Re: [Qemu-devel] [PATCH v3] ARM: KVM: Enable in-kernel timers with user space gic

[Andrew Jones]

On Tue, Jun 27, 2017 at 05:35:37PM +0200, Alexander Graf wrote:
> When running with KVM enabled, you can choose between emulating the
> gic in kernel or user space. If the kernel supports in-kernel virtualization
> of the interrupt controller, it will default to that. If not, if will
> default to user space emulation.
> 
> Unfortunately when running in user mode gic emulation, we miss out on
> interrupt events which are only available from kernel space, such as the 
> timer.
> This patch leverages the new kernel/user space pending line synchronization 
> for
> timer events. It does not handle PMU events yet.
> 
> Signed-off-by: Alexander Graf <address@hidden>
> Reviewed-by: Andrew Jones <address@hidden>
> 
> ---
> 
> v1 -> v2:
> 
>   - whitespace fixes
>   - use !! to determine whether bit is set
>   - call in-kernel device IRQs out by their name everywhere
> 
> v2 -> v3:
> 
>   - fix last occurence of calling out timer IRQs explicitly
> ---
>  accel/kvm/kvm-all.c    |  5 +++++
>  accel/stubs/kvm-stub.c |  5 +++++
>  hw/intc/arm_gic.c      |  7 +++++++
>  include/sysemu/kvm.h   | 11 +++++++++++
>  target/arm/cpu.h       |  3 +++
>  target/arm/kvm.c       | 51 
> ++++++++++++++++++++++++++++++++++++++++++++++++++
>  6 files changed, 82 insertions(+)
>

Tried testing this on a gicv3 machine, a ThunderX2. The guest kernel
complains with

 GICv3: GIC: unable to set SRE (disabled at EL2), panic ahead

but no panic occurs. Instead it hangs in cpu_do_idle(), waiting forever
for an interrupt.

AAVMF also complains about SRE support, actually it asserts it.

 ASSERT [ArmGicDxe] 
/builddir/build/BUILD/ovmf-c325e41585e3/ArmVirtPkg/Library/ArmVirtGicArchLib/ArmVirtGicArchLib.c(113):
 IccSre & (1 << 0)


I still haven't seen any problems with gicv2 though.

Thanks,
drew