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

[Eric Auger]

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?

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.
> 
>