[PATCH v10 00/59] KVM: arm64: ARMv8.3/8.4 Nested Virtualization support

[Eric Auger]

Hi Miguel,

On 6/10/23 10:25, Miguel Luis wrote:
> Hi Eric,
> 
>> On 7 Jun 2023, at 16:40, Eric Auger <eauger at redhat.com> wrote:
>>
>> Hi Miguel,
>>
>> On 6/6/23 19:52, Miguel Luis wrote:
>>> Hello Eric, Marc,
>>>
>>>> On 6 Jun 2023, at 09:33, Eric Auger <eauger at redhat.com> wrote:
>>>>
>>>> Hi Marc,
>>>>
>>>> On 5/17/23 16:12, Marc Zyngier wrote:
>>>>> On Wed, 17 May 2023 09:59:45 +0100,
>>>>> Eric Auger <eauger at redhat.com> wrote:
>>>>>>
>>>>>> Hi Marc,
>>>>>> Hi Marc,
>>>>>> On 5/16/23 22:28, Marc Zyngier wrote:
>>>>>>> On Tue, 16 May 2023 17:53:14 +0100,
>>>>>>> Eric Auger <eauger at redhat.com> wrote:
>>>>>>>>
>>>>>>>> Hi Marc,
>>>>>>>>
>>>>>>>> On 5/15/23 19:30, Marc Zyngier wrote:
>>>>>>>>> This is the 4th drop of NV support on arm64 for this year.
>>>>>>>>>
>>>>>>>>> For the previous episodes, see [1].
>>>>>>>>>
>>>>>>>>> What's changed:
>>>>>>>>>
>>>>>>>>> - New framework to track system register traps that are reinjected in
>>>>>>>>> guest EL2. It is expected to replace the discrete handling we have
>>>>>>>>> enjoyed so far, which didn't scale at all. This has already fixed a
>>>>>>>>> number of bugs that were hidden (a bunch of traps were never
>>>>>>>>> forwarded...). Still a work in progress, but this is going in the
>>>>>>>>> right direction.
>>>>>>>>>
>>>>>>>>> - Allow the L1 hypervisor to have a S2 that has an input larger than
>>>>>>>>> the L0 IPA space. This fixes a number of subtle issues, depending on
>>>>>>>>> how the initial guest was created.
>>>>>>>>>
>>>>>>>>> - Consequently, the patch series has gone longer again. Boo. But
>>>>>>>>> hopefully some of it is easier to review...
>>>>>>>>>
>>>>>>>>> [1] https://lore.kernel.org/r/20230405154008.3552854-1-maz@kernel.org
>>>>>>>>
>>>>>>>> I have started testing this and when booting my fedora guest I get
>>>>>>>>
>>>>>>>> [  151.796544] kvm [7617]: Unsupported guest sys_reg access at:
>>>>>>>> 23f425fd0 [80000209]
>>>>>>>> [  151.796544]  { Op0( 3), Op1( 3), CRn(14), CRm( 3), Op2( 1), func_write },
>>>>>>>>
>>>>>>>> as soon as the host has kvm-arm.mode=nested
>>>>>>>>
>>>>>>>> This seems to be triggered very early by EDK2
>>>>>>>> (ArmPkg/Drivers/TimerDxe/TimerDxe.c).
>>>>>>>>
>>>>>>>> If I am not wrong this CNTV_CTL_EL0. Do you have any idea?
>>>>>>>
>>>>>>> So here's my current analysis:
>>>>>>>
>>>>>>> I assume you are running EDK2 as the L1 guest in a nested
>>>>>>> configuration. I also assume that you are not running on an Apple
>>>>>>> CPU. If these assumptions are correct, then EDK2 runs at vEL2, and is
>>>>>>> in nVHE mode.
>>>>>>>
>>>>>>> Finally, I'm going to assume that your implementation has FEAT_ECV and
>>>>>>> FEAT_NV2, because I can't see how it could fail otherwise.
>>>>>> all the above is correct.
>>>>>>>
>>>>>>> In these precise conditions, KVM sets the CNTHCTL_EL2.EL1TVT bit so
>>>>>>> that we can trap the EL0 virtual timer and faithfully emulate it (it
>>>>>>> is otherwise written to memory, which isn't very helpful).
>>>>>>
>>>>>> indeed
>>>>>>>
>>>>>>> As it turns out, we don't handle these traps. I didn't spot it because
>>>>>>> my test machines are all Apple boxes that don't have a nVHE mode, so
>>>>>>> nothing on the nVHE path is getting *ANY* coverage. Hint: having
>>>>>>> access to such a machine would help (shipping address on request!).
>>>>>>> Otherwise, I'll eventually kill the nVHE support altogether.
>>>>>>>
>>>>>>> I have written the following patch, which compiles, but that I cannot
>>>>>>> test with my current setup. Could you please give it a go?
>>>>>>
>>>>>> with the patch below, my guest boots nicely. You did it great on the 1st
>>>>>> shot!!! So this fixes my issue. I will continue testing the v10.
>>>>>
>>>>> Thanks a lot for reporting the issue and testing my hacks. I'll
>>>>> eventually fold it into the rest of the series.
>>>>>
>>>>> By the way, what are you using as your VMM? I'd really like to
>>>>> reproduce your setup.
>>>> Sorry I missed your reply. I am using libvirt + qemu (feat Miguel's RFC)
>>>> and fedora L1 guest.
>>>>
>>>
>>> Following this subject, I’ve forward ported Alexandru’s KUT patches
>>> ( and I encourage others to do it also =) ) which expose an EL2 test that
>>
>> Do you have a branch available with Alexandru's rebased kut series?
> 
> Now I do :)
> 
> https://github.com/mluis/kvm-unit-tests/tree/nv-WIP

Cool, thanks!

Eric
> 
> Thanks,
> Miguel
> 
>>
>> Thanks
>>
>> Eric
>>> does three checks:
>>>
>>> - whether VHE is supported and enabled
>>> - disable VHE
>>> - re-enable VHE  
>>>
>>> I’m running qemu with virtualization=on as well to run this test and it is passing although
>>> problems seem to happen when running with virtualization=off, which I’m still looking into it.
>>>
>>> Thanks
>>> Miguel
>>>
>>>> Thanks to your fix, this boots fine. But at the moment it does not
>>>> reboot and hangs in edk2 I think. Unfortunately this time I have no
>>>> trace on host :-( While looking at your series I will add some traces.
>>>>
>>>> Eric
>>>>>
>>>>> Cheers,
>>>>>
>>>>> M.
> 
>