIZE ) )
> +        return;
> +
> +    index = ctrl & PCI_REBAR_CTRL_BAR_IDX;
> +    bars[index].size = (1 << ((val & PCI_REBAR_CTRL_BAR_SIZE) >>
> +                              PCI_REBAR_CTRL_BAR_SHIFT)) *
> +                       PCI_REBAR_CTRL_BAR_UNIT;

One further comment: you also need to reset addr and guest_addr here
(possibly by reading them from the BAR register), as the specification
states that:

"After writing the BAR Size field, the contents of the corresponding
BAR are undefined"

Hence the cached addr and guest_addr are stale after a write to the
control register.

Thanks, Roger.