This lock protects alldevs_list of struct pci_seg. As this, it should be used when we are adding, removing on enumerating PCI devices assigned to a PCI segment.
Radix tree that stores PCI segment has own locking mechanism, also pci_seg structures are only allocated and newer freed, so we need no additional locking to access pci_seg structures. But we need a lock that protects alldevs_list field. This enables more granular locking instead of one huge pcidevs_lock that locks entire PCI subsystem. Please note that pcidevs_lock() is still used, we are going to remove it in subsequent patches. Signed-off-by: Volodymyr Babchuk <[email protected]> --- xen/drivers/passthrough/pci.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) diff --git a/xen/drivers/passthrough/pci.c b/xen/drivers/passthrough/pci.c index 4366f8f965..2dfa1c2875 100644 --- a/xen/drivers/passthrough/pci.c +++ b/xen/drivers/passthrough/pci.c @@ -38,6 +38,7 @@ struct pci_seg { struct list_head alldevs_list; + spinlock_t alldevs_lock; u16 nr; unsigned long *ro_map; /* bus2bridge_lock protects bus2bridge array */ @@ -93,6 +94,7 @@ static struct pci_seg *alloc_pseg(u16 seg) pseg->nr = seg; INIT_LIST_HEAD(&pseg->alldevs_list); spin_lock_init(&pseg->bus2bridge_lock); + spin_lock_init(&pseg->alldevs_lock); if ( radix_tree_insert(&pci_segments, seg, pseg) ) { @@ -385,9 +387,13 @@ static struct pci_dev *alloc_pdev(struct pci_seg *pseg, u8 bus, u8 devfn) unsigned int pos; int rc; + spin_lock(&pseg->alldevs_lock); list_for_each_entry ( pdev, &pseg->alldevs_list, alldevs_list ) if ( pdev->bus == bus && pdev->devfn == devfn ) + { + spin_unlock(&pseg->alldevs_lock); return pdev; + } pdev = xzalloc(struct pci_dev); if ( !pdev ) @@ -404,10 +410,12 @@ static struct pci_dev *alloc_pdev(struct pci_seg *pseg, u8 bus, u8 devfn) if ( rc ) { xfree(pdev); + spin_unlock(&pseg->alldevs_lock); return NULL; } list_add(&pdev->alldevs_list, &pseg->alldevs_list); + spin_unlock(&pseg->alldevs_lock); /* update bus2bridge */ switch ( pdev->type = pdev_type(pseg->nr, bus, devfn) ) @@ -611,15 +619,20 @@ struct pci_dev *pci_get_pdev(struct domain *d, pci_sbdf_t sbdf) */ if ( !d || is_hardware_domain(d) ) { - const struct pci_seg *pseg = get_pseg(sbdf.seg); + struct pci_seg *pseg = get_pseg(sbdf.seg); if ( !pseg ) return NULL; + spin_lock(&pseg->alldevs_lock); list_for_each_entry ( pdev, &pseg->alldevs_list, alldevs_list ) if ( pdev->sbdf.bdf == sbdf.bdf && (!d || pdev->domain == d) ) + { + spin_unlock(&pseg->alldevs_lock); return pdev; + } + spin_unlock(&pseg->alldevs_lock); } else { @@ -893,6 +906,7 @@ int pci_remove_device(u16 seg, u8 bus, u8 devfn) return -ENODEV; pcidevs_lock(); + spin_lock(&pseg->alldevs_lock); list_for_each_entry ( pdev, &pseg->alldevs_list, alldevs_list ) if ( pdev->bus == bus && pdev->devfn == devfn ) { @@ -907,10 +921,12 @@ int pci_remove_device(u16 seg, u8 bus, u8 devfn) } printk(XENLOG_DEBUG "PCI remove device %pp\n", &pdev->sbdf); free_pdev(pseg, pdev); + list_del(&pdev->alldevs_list); break; } pcidevs_unlock(); + spin_unlock(&pseg->alldevs_lock); return ret; } @@ -1363,6 +1379,7 @@ static int cf_check _dump_pci_devices(struct pci_seg *pseg, void *arg) printk("==== segment %04x ====\n", pseg->nr); + spin_lock(&pseg->alldevs_lock); list_for_each_entry ( pdev, &pseg->alldevs_list, alldevs_list ) { printk("%pp - ", &pdev->sbdf); @@ -1376,6 +1393,7 @@ static int cf_check _dump_pci_devices(struct pci_seg *pseg, void *arg) pdev_dump_msi(pdev); printk("\n"); } + spin_unlock(&pseg->alldevs_lock); return 0; } -- 2.36.1
