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Date: Fri, 5 Apr 2019 12:04:23 +0100
From: Dave Martin <Dave.Martin@....com>
To: Amit Daniel Kachhap <amit.kachhap@....com>
Cc: linux-arm-kernel@...ts.infradead.org,
Marc Zyngier <marc.zyngier@....com>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
Kristina Martsenko <kristina.martsenko@....com>,
kvmarm@...ts.cs.columbia.edu,
Ramana Radhakrishnan <ramana.radhakrishnan@....com>,
linux-kernel@...r.kernel.org
Subject: Re: [kvmtool PATCH v8 9/9] KVM: arm/arm64: Add a vcpu feature for
pointer authentication
On Tue, Apr 02, 2019 at 07:57:17AM +0530, Amit Daniel Kachhap wrote:
> This is a runtime capabality for KVM tool to enable Arm64 8.3 Pointer
> Authentication in guest kernel. Two vcpu features
> KVM_ARM_VCPU_PTRAUTH_[ADDRESS/GENERIC] are supplied together to enable
> Pointer Authentication in KVM guest after checking the capability.
>
> A command line option --ptrauth is also required to select this feature.
>
> Signed-off-by: Amit Daniel Kachhap <amit.kachhap@....com>
> ---
>
> Changes since v7:
> * Added check for capability KVM_CAP_ARM_PTRAUTH_GENERIC
>
> arm/aarch32/include/kvm/kvm-cpu-arch.h | 1 +
> arm/aarch64/include/asm/kvm.h | 2 ++
> arm/aarch64/include/kvm/kvm-config-arch.h | 4 +++-
> arm/aarch64/include/kvm/kvm-cpu-arch.h | 2 ++
> arm/include/arm-common/kvm-config-arch.h | 1 +
> arm/kvm-cpu.c | 7 +++++++
> include/linux/kvm.h | 2 ++
> 7 files changed, 18 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..520ea76 100644
> --- a/arm/aarch32/include/kvm/kvm-cpu-arch.h
> +++ b/arm/aarch32/include/kvm/kvm-cpu-arch.h
> @@ -13,4 +13,5 @@
> #define ARM_CPU_ID 0, 0, 0
> #define ARM_CPU_ID_MPIDR 5
>
> +#define ARM_VCPU_PTRAUTH_FEATURE 0
> #endif /* KVM__KVM_CPU_ARCH_H */
> diff --git a/arm/aarch64/include/asm/kvm.h b/arm/aarch64/include/asm/kvm.h
> index 97c3478..d4d0d8c 100644
> --- a/arm/aarch64/include/asm/kvm.h
> +++ b/arm/aarch64/include/asm/kvm.h
> @@ -102,6 +102,8 @@ struct kvm_regs {
> #define KVM_ARM_VCPU_EL1_32BIT 1 /* CPU running a 32bit VM */
> #define KVM_ARM_VCPU_PSCI_0_2 2 /* CPU uses PSCI v0.2 */
> #define KVM_ARM_VCPU_PMU_V3 3 /* Support guest PMUv3 */
> +#define KVM_ARM_VCPU_PTRAUTH_ADDRESS 4 /* CPU uses address pointer authentication */
> +#define KVM_ARM_VCPU_PTRAUTH_GENERIC 5 /* CPU uses generic pointer authentication */
>
> struct kvm_vcpu_init {
> __u32 target;
> 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"),
This should probably say "pointer", not "address" now, since we enable
both kinds of ptrauth together. (Sorry!)
When discussing how to control SVE, I was eventually convinced that it
is more user-friendly to make SVE default to on if present, and maybe
provide two options --disable-sve, --enable-sve, in case the user wants
to force it off or on instead of just getting what the host supports.
Passing --enable-sve on a host that doesn't support SVE would then lead
to kvmtool bailing out with an error, which is probably better then
silently turning it off.
I don't have this change in my kvmtool patches yet.
What's your view? It makes sense to do things the same way for all
features if we can.
> #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..fcc2107 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
>
> +#define ARM_VCPU_PTRAUTH_FEATURE ((1UL << KVM_ARM_VCPU_PTRAUTH_ADDRESS) \
> + | (1UL << KVM_ARM_VCPU_PTRAUTH_GENERIC))
> #endif /* KVM__KVM_CPU_ARCH_H */
> diff --git a/arm/include/arm-common/kvm-config-arch.h b/arm/include/arm-common/kvm-config-arch.h
> index 5734c46..5badcbd 100644
> --- a/arm/include/arm-common/kvm-config-arch.h
> +++ b/arm/include/arm-common/kvm-config-arch.h
> @@ -10,6 +10,7 @@ struct kvm_config_arch {
> bool aarch32_guest;
> bool has_pmuv3;
> u64 kaslr_seed;
> + bool has_ptrauth;
> enum irqchip_type irqchip;
> u64 fw_addr;
> };
> diff --git a/arm/kvm-cpu.c b/arm/kvm-cpu.c
> index 7780251..398c9d6 100644
> --- a/arm/kvm-cpu.c
> +++ b/arm/kvm-cpu.c
> @@ -68,6 +68,13 @@ struct kvm_cpu *kvm_cpu__arch_init(struct kvm *kvm, unsigned long cpu_id)
> vcpu_init.features[0] |= (1UL << KVM_ARM_VCPU_PSCI_0_2);
> }
>
> + /* Set KVM_ARM_VCPU_PTRAUTH_[ADDRESS/GENERIC] if available */
> + if (kvm__supports_extension(kvm, KVM_CAP_ARM_PTRAUTH_ADDRESS) &&
> + kvm__supports_extension(kvm, KVM_CAP_ARM_PTRAUTH_GENERIC)) {
> + if (kvm->cfg.arch.has_ptrauth)
> + vcpu_init.features[0] |= ARM_VCPU_PTRAUTH_FEATURE;
> + }
> +
> /*
> * If the preferred target ioctl is successful then
> * use preferred target else try each and every target type
> diff --git a/include/linux/kvm.h b/include/linux/kvm.h
> index 6d4ea4b..500ac2b 100644
> --- a/include/linux/kvm.h
> +++ b/include/linux/kvm.h
> @@ -988,6 +988,8 @@ struct kvm_ppc_resize_hpt {
> #define KVM_CAP_ARM_VM_IPA_SIZE 165
> #define KVM_CAP_MANUAL_DIRTY_LOG_PROTECT 166
> #define KVM_CAP_HYPERV_CPUID 167
> +#define KVM_CAP_ARM_PTRAUTH_ADDRESS 168
> +#define KVM_CAP_ARM_PTRAUTH_GENERIC 169
(Note, 168 will probably be KVM_CAP_ARM_SVE, now that the SVE patches
are in kvmarm/next.)
Cheers
---Dave
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