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Re: [PATCH v8 02/13] vpci: use per-domain PCI lock to protect vpci structure
- To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Thu, 20 Jul 2023 15:27:29 +0200
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- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Oleksandr Andrushchenko <Oleksandr_Andrushchenko@xxxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- Delivery-date: Thu, 20 Jul 2023 13:27:53 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 20.07.2023 13:20, Roger Pau Monné wrote:
> On Thu, Jul 20, 2023 at 12:32:31AM +0000, Volodymyr Babchuk wrote:
>> @@ -447,8 +476,16 @@ void vpci_write(pci_sbdf_t sbdf, unsigned int reg,
>> unsigned int size,
>>
>> /*
>> * Find the PCI dev matching the address, which for hwdom also requires
>> - * consulting DomXEN. Passthrough everything that's not trapped.
>> + * consulting DomXEN. Passthrough everything that's not trapped.
>> + * If this is hwdom, we need to hold locks for both domain in case if
>> + * modify_bars is called()
>
> Typo: the () wants to be at the end of modify_bars().
>
>> */
>> + read_lock(&d->pci_lock);
>> +
>> + /* dom_xen->pci_lock always should be taken second to prevent deadlock
>> */
>> + if ( is_hardware_domain(d) )
>> + read_lock(&dom_xen->pci_lock);
>
> For modify_bars() we also want the locks to be in write mode (at least
> the hw one), so that the position of the BARs can't be changed while
> modify_bars() is iterating over them.
Isn't changing of the BARs happening under the vpci lock? Or else I guess
I haven't understood the description correctly: My reading so far was
that it is only the presence (allocation status / pointer validity) that
is protected by this new lock.
Jan
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