Re: [PATCH v3 09/11] vpci/rebar: Remove registers when init_rebar() fails

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

On Mon, Apr 21, 2025 at 02:19:01PM +0800, Jiqian Chen wrote:
> When init_rebar() fails, the previous new changes will hide Rebar
> capability, it can't rely on vpci_deassign_device() to remove all
> Rebar related registers anymore, those registers must be removed
> fini_rebar().
> 
> To do that, call vpci_remove_registers() to remove all possible
> registered registers.
> 
> Signed-off-by: Jiqian Chen <Jiqian.Chen@amd.com>
> ---
> cc: "Roger Pau Monné" <roger.pau@citrix.com>
> ---
> v2->v3 changes:
> * Use fini_rebar() to remove all register instead of in the failure path of init_rebar();
> 
> v1->v2 changes:
> * Called vpci_remove_registers() to remove all possible registered registers instead of using a array to record all registered register.
> 
> Best regards,
> Jiqian Chen.
> ---
>  xen/drivers/vpci/rebar.c | 35 ++++++++++++++++++++++++-----------
>  1 file changed, 24 insertions(+), 11 deletions(-)
> 
> diff --git a/xen/drivers/vpci/rebar.c b/xen/drivers/vpci/rebar.c
> index 026f8f7972d9..325090afb0f8 100644
> --- a/xen/drivers/vpci/rebar.c
> +++ b/xen/drivers/vpci/rebar.c
> @@ -49,6 +49,26 @@ static void cf_check rebar_ctrl_write(const struct pci_dev *pdev,
>      bar->guest_addr = bar->addr;
>  }
>  
> +static void fini_rebar(struct pci_dev *pdev)
> +{
> +    uint32_t ctrl;
> +    unsigned int nbars;
> +    unsigned int rebar_offset = pci_find_ext_capability(pdev->sbdf,
> +                                                        PCI_EXT_CAP_ID_REBAR);
> +
> +    if ( !rebar_offset || !is_hardware_domain(pdev->domain) )

Maybe add an ASSERT_UNREACHABLE() here?  I don't think we are expected
to get into the cleanup function for the capability if it's not
present, or if the owner of the device is not the hardware domain.

> +        return;
> +
> +    ctrl = pci_conf_read32(pdev->sbdf, rebar_offset + PCI_REBAR_CTRL(0));
> +    nbars = MASK_EXTR(ctrl, PCI_REBAR_CTRL_NBAR_MASK);
> +    /*
> +     * Remove all possible registered registers except header.
> +     * Header register will be removed in mask function.
> +     */
> +    vpci_remove_registers(pdev->vpci, rebar_offset + PCI_REBAR_CAP(0),
> +                          PCI_REBAR_CTRL(nbars - 1));
> +}
> +
>  static int cf_check init_rebar(struct pci_dev *pdev)
>  {
>      uint32_t ctrl;
> @@ -80,7 +100,7 @@ static int cf_check init_rebar(struct pci_dev *pdev)
>          {
>              printk(XENLOG_ERR "%pd %pp: too big BAR number %u in REBAR_CTRL\n",
>                     pdev->domain, &pdev->sbdf, index);
> -            continue;
> +            return -EINVAL;

-E2BIG might be better here.  In general I try to avoid using EINVAL,
as it's a catch all that makes differentiating error later on harder.

>          }
>  
>          bar = &pdev->vpci->header.bars[index];
> @@ -88,7 +108,7 @@ static int cf_check init_rebar(struct pci_dev *pdev)
>          {
>              printk(XENLOG_ERR "%pd %pp: BAR%u is not in memory space\n",
>                     pdev->domain, &pdev->sbdf, index);
> -            continue;
> +            return -EINVAL;

Maybe -EDOM here?  -ENXIO or EIO might also be appropriate.

Overall looks good.

Thanks, Roger.