Re: [RFC PATCH v2 02/38] KVM: arm/arm64: Enable nested virtualization via command-line

[Jintack Lim]

On Sun, Jul 30, 2017 at 3:59 PM, Christoffer Dall <cdall@xxxxxxxxxx> wrote:
> On Tue, Jul 18, 2017 at 11:58:28AM -0500, Jintack Lim wrote:
>> Add a new kernel parameter(kvm-arm.nested) to enable KVM/ARM nested
>> virtualization support. This kernel parameter on arm architecture is
>> ignored since nested virtualization is not supported on arm.
>>
>> Note that this kernel parameter will not have any impact until nested
>> virtualization support is completed. Just add this parameter first to
>> use it when implementing nested virtualization support.
>>
>> Signed-off-by: Jintack Lim <jintack.lim@xxxxxxxxxx>
>> ---
>>  Documentation/admin-guide/kernel-parameters.txt |  4 ++++
>>  arch/arm/include/asm/kvm_host.h                 |  4 ++++
>>  arch/arm64/include/asm/kvm_host.h               |  2 ++
>>  arch/arm64/kvm/Makefile                         |  2 ++
>>  arch/arm64/kvm/nested.c                         | 26 +++++++++++++++++++++++++
>>  virt/kvm/arm/arm.c                              |  2 ++
>>  6 files changed, 40 insertions(+)
>>  create mode 100644 arch/arm64/kvm/nested.c
>>
>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>> index aa8341e..8fb152d 100644
>> --- a/Documentation/admin-guide/kernel-parameters.txt
>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>> @@ -1841,6 +1841,10 @@
>>                       [KVM,ARM] Trap guest accesses to GICv3 common
>>                       system registers
>>
>> +     kvm-arm.nested=
>> +                     [KVM,ARM] Allow nested virtualization in KVM/ARM.
>> +                     Default is 0 (disabled)
>
> We may want to say "on systems that support it" or something like that
> here as well.
>

Sounds good! Thanks.

>> +
>>       kvm-intel.ept=  [KVM,Intel] Disable extended page tables
>>                       (virtualized MMU) support on capable Intel chips.
>>                       Default is 1 (enabled)
>> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
>> index 127e2dd..00b0f97 100644
>> --- a/arch/arm/include/asm/kvm_host.h
>> +++ b/arch/arm/include/asm/kvm_host.h
>> @@ -299,4 +299,8 @@ int kvm_arm_vcpu_arch_get_attr(struct kvm_vcpu *vcpu,
>>  int kvm_arm_vcpu_arch_has_attr(struct kvm_vcpu *vcpu,
>>                              struct kvm_device_attr *attr);
>>
>> +static inline int __init kvmarm_nested_cfg(char *buf)
>> +{
>> +     return 0;
>> +}
>>  #endif /* __ARM_KVM_HOST_H__ */
>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
>> index 0c4fd1f..dcc4df8 100644
>> --- a/arch/arm64/include/asm/kvm_host.h
>> +++ b/arch/arm64/include/asm/kvm_host.h
>> @@ -386,4 +386,6 @@ static inline void __cpu_init_stage2(void)
>>                 "PARange is %d bits, unsupported configuration!", parange);
>>  }
>>
>> +int __init kvmarm_nested_cfg(char *buf);
>> +
>>  #endif /* __ARM64_KVM_HOST_H__ */
>> diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
>> index 5d98100..f513047 100644
>> --- a/arch/arm64/kvm/Makefile
>> +++ b/arch/arm64/kvm/Makefile
>> @@ -35,3 +35,5 @@ kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/vgic/vgic-debug.o
>>  kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/irqchip.o
>>  kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/arch_timer.o
>>  kvm-$(CONFIG_KVM_ARM_PMU) += $(KVM)/arm/pmu.o
>> +
>> +kvm-$(CONFIG_KVM_ARM_HOST) += nested.o
>> diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
>> new file mode 100644
>> index 0000000..79f38da
>> --- /dev/null
>> +++ b/arch/arm64/kvm/nested.c
>> @@ -0,0 +1,26 @@
>> +/*
>> + * Copyright (C) 2017 - Columbia University and Linaro Ltd.
>> + * Author: Jintack Lim <jintack.lim@xxxxxxxxxx>
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License version 2 as
>> + * published by the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> + * GNU General Public License for more details.
>> + *
>> + * You should have received a copy of the GNU General Public License
>> + * along with this program.  If not, see <http://www.gnu.org/licenses/>.
>> + */
>> +
>> +#include <linux/kvm.h>
>> +#include <linux/kvm_host.h>
>> +
>> +static bool nested_param;
>> +
>> +int __init kvmarm_nested_cfg(char *buf)
>> +{
>> +     return strtobool(buf, &nested_param);
>> +}
>> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
>> index a39a1e1..1c1c772 100644
>> --- a/virt/kvm/arm/arm.c
>> +++ b/virt/kvm/arm/arm.c
>> @@ -67,6 +67,8 @@
>>
>>  static DEFINE_PER_CPU(unsigned char, kvm_arm_hardware_enabled);
>>
>> +early_param("kvm-arm.nested", kvmarm_nested_cfg);
>> +
>>  static void kvm_arm_set_running_vcpu(struct kvm_vcpu *vcpu)
>>  {
>>       BUG_ON(preemptible());
>> --
>> 1.9.1
>>