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Re: [PATCH v2 4/4] vPCI/DomU: really no ext-caps without extended config space
- To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Thu, 29 Jan 2026 12:36:09 +0100
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- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
- Delivery-date: Thu, 29 Jan 2026 11:36:34 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 29.01.2026 11:51, Roger Pau Monné wrote:
> On Thu, Jan 29, 2026 at 11:08:22AM +0100, Jan Beulich wrote:
>> On 29.01.2026 10:19, Roger Pau Monné wrote:
>>> On Mon, Jan 19, 2026 at 03:48:01PM +0100, Jan Beulich wrote:
>>>> --- a/xen/drivers/vpci/header.c
>>>> +++ b/xen/drivers/vpci/header.c
>>>> @@ -830,9 +830,14 @@ static int vpci_init_ext_capability_list
>>>> unsigned int pos = PCI_CFG_SPACE_SIZE;
>>>>
>>>> if ( !is_hardware_domain(pdev->domain) )
>>>> + {
>>>> + if ( !pdev->ext_cfg )
>>>> + return 0;
>>>
>>> Don't you want to possibly put this as a top-level check, so if
>>> there's no extended config space we avoid doing the PCI_CFG_SPACE_SIZE
>>> read for dom0 also?
>>
>> Hmm, yes, didn't think about that. That'll mean dropping the
>> "if ( pos != PCI_CFG_SPACE_SIZE )" from the body of the
>> "if ( header == 0xffffffffU )" then, i.e. the printk() there becoming
>> unconditional. It may also mean dropping "DomU" from the subject.
>
> I've also wondered whether we want to short-circuit vpci_{read,write}
> accesses if the device doesn't have extended cfg, for domUs to be on
> the safe side.
May make sense, yes. I don't think I'll add anything along these lines to
this series, though.
Jan
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