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

From	Dan Streetman <ddstreet@ieee.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH] xen: do not re-use pirq number cached in pci device msi msg data
Date	2017-02-21 16:40 +0100
Message-ID	<tdkHM-4r9-21@gated-at.bofh.it> (permalink)
References	<sZgkF-5dS-7@gated-at.bofh.it> <sZgkF-5dS-5@gated-at.bofh.it> <sZiFP-6v3-21@gated-at.bofh.it>
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On Fri, Jan 13, 2017 at 5:30 PM, Konrad Rzeszutek Wilk
<konrad.wilk@oracle.com> 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:
>> https://lists.xen.org/archives/html/xen-devel/2017-01/msg00447.html
>>
>> Fixes: af42b8d12f8a ("xen: fix MSI setup and teardown for PV on HVM guests")
>> Signed-off-by: Dan Streetman <dan.streetman@canonical.com>
>
> Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

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...

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Re: [PATCH] xen: do not re-use pirq number cached in pci device msi  msg data Dan Streetman <ddstreet@ieee.org> - 2017-02-21 16:40 +0100
  Re: [PATCH] xen: do not re-use pirq number cached in pci device msi  msg data Juergen Gross <jgross@suse.com> - 2017-02-21 16:50 +0100
    Re: [PATCH] xen: do not re-use pirq number cached in pci device msi  msg data Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-02-21 17:00 +0100
      Re: [PATCH] xen: do not re-use pirq number cached in pci device msi  msg data Bjorn Helgaas <helgaas@kernel.org> - 2017-02-22 15:30 +0100
        Re: [PATCH] xen: do not re-use pirq number cached in pci device msi  msg data Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-02-22 16:20 +0100

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