Re: [PATCH v4 0/4] KVM: arm64: BUG FIX: Correctly handle zero register transfers

[Andrew Jones <drjones@redhat.com>]

On Mon, Dec 07, 2015 at 12:48:12PM +0300, Pavel Fedin wrote:
>  Hello!
> 
> > FYI, I tried writing test cases for this issue with kvm-unit-tests. The
> > issue didn't reproduce for me. It's quite possible my test cases are
> > flawed
> 
>  Indeed they are, a very little thing fell through again... :)
>  It's not just SP, it's SP_EL0. And you never initialize it to anything because your code always runs in kernel mode, so it's just
> zero, so you get your zero.
>  But if you add a little thing in the beginning of your main():
> 
> asm volatile("msr sp_el0, %0" : : "r" (0xDEADC0DE0BADC0DE));

Ah! Thanks for this. The mmio test does now fail for me too. The sysreg
test still doesn't fail for me (even though I'm doing the above on the
vcpu I use for that too). Maybe there's something weird with which reg
I'm using, and whether or not my attempt to get trapping enabled on it
is working the way I expected. I'll play with it some more.

> 
>  then you have it:
> --- cut ---
> [root@thunderx-2 kvm-unit-tests]# ./arm-run arm/xzr-test.flat -smp 2
> qemu-system-aarch64 -machine virt,accel=kvm:tcg,gic-version=host -cpu host -device virtio-serial-device -device
> virtconsole,chardev=ctd -chardev testdev,id=ctd -display none -serial stdio -kernel arm/xzr-test.flat -smp 2
> PASS: mmio: sanity check: read 0x55555555
> FAIL: mmio: 'str wzr' check: read 0x0badc0de
> vm_setup_vq: virtqueue 0 already setup! base=0xa003e00
> chr_testdev_init: chr-testdev: can't init virtqueues
> --- cut ---
> 
>  Here i run only MMIO test, because i could not compile sysreg one, so i simply commented it out.
> 
>  P.S. Could you also apply something like the following to arm/run:
> --- cut ---
> arm/run | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/arm/run b/arm/run
> index 662a856..3890c8c 100755
> --- a/arm/run
> +++ b/arm/run
> @@ -33,7 +33,11 @@ if $qemu $M -chardev testdev,id=id -initrd . 2>&1 \
>  	exit 2
>  fi
>  
> -M='-machine virt,accel=kvm:tcg'
> +if $qemu $M,? 2>&1 | grep gic-version > /dev/null; then
> +	GIC='gic-version=host,'
> +fi
> +
> +M="-machine virt,${GIC}accel=kvm:tcg"
>  chr_testdev='-device virtio-serial-device'
>  chr_testdev+=' -device virtconsole,chardev=ctd -chardev testdev,id=ctd'
> --- cut ---

Yes, I'll send a patch for this soon. I actually have something similar to this
in my local tree already, I just hadn't bothered sending it as I didn't think
anybody else needed it yet.

> 
>  Without it qemu does not work on GICv3-only hardware, like my board, because it defaults to gic-version=2. I don't post the patch
> on the mailing lists, because in order to be able to post this 5-liner i'll need to go through the formal approval procedure at my
> company, and i just don't want to bother for a single small fix. :) Will do as a "Reported-by:".

It'd be nice if you could go through the procedure. You've been sending
patches to KVM, and ideally we'll start trying to send kvm-unit-tests
patches along with feature patches.

Thanks,
drew