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From: Matthew Rosato <mjrosato@linux.ibm.com>
To: alex.williamson@redhat.com, pmorel@linux.ibm.com, schnelle@linux.ibm.com
Cc: david@redhat.com, cohuck@redhat.com, qemu-devel@nongnu.org,
	pasic@linux.ibm.com, borntraeger@de.ibm.com,
	qemu-s390x@nongnu.org, rth@twiddle.net
Subject: [RFC PATCH] s390x/pci: vfio-pci breakage with disabled mem enforcement
Date: Thu, 23 Jul 2020 11:13:55 -0400	[thread overview]
Message-ID: <1595517236-17823-1-git-send-email-mjrosato@linux.ibm.com> (raw)

I noticed that after kernel commit abafbc55 'vfio-pci: Invalidate mmaps
and block MMIO access on disabled memory' vfio-pci via qemu on s390x
fails spectacularly, with errors in qemu like:

qemu-system-s390x: vfio_region_read(0001:00:00.0:region0+0x0, 4) failed: Input/output error

From read to bar 0 originating out of hw/s390x/s390-pci-inst.c:zpci_read_bar().

So, I'm trying to figure out how to get vfio-pci happy again on s390x.  From
a bit of tracing, we seem to be triggering the new trap in
__vfio_pci_memory_enabled().  Sure enough, if I just force this function to
return 'true' as a test case, things work again.
The included patch attempts to enforce the setting, which restores everything
to working order but also triggers vfio_bar_restore() in the process....  So
this isn't the right answer, more of a proof-of-concept.

@Alex: Any guidance on what needs to happen to make qemu-s390x happy with this
recent kernel change?

@Nilkas/@Pierre: I wonder if this might be related to host device is_virtfn?
I note that my host device lspci output looks like:

0000:00:00.0 Ethernet controller: Mellanox Technologies MT27710 Family [ConnectX-4 Lx Virtual Function]

But the device is not marked as is_virtfn..  Otherwise, Alex's fix
from htps://lkml.org/lkml/2020/6/25/628 should cover the case.



Matthew Rosato (1):
  s390x/pci: Enforce PCI_COMMAND_MEMORY for vfio-pci

 hw/s390x/s390-pci-inst.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

-- 
1.8.3.1



             reply	other threads:[~2020-07-23 15:15 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-23 15:13 Matthew Rosato [this message]
2020-07-23 15:13 ` [RFC PATCH] s390x/pci: Enforce PCI_COMMAND_MEMORY for vfio-pci Matthew Rosato
2020-07-23 16:29 ` [RFC PATCH] s390x/pci: vfio-pci breakage with disabled mem enforcement Alex Williamson
2020-07-23 18:12   ` Matthew Rosato
2020-07-27 15:40   ` Pierre Morel
2020-07-27 16:37     ` Matthew Rosato
2020-07-27 16:47     ` Alex Williamson
2020-07-28  9:33       ` Niklas Schnelle
2020-07-28 12:52         ` Alex Williamson
2020-07-28 14:13           ` Niklas Schnelle
2020-07-28  8:59     ` Niklas Schnelle
2020-07-24  9:46 ` Niklas Schnelle
2020-07-24  9:53   ` Niklas Schnelle
2020-07-24 14:15   ` Niklas Schnelle

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