Re: [kvmtool PATCH v5 6/6] arm/kvm: arm64: Add a vcpu feature for pointer authentication

Julien Thierry
2019-01-28T14:56:18Z

Hi Amit,

On 28/01/2019 06:58, Amit Daniel Kachhap wrote:
> This is a runtime feature and can be enabled by --ptrauth option.
>
> Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Christoffer Dall <christoffer.dall@arm.com>
> Cc: Marc Zyngier <marc.zyngier@arm.com>
> Cc: Kristina Martsenko <kristina.martsenko@arm.com>
> Cc: kvmarm@lists.cs.columbia.edu
> Cc: Ramana Radhakrishnan <ramana.radhakrishnan@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> ---
> arm/aarch32/include/kvm/kvm-cpu-arch.h | 2 ++
> arm/aarch64/include/asm/kvm.h | 3 +++
> arm/aarch64/include/kvm/kvm-arch.h | 1 +
> arm/aarch64/include/kvm/kvm-config-arch.h | 4 +++-
> arm/aarch64/include/kvm/kvm-cpu-arch.h | 2 ++
> arm/aarch64/kvm-cpu.c | 5 +++++
> arm/include/arm-common/kvm-config-arch.h | 1 +
> arm/kvm-cpu.c | 7 +++++++
> include/linux/kvm.h | 1 +
> 9 files changed, 25 insertions(+), 1 deletion(-)
>
> diff --git a/arm/aarch32/include/kvm/kvm-cpu-arch.h b/arm/aarch32/include/kvm/kvm-cpu-arch.h
> index d28ea67..5779767 100644
> --- a/arm/aarch32/include/kvm/kvm-cpu-arch.h
> +++ b/arm/aarch32/include/kvm/kvm-cpu-arch.h
> @@ -13,4 +13,6 @@
> #define ARM_CPU_ID 0, 0, 0
> #define ARM_CPU_ID_MPIDR 5
>
> +unsigned int kvm__cpu_ptrauth_get_feature(void) {}
> +

You probably want a return statement for this function.

> #endif /* KVM__KVM_CPU_ARCH_H */
> diff --git a/arm/aarch64/include/asm/kvm.h b/arm/aarch64/include/asm/kvm.h
> index c286035..0fd183d 100644
> --- a/arm/aarch64/include/asm/kvm.h
> +++ b/arm/aarch64/include/asm/kvm.h
> @@ -98,6 +98,9 @@ struct kvm_regs {
> #define KVM_ARM_VCPU_PSCI_0_2 2 /* CPU uses PSCI v0.2 */
> #define KVM_ARM_VCPU_PMU_V3 3 /* Support guest PMUv3 */
>
> +/* CPU uses address authentication and A key */
> +#define KVM_ARM_VCPU_PTRAUTH 4
> +
> struct kvm_vcpu_init {
> __u32 target;
> __u32 features[7];
> diff --git a/arm/aarch64/include/kvm/kvm-arch.h b/arm/aarch64/include/kvm/kvm-arch.h
> index 9de623a..bd566cb 100644
> --- a/arm/aarch64/include/kvm/kvm-arch.h
> +++ b/arm/aarch64/include/kvm/kvm-arch.h
> @@ -11,4 +11,5 @@
>
> #include "arm-common/kvm-arch.h"
>
> +
> #endif /* KVM__KVM_ARCH_H */
> diff --git a/arm/aarch64/include/kvm/kvm-config-arch.h b/arm/aarch64/include/kvm/kvm-config-arch.h
> index 04be43d..2074684 100644
> --- a/arm/aarch64/include/kvm/kvm-config-arch.h
> +++ b/arm/aarch64/include/kvm/kvm-config-arch.h
> @@ -8,7 +8,9 @@
> "Create PMUv3 device"), \
> OPT_U64('\0', "kaslr-seed", &(cfg)->kaslr_seed, \
> "Specify random seed for Kernel Address Space " \
> - "Layout Randomization (KASLR)"),
> + "Layout Randomization (KASLR)"), \
> + OPT_BOOLEAN('\0', "ptrauth", &(cfg)->has_ptrauth, \
> + "Enable address authentication"),
>
> #include "arm-common/kvm-config-arch.h"
>
> diff --git a/arm/aarch64/include/kvm/kvm-cpu-arch.h b/arm/aarch64/include/kvm/kvm-cpu-arch.h
> index a9d8563..f7b64b7 100644
> --- a/arm/aarch64/include/kvm/kvm-cpu-arch.h
> +++ b/arm/aarch64/include/kvm/kvm-cpu-arch.h
> @@ -17,4 +17,6 @@
> #define ARM_CPU_CTRL 3, 0, 1, 0
> #define ARM_CPU_CTRL_SCTLR_EL1 0
>
> +unsigned int kvm__cpu_ptrauth_get_feature(void);
> +> #endif /* KVM__KVM_CPU_ARCH_H */
> diff --git a/arm/aarch64/kvm-cpu.c b/arm/aarch64/kvm-cpu.c
> index 1b29374..10da2cb 100644
> --- a/arm/aarch64/kvm-cpu.c
> +++ b/arm/aarch64/kvm-cpu.c
> @@ -123,6 +123,11 @@ void kvm_cpu__reset_vcpu(struct kvm_cpu *vcpu)
> return reset_vcpu_aarch64(vcpu);
> }
>
> +unsigned int kvm__cpu_ptrauth_get_feature(void)
> +{
> + return (1UL << KVM_ARM_VCPU_PTRAUTH);
> +}
> +

Couldn't this be a simple:
#define PTRAUTH_FEATURE (1UL << KVM_ARM_VCPU_PTRAUTH)

And just define it to 0 for the aarch32 side?

Cheers,

--
Julien Thierry