[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v2 0/4] Fix device listener interface for PCI to PCI bridges
On Tue, Jun 09, 2015 at 09:18:49AM +0000, Paul Durrant wrote: > > -----Original Message----- > > From: Michael S. Tsirkin [mailto:mst@xxxxxxxxxx] > > Sent: 09 June 2015 10:13 > > To: Don Slutz > > Cc: qemu-devel@xxxxxxxxxx; xen-devel@xxxxxxxxxxxxx; Paul Durrant; > > Stefano Stabellini > > Subject: Re: [PATCH v2 0/4] Fix device listener interface for PCI to PCI > > bridges > > > > On Mon, Jun 08, 2015 at 05:18:48PM -0400, Don Slutz wrote: > > > changes v1 to v2: > > > Split v1 patch into 3. > > > > > > Added a BUG FIX patch (#1: "exec: Do not use MemoryRegion after > > > free"). > > > > > > Technically this bug fix should be a separate patch, however this > > > issue only seems to reproduce when this patch set is applied. > > > > > > > > > Michael S. Tsirkin: > > > "You need some other API that makes sense, probably PCI specific." > > > This is basically patch #2: "Extend device listener interface..." > > > > > > "This is relying on undocumented assumptions and how specific > > > firmware works. There's nothing special about bus number 255, > > > and 0 is not very special either (except it happens to be the > > > reset value)." > > > Dropped all checking of 0 and 255. > > > > > > > > > Open question by Michael S. Tsirkin: > > > > > > >>>> On Thu, May 28, 2015 at 07:25:50AM -0400, Don Slutz wrote: > > > ... > > > >>>> It is not clear to me that the complexity of tracking bus > > > >>>> visibility make sense. Clearly you do. > > > >>> Well what was the point of the change? > > > > > > > > To get config cycles that are valid that you do not get today. > > > > > > > >>> If you don't care that we get irrelevant config cycles why not > > > >>> just send them all to QEMU? > > > >>> > > > > > > > > That would need to be answered by Paul Durrant and/or other people > > (see > > > > below) > > > > > > > > > > We could broadcast config space ioreqs to all emulators, the problem > > > is how do we know (in the case of a read) which emulator is actually > > > the one supplying the data? At some level Xen needs to know who is > > > implementing what. > > > > > > Paul Durrant > > > > Can irrelevant emulators all respond with some kind of nack? > > Xen would pick the one that did respond correctly. > > > > I guess that's possible if we add an extra bit to the ioreq_t, but QEMU would > still need to know when to nack and when to ack. It's simple: ack if we find a device handling the specific BDF. The result would at least be contained. OTOH detecting master aborts in core is useful since it would let us implement error reporting correctly. > It's still much simpler if qemu updates Xen with exact set of (S)BDFs it's > handling. > > Paul I suspect this calls for a bigger change, you need to re-scan all of the tree to detect visible devices. Maybe just write some xen-specific code to do this on each config access. > > > So this patch set just adjusts Xen to correctly know the current set > > > of PCI devices and their bus, device, and function. > > > > > > It does not attempt to calculate the visibility of the PCI devices. > > > > So non-visible devices will appear with invalid bus number values, > > conflicting with the visible devices. > > Seems wrong. > > > > > > > > > > v1: > > > > > > Note: Right now hvmloader in Xen does not handle PCI to PCI bridges > > > and so SeaBIOS does not have access to PCI device(s) on secondary > > > buses. How ever domU can setup the secondary bus(es) and this patch > > > will restore access to these PCI devices. > > > > > > > > > Don Slutz (4): > > > exec: Do not use MemoryRegion after free > > > Extend device listener interface for PCI to PCI bridges > > > xen: Add usage of device listener interface for PCI to PCI bridges > > > xen: Fix map/unmap of pcidev to ioreq server > > > > > > exec.c | 8 ++++-- > > > hw/core/qdev.c | 7 ++++++ > > > hw/pci/pci_bridge.c | 18 +++++++++++++ > > > include/hw/qdev-core.h | 3 +++ > > > include/hw/xen/xen_common.h | 61 > > ++++++++++++++++++++++++++++++++++----------- > > > trace-events | 6 +++-- > > > xen-hvm.c | 20 +++++++++++++-- > > > 7 files changed, 102 insertions(+), 21 deletions(-) > > > > > > -- > > > 1.8.4 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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