Re: [PATCH] xen: do not re-use pirq number cached in pci device msi msg data

From: Dan Streetman
Date: Tue Feb 21 2017 - 10:32:48 EST

On Fri, Jan 13, 2017 at 5:30 PM, Konrad Rzeszutek Wilk
<konrad.wilk@xxxxxxxxxx> wrote:
> On Fri, Jan 13, 2017 at 03:07:51PM -0500, Dan Streetman wrote:
>> Revert the main part of commit:
>> af42b8d12f8a ("xen: fix MSI setup and teardown for PV on HVM guests")
>> That commit introduced reading the pci device's msi message data to see
>> if a pirq was previously configured for the device's msi/msix, and re-use
>> that pirq. At the time, that was the correct behavior. However, a
>> later change to Qemu caused it to call into the Xen hypervisor to unmap
>> all pirqs for a pci device, when the pci device disables its MSI/MSIX
>> vectors; specifically the Qemu commit:
>> c976437c7dba9c7444fb41df45468968aaa326ad
>> ("qemu-xen: free all the pirqs for msi/msix when driver unload")
>> Once Qemu added this pirq unmapping, it was no longer correct for the
>> kernel to re-use the pirq number cached in the pci device msi message
>> data. All Qemu releases since 2.1.0 contain the patch that unmaps the
>> pirqs when the pci device disables its MSI/MSIX vectors.
>> This bug is causing failures to initialize multiple NVMe controllers
>> under Xen, because the NVMe driver sets up a single MSIX vector for
>> each controller (concurrently), and then after using that to talk to
>> the controller for some configuration data, it disables the single MSIX
>> vector and re-configures all the MSIX vectors it needs. So the MSIX
>> setup code tries to re-use the cached pirq from the first vector
>> for each controller, but the hypervisor has already given away that
>> pirq to another controller, and its initialization fails.
>> This is discussed in more detail at:
>> Fixes: af42b8d12f8a ("xen: fix MSI setup and teardown for PV on HVM guests")
>> Signed-off-by: Dan Streetman <dan.streetman@xxxxxxxxxxxxx>
> Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

This doesn't seem to be applied yet, is it still waiting on another
ack? Or maybe I'm looking at the wrong git tree...