Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1667249

On an AMD SEV enabled host with an SEV enabled guest, attaching an
assigned device to the VM results in a failure to start the VM:

qemu-kvm: -device vfio-pci,host=01:00.0,id=hostdev0,bus=pci.2,addr=0x0: sev_ram_block_added: failed to register region (0x7fd96e6bb000+0x20000) error 'Cannot allocate memory'

In this example the assigned device is a simple Intel 82574L NIC:

01:00.0 Ethernet controller: Intel Corporation 82574L Gigabit Network Connection
	Subsystem: Intel Corporation Gigabit CT Desktop Adapter
	Flags: bus master, fast devsel, latency 0, IRQ 89, NUMA node 0
	Memory at fb9c0000 (32-bit, non-prefetchable) [size=128K]
	Memory at fb900000 (32-bit, non-prefetchable) [size=512K]

Note that the error indicates the region as (base+size) where a size
of 0x20000 is 128K, which matches that of BAR0 for the device.
dmesg on the host also reports:

SVM: SEV: Failure locking 32 pages.

SEV guests make use of the RAMBlock notifier in QEMU to add page
pinnings for SEV; the kernel side of the call only knows how to pin
pages with get_user_pages(), and this currently faults on non-page
backed mappings (e.g. the mmap of an MMIO BAR).

To resolve this failure, change the order of the memory region type
assignment and avoid pinning device memory regions.

Cc: "Danilo C. L. de Paula" <ddepaula@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-devel@nongnu.org
Cc: Richard Henderson <rth@twiddle.net>

Danilo C. L. de Paula (2):
  redhat: branching qemu-kvm to rhel-8.1.0
  redhat: renaming branch to rhel-8.1.0

Gary R Hook (2):
  Subject: memory: Fix the memory region type assignment order
  Subject: target/i386: sev: Do not pin the ram device memory region

 .gitpublish       |  6 +++---
 memory.c          |  9 ++++++++-
 target/i386/sev.c | 11 +++++++++++
 3 files changed, 22 insertions(+), 4 deletions(-)

-- 
2.18.1

On 10/04/19 02:08, Gary R Hook wrote:
> Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1667249
> 
> On an AMD SEV enabled host with an SEV enabled guest, attaching an
> assigned device to the VM results in a failure to start the VM:
> 
> qemu-kvm: -device vfio-pci,host=01:00.0,id=hostdev0,bus=pci.2,addr=0x0: sev_ram_block_added: failed to register region (0x7fd96e6bb000+0x20000) error 'Cannot allocate memory'
> 
> In this example the assigned device is a simple Intel 82574L NIC:
> 
> 01:00.0 Ethernet controller: Intel Corporation 82574L Gigabit Network Connection
> 	Subsystem: Intel Corporation Gigabit CT Desktop Adapter
> 	Flags: bus master, fast devsel, latency 0, IRQ 89, NUMA node 0
> 	Memory at fb9c0000 (32-bit, non-prefetchable) [size=128K]
> 	Memory at fb900000 (32-bit, non-prefetchable) [size=512K]
> 
> Note that the error indicates the region as (base+size) where a size
> of 0x20000 is 128K, which matches that of BAR0 for the device.
> dmesg on the host also reports:
> 
> SVM: SEV: Failure locking 32 pages.
> 
> SEV guests make use of the RAMBlock notifier in QEMU to add page
> pinnings for SEV; the kernel side of the call only knows how to pin
> pages with get_user_pages(), and this currently faults on non-page
> backed mappings (e.g. the mmap of an MMIO BAR).
> 
> To resolve this failure, change the order of the memory region type
> assignment and avoid pinning device memory regions.
> 
> Cc: "Danilo C. L. de Paula" <ddepaula@redhat.com>
> Cc: Eduardo Habkost <ehabkost@redhat.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: qemu-devel@nongnu.org
> Cc: Richard Henderson <rth@twiddle.net>
> 
> Danilo C. L. de Paula (2):
>   redhat: branching qemu-kvm to rhel-8.1.0
>   redhat: renaming branch to rhel-8.1.0
> 
> Gary R Hook (2):
>   Subject: memory: Fix the memory region type assignment order
>   Subject: target/i386: sev: Do not pin the ram device memory region
> 
>  .gitpublish       |  6 +++---
>  memory.c          |  9 ++++++++-
>  target/i386/sev.c | 11 +++++++++++
>  3 files changed, 22 insertions(+), 4 deletions(-)
> 

Acked-by: Paolo Bonzini <pbonzini@redhat.com>