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

["Chen, Jiqian" <Jiqian.Chen@xxxxxxx>]

On 2025/5/8 17:39, Roger Pau Monné wrote:
> 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@xxxxxxx>
>> ---
>> cc: "Roger Pau Monné" <roger.pau@xxxxxxxxxx>
>> ---
>> 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)
By the way, I will rename this to be cleanup_rebar since the hook name will be 
changed in next version.

>> +{
>> +    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.
Yes, we don't expect that.
Will add an ASSERT_UNREACHABLE() here in next version.

> 
>> +        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.
Got it, will change.

> 
>>          }
>>  
>>          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.
Will change to -ENXIO, it seems more suitable.
Thanks.

> 
> Overall looks good.
> 
> Thanks, Roger.

-- 
Best regards,
Jiqian Chen.