On Tue, Sep 19, 2023 at 12:20:39PM -0400, Stewart Hildebrand wrote:
> On 9/19/23 11:39, Roger Pau Monné wrote:
> > On Tue, Aug 29, 2023 at 11:19:42PM +0000, Volodymyr Babchuk wrote:
> >> diff --git a/xen/drivers/vpci/msi.c b/xen/drivers/vpci/msi.c
> >> index 8f2b59e61a..a0733bb2cb 100644
> >> --- a/xen/drivers/vpci/msi.c
> >> +++ b/xen/drivers/vpci/msi.c
> >> @@ -318,15 +321,28 @@ void vpci_dump_msi(void)
> >> * holding the lock.
> >> */
> >> printk("unable to print all MSI-X entries: %d\n", rc);
> >> - process_pending_softirqs();
> >> - continue;
> >> + goto pdev_done;
> >> }
> >> }
> >>
> >> spin_unlock(&pdev->vpci->lock);
> >> + pdev_done:
> >> + /*
> >> + * Unlock lock to process pending softirqs. This is
> >> + * potentially unsafe, as d->pdev_list can be changed in
> >> + * meantime.
> >> + */
> >> + read_unlock(&d->pci_lock);
> >> process_pending_softirqs();
> >> + if ( !read_trylock(&d->pci_lock) )
> >> + {
> >> + printk("unable to access other devices for the domain\n");
> >> + goto domain_done;
> >
> > Shouldn't the domain_done label be after the read_unlock(), so that we
> > can proceed to try to dump the devices for the next domain? With the
> > proposed code a failure to acquire one of the domains pci_lock
> > terminates the dump.
> >
> >> + }
> >> }
> >> + read_unlock(&d->pci_lock);
> >> }
> >> + domain_done:
> >> rcu_read_unlock(&domlist_read_lock);
> >> }
> >>
>
> With the label moved, a no-op expression after the label is needed to make
> the compiler happy:
>
> }
> }
> read_unlock(&d->pci_lock);
> domain_done:
> (void)0;
> }
> rcu_read_unlock(&domlist_read_lock);
> }
>
>
> If the no-op is omitted, the compiler may complain (gcc 9.4.0):
>
> drivers/vpci/msi.c: In function ‘vpci_dump_msi’:
> drivers/vpci/msi.c:351:2: error: label at end of compound statement
> 351 | domain_done:
> | ^~~~~~~~~~~
Might be better to place the label at the start of the loop, and
likely rename to next_domain.
Thanks, Roger.
