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Re: [PATCH v9 04/16] vpci: add hooks for PCI device assign/de-assign
- To: Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Wed, 13 Sep 2023 07:58:01 +0200
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- Cc: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>, Oleksandr Andrushchenko <Oleksandr_Andrushchenko@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Paul Durrant <paul@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Wed, 13 Sep 2023 05:58:20 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 13.09.2023 01:41, Volodymyr Babchuk wrote:
> Jan Beulich <jbeulich@xxxxxxxx> writes:
>> On 30.08.2023 01:19, Volodymyr Babchuk wrote:
>>> @@ -1481,6 +1488,13 @@ static int assign_device(struct domain *d, u16 seg,
>>> u8 bus, u8 devfn, u32 flag)
>>> if ( pdev->broken && d != hardware_domain && d != dom_io )
>>> goto done;
>>>
>>> + if ( IS_ENABLED(CONFIG_HAS_VPCI_GUEST_SUPPORT) )
>>> + {
>>> + write_lock(&pdev->domain->pci_lock);
>>> + vpci_deassign_device(pdev);
>>> + write_unlock(&pdev->domain->pci_lock);
>>> + }
>>
>> Why is the DomIO special case ...
>
> vpci_deassign_device() does nothing if vPCI was initialized for a
> domain. So it not wrong to call this function even if pdev belongs to dom_io.
Well, okay, but then you acquire a lock just to do nothing (apart
from the apparent asymmetry).
>>> @@ -1506,6 +1520,15 @@ static int assign_device(struct domain *d, u16 seg,
>>> u8 bus, u8 devfn, u32 flag)
>>> rc = iommu_call(hd->platform_ops, assign_device, d, devfn,
>>> pci_to_dev(pdev), flag);
>>> }
>>> + if ( rc )
>>> + goto done;
>>> +
>>> + if ( IS_ENABLED(CONFIG_HAS_VPCI_GUEST_SUPPORT) && d != dom_io)
>>> + {
>>> + write_lock(&d->pci_lock);
>>> + rc = vpci_assign_device(pdev);
>>> + write_unlock(&d->pci_lock);
>>> + }
>>
>> ... relevant only here?
>>
>
> There is no sense to initialize vPCI for dom_io.
Of course.
Jan
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