| Message ID | 1523049683-11782-1-git-send-email-igor.druzhinin@citrix.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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On Fri, Apr 06, 2018 at 10:21:23PM +0100, Igor Druzhinin wrote: > Commit 99605175c (xen-pt: Fix PCI devices re-attach failed) introduced > a subtle bug. As soon as the guest switches off Bus Mastering on the > device it immediately causes all the BARs be unmapped due to the DMA > address space of the device being changed. This is undesired behavior > because the guest may try to communicate with the device after that > which triggers the following errors in the logs: > > [00:05.0] xen_pt_bar_read: Error: Should not read BAR through QEMU. @0x0000000000000200 > [00:05.0] xen_pt_bar_write: Error: Should not write BAR through QEMU. @0x0000000000000200 > > The issue that the original patch tried to workaround (uneven number of > region_add/del calls on device attach/detach) was fixed in later QEMU > versions. Do you know when the issue was fixed?
On 17/04/18 15:15, Anthony PERARD wrote: > On Fri, Apr 06, 2018 at 10:21:23PM +0100, Igor Druzhinin wrote: >> Commit 99605175c (xen-pt: Fix PCI devices re-attach failed) introduced >> a subtle bug. As soon as the guest switches off Bus Mastering on the >> device it immediately causes all the BARs be unmapped due to the DMA >> address space of the device being changed. This is undesired behavior >> because the guest may try to communicate with the device after that >> which triggers the following errors in the logs: >> >> [00:05.0] xen_pt_bar_read: Error: Should not read BAR through QEMU. @0x0000000000000200 >> [00:05.0] xen_pt_bar_write: Error: Should not write BAR through QEMU. @0x0000000000000200 >> >> The issue that the original patch tried to workaround (uneven number of >> region_add/del calls on device attach/detach) was fixed in later QEMU >> versions. > > Do you know when the issue was fixed? > I haven't tracked down a particular version but the previous behavior of memory_listener_unregister() was to remove the listener from the list without calling the callback. It has changed since then and now the callback is called in listener_del_address_space(). Igor
On 17/04/18 15:15, Anthony PERARD wrote: > On Fri, Apr 06, 2018 at 10:21:23PM +0100, Igor Druzhinin wrote: >> Commit 99605175c (xen-pt: Fix PCI devices re-attach failed) introduced >> a subtle bug. As soon as the guest switches off Bus Mastering on the >> device it immediately causes all the BARs be unmapped due to the DMA >> address space of the device being changed. This is undesired behavior >> because the guest may try to communicate with the device after that >> which triggers the following errors in the logs: >> >> [00:05.0] xen_pt_bar_read: Error: Should not read BAR through QEMU. @0x0000000000000200 >> [00:05.0] xen_pt_bar_write: Error: Should not write BAR through QEMU. @0x0000000000000200 >> >> The issue that the original patch tried to workaround (uneven number of >> region_add/del calls on device attach/detach) was fixed in later QEMU >> versions. > > Do you know when the issue was fixed? > I think it's this commit: commit d25836cafd7508090d211e97acfc0abc5ae88daa Author: Peter Xu <peterx@redhat.com> Date: Mon Jan 22 14:02:44 2018 +0800 memory: do explicit cleanup when remove listeners Igor
diff --git a/hw/xen/xen_pt.c b/hw/xen/xen_pt.c index 9b7a960..e5a6eff 100644 --- a/hw/xen/xen_pt.c +++ b/hw/xen/xen_pt.c @@ -907,7 +907,7 @@ out: } } - memory_listener_register(&s->memory_listener, &s->dev.bus_master_as); + memory_listener_register(&s->memory_listener, &address_space_memory); memory_listener_register(&s->io_listener, &address_space_io); s->listener_set = true; XEN_PT_LOG(d,
Commit 99605175c (xen-pt: Fix PCI devices re-attach failed) introduced a subtle bug. As soon as the guest switches off Bus Mastering on the device it immediately causes all the BARs be unmapped due to the DMA address space of the device being changed. This is undesired behavior because the guest may try to communicate with the device after that which triggers the following errors in the logs: [00:05.0] xen_pt_bar_read: Error: Should not read BAR through QEMU. @0x0000000000000200 [00:05.0] xen_pt_bar_write: Error: Should not write BAR through QEMU. @0x0000000000000200 The issue that the original patch tried to workaround (uneven number of region_add/del calls on device attach/detach) was fixed in later QEMU versions. Signed-off-by: Igor Druzhinin <igor.druzhinin@citrix.com> Reported-by: Ross Lagerwall <ross.lagerwall@citrix.com> --- hw/xen/xen_pt.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)