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Bug 1346920

Summary:	vIOMMU: prevent unsupported configurations with vfio
Product:	Red Hat Enterprise Linux 7	Reporter:	Alex Williamson <alex.williamson>
Component:	qemu-kvm-rhev	Assignee:	Alex Williamson <alex.williamson>
Status:	CLOSED ERRATA	QA Contact:	Pei Zhang <pezhang>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	7.3	CC:	alex.williamson, chayang, huding, jinzhao, juzhang, knoel, pezhang, racedoro, virt-maint, xfu
Target Milestone:	rc
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:	qemu-kvm-rhev-2.6.0-12.el7	Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2016-11-07 21:17:43 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Alex Williamson 2016-06-15 16:11:06 UTC

Description of problem:

vIOMMU support (VT-d emulation) is available in QEMU 2.6, but does not support the necessary notifier calling points to support an external IOMMU cache, such as necessary for vfio-pci.  We don't want users enabling configurations which we know to be broken and currently unsupported.  Prevent them.

Version-Release number of selected component (if applicable):


How reproducible:
100%

Steps to Reproduce:
1. Enable vfio-pci device with -M q35,iommu=on
2.
3.

Actual results:
VM starts, but vfio-pci device does not work


Expected results:
vfio-pci device should either work or the configuration should generate an error.  Here we're trying to enable the latter.

Additional info:
Patches posted upstream: https://lists.nongnu.org/archive/html/qemu-devel/2016-06/msg04253.html

Comment 2 Miroslav Rezanina 2016-07-08 08:39:58 UTC

Fix included in qemu-kvm-rhev-2.6.0-12.el7

Comment 4 Pei Zhang 2016-07-14 07:05:30 UTC

Reproduced:
Versions:
qemu-kvm-rhev-2.6.0-11.el7.x86_64

Steps:
1. Boot guest with iommu=on and vfio-pci device

# lspci | grep Eth
01:00.0 Ethernet controller: Intel Corporation Ethernet Controller 10-Gigabit X540-AT2 (rev 01)
...

# /usr/libexec/qemu-kvm \
-M q35,iommu=on \
-device vfio-pci,host=01:00.0

(qemu) qemu-kvm: -device vfio-pci,host=01:00.0,bus=root.1,id=pf: iommu map to non memory area 0
qemu-kvm: -device vfio-pci,host=01:00.0,bus=root.1,id=pf: iommu map to non memory area 1000
qemu-kvm: -device vfio-pci,host=01:00.0,bus=root.1,id=pf: iommu map to non memory area 2000
...
qemu-kvm: -device vfio-pci,host=01:00.0: iommu map to non memory area f09c000
qemu-kvm: -device vfio-pci,host=01:00.0: iommu map to non memory area f09d000
...


Hi Alex,
In your description, the guest should work. But it doesn't, qemu will keep printing "qemu-kvm: -device vfio-pci,host=01:00.0,bus=root.1,id=pf: iommu map to non memory area xxx",it looks like in a indefinite loop. 

So is this bug reproduced? Thanks.


Verified:
Versions:
qemu-img-rhev-2.6.0-13.el7.x86_64

Steps:
1. Boot guest with iommu=on and vfio-pci device
# /usr/libexec/qemu-kvm \
-M q35,iommu=on \
-device vfio-pci,host=01:00.0

(qemu) qemu: hardware error: Device at bus root.1 addr 00.0 requires iommu notifier which is currently not supported by intel-iommu emulation
CPU #0:
EAX=00000000 EBX=00000000 ECX=00000000 EDX=000206a1
ESI=00000000 EDI=00000000 EBP=00000000 ESP=00000000
EIP=0000fff0 EFL=00000002 [-------] CPL=0 II=0 A20=1 SMM=0 HLT=0
ES =0000 00000000 0000ffff 00009300
CS =f000 ffff0000 0000ffff 00009b00
SS =0000 00000000 0000ffff 00009300
DS =0000 00000000 0000ffff 00009300
FS =0000 00000000 0000ffff 00009300
GS =0000 00000000 0000ffff 00009300
LDT=0000 00000000 0000ffff 00008200
TR =0000 00000000 0000ffff 00008b00
GDT=     00000000 0000ffff
IDT=     00000000 0000ffff
CR0=60000010 CR2=00000000 CR3=00000000 CR4=00000000
DR0=0000000000000000 DR1=0000000000000000 DR2=0000000000000000 DR3=0000000000000000 
DR6=00000000ffff0ff0 DR7=0000000000000400
EFER=0000000000000000
FCW=037f FSW=0000 [ST=0] FTW=00 MXCSR=00001f80
FPR0=0000000000000000 0000 FPR1=0000000000000000 0000
FPR2=0000000000000000 0000 FPR3=0000000000000000 0000
FPR4=0000000000000000 0000 FPR5=0000000000000000 0000
FPR6=0000000000000000 0000 FPR7=0000000000000000 0000
XMM00=00000000000000000000000000000000 XMM01=00000000000000000000000000000000
XMM02=00000000000000000000000000000000 XMM03=00000000000000000000000000000000
XMM04=00000000000000000000000000000000 XMM05=00000000000000000000000000000000
XMM06=00000000000000000000000000000000 XMM07=00000000000000000000000000000000
CPU #1:
EAX=00000000 EBX=00000000 ECX=00000000 EDX=000206a1
ESI=00000000 EDI=00000000 EBP=00000000 ESP=00000000
EIP=0000fff0 EFL=00000002 [-------] CPL=0 II=0 A20=1 SMM=0 HLT=0
ES =0000 00000000 0000ffff 00009300
CS =f000 ffff0000 0000ffff 00009b00
SS =0000 00000000 0000ffff 00009300
DS =0000 00000000 0000ffff 00009300
FS =0000 00000000 0000ffff 00009300
GS =0000 00000000 0000ffff 00009300
LDT=0000 00000000 0000ffff 00008200
TR =0000 00000000 0000ffff 00008b00
GDT=     00000000 0000ffff
IDT=     00000000 0000ffff
CR0=60000010 CR2=00000000 CR3=00000000 CR4=00000000
DR0=0000000000000000 DR1=0000000000000000 DR2=0000000000000000 DR3=0000000000000000 
DR6=00000000ffff0ff0 DR7=0000000000000400
EFER=0000000000000000
FCW=037f FSW=0000 [ST=0] FTW=00 MXCSR=00001f80
FPR0=0000000000000000 0000 FPR1=0000000000000000 0000
FPR2=0000000000000000 0000 FPR3=0000000000000000 0000
FPR4=0000000000000000 0000 FPR5=0000000000000000 0000
FPR6=0000000000000000 0000 FPR7=0000000000000000 0000
XMM00=00000000000000000000000000000000 XMM01=00000000000000000000000000000000
XMM02=00000000000000000000000000000000 XMM03=00000000000000000000000000000000
XMM04=00000000000000000000000000000000 XMM05=00000000000000000000000000000000
XMM06=00000000000000000000000000000000 XMM07=00000000000000000000000000000000
Aborted (core dumped)


Qemu quit with prompting 'hardware error' which seems to be expected. But qemu core dump. So I file a new bug[1] to track this new issue.
[1]Bug 1356445 - qemu core dump when booting with 'iommu=on' and vfio-pci

Comment 5 Alex Williamson 2016-07-14 12:52:39 UTC

This is the expected behavior.

Comment 6 Pei Zhang 2016-08-12 00:50:51 UTC

According to Comment 4 and Comment 5, set this bug to VERIFIED.

Comment 8 errata-xmlrpc 2016-11-07 21:17:43 UTC

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2016-2673.html