Re: [RFC v2 0/5] ARM Nested Virt Support

[Eric Auger]

Hi Peter,

On 3/5/24 17:57, Peter Maydell wrote:
> On Fri, 9 Feb 2024 at 16:00, Eric Auger <eric.auger@redhat.com> wrote:
>> This series adds ARM Nested Virtualization support in KVM mode.
>> This is a respin of previous contributions from Miguel [1] and Haibo [2].
>>
>> This was tested with Marc's v11 [3] on Ampere HW with fedora L1 guest and
>> L2 guests booted without EDK2. However it does not work yet with
>> EDK2 but it looks unrelated to this qemu integration (host hard lockups).
>>
>> The host needs to be booted with "kvm-arm.mode=nested" option and
>> qemu needs to be invoked with :
>>
>> -machine virt,virtualization=on
>>
>> There is a known issue with hosts supporting SVE. Kernel does not support 
>> both
>> SVE and NV2 and the current qemu integration has an issue with the
>> scratch_host_vcpu startup because both are enabled if exposed by the kernel.
>> This is independent on whether sve is disabled on the command line. 
>> Unfortunately
>> I lost access to the HW that expose that issue so I couldn't fix it in this
>> version.
>>
>> This series can be found at:
>> https://github.com/eauger/qemu/tree/v8.2-nv-rfcv2
>>
>> Previous version from Miguel:
>> [1] 
>> https://lore.kernel.org/all/20230227163718.62003-1-miguel.luis@oracle.com/
>> Previous version from Haibo:
>> [2] 
>> https://lore.kernel.org/qemu-devel/cover.1617281290.git.haibo.xu@linaro.org/
>> [3] Marc's kernel v11 series:
>>     [PATCH v11 00/43] KVM: arm64: Nested Virtualization support (FEAT_NV2 
>> only)
>>     
>> https://lore.kernel.org/linux-arm-kernel/20231120131027.854038-1-maz@kernel.org/T/
>>     available at: https://github.com/eauger/linux/tree/nv-6.8-nv2-v11
>>
>> Haibo Xu (5):
>>   [Placeholder] headers: Partial headers update for NV2 enablement
>>   hw/arm: Allow setting KVM vGIC maintenance IRQ
>>   target/arm/kvm: Add helper to detect EL2 when using KVM
>>   target/arm: Enable feature ARM_FEATURE_EL2 if EL2 is supported
>>   hw/arm/virt: Allow virt extensions with KVM
>>
>>  hw/arm/virt.c                      |  6 +++++-
>>  hw/intc/arm_gicv3_common.c         |  1 +
>>  hw/intc/arm_gicv3_kvm.c            | 21 +++++++++++++++++++++
>>  include/hw/intc/arm_gicv3_common.h |  1 +
>>  linux-headers/asm-arm64/kvm.h      |  1 +
>>  linux-headers/linux/kvm.h          |  1 +
>>  target/arm/kvm.c                   | 21 +++++++++++++++++++++
>>  target/arm/kvm_arm.h               | 12 ++++++++++++
>>  8 files changed, 63 insertions(+), 1 deletion(-)
> All the patches in this series seem reasonable, but the series
> as a whole is so short I wonder if we're missing something :-)
> Does migration Just Work? (I guess as long as the kernel exposes
> all the EL2 sysregs via the ONE_REG ioctl interface it ought to...)
To be honest I have not tested yet. I would also guess there is no mig
blocker but that definitively deserves some testing. I will check before
sending the next version.
>
> Anyway, I don't think there's anything that stood out as needing
> major changes, so for now I guess we just wait for whenever the
> KVM side patches eventually land.

yup

Thanks

Eric
>
> thanks
> -- PMM
>