Messages in this thread | | | Subject | Re: [kvmtool PATCH v9 5/5] KVM: arm/arm64: Add a vcpu feature for pointer authentication | From | Amit Daniel Kachhap <> | Date | Wed, 17 Apr 2019 18:06:11 +0530 |
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Hi,
On 4/16/19 10:02 PM, Dave Martin wrote: > On Fri, Apr 12, 2019 at 08:50:36AM +0530, Amit Daniel Kachhap wrote: >> This patch adds 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. >> >> Command line options --enable-ptrauth and --disable-ptrauth are added >> to use this feature. However, if those options are not provided then >> also this feature is enabled if host supports this capability. >> >> The macros defined in the headers are not in sync and should be replaced >> from the upstream. >> >> Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com> >> --- >> Changes since v8: >> * Added option --enable-ptrauth and --disable-ptrauth to use ptrauth. Also >> enable ptrauth if no option provided and Host supports ptrauth. [Dave Martin] >> * The macro definition are not linear as the kvmtool is not synchronised with the >> kernel changes present in kvmarm/next tree. >> >> arm/aarch32/include/kvm/kvm-cpu-arch.h | 1 + >> arm/aarch64/include/asm/kvm.h | 2 ++ >> arm/aarch64/include/kvm/kvm-config-arch.h | 6 +++++- >> arm/aarch64/include/kvm/kvm-cpu-arch.h | 2 ++ >> arm/include/arm-common/kvm-config-arch.h | 2 ++ >> arm/kvm-cpu.c | 11 +++++++++++ >> include/linux/kvm.h | 2 ++ >> 7 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..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..a2546e6 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 5 /* CPU uses address pointer authentication */ >> +#define KVM_ARM_VCPU_PTRAUTH_GENERIC 6 /* 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..0279b13 100644 >> --- a/arm/aarch64/include/kvm/kvm-config-arch.h >> +++ b/arm/aarch64/include/kvm/kvm-config-arch.h >> @@ -8,7 +8,11 @@ >> "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', "enable-ptrauth", &(cfg)->enable_ptrauth, \ >> + "Enables pointer authentication"), \ >> + OPT_BOOLEAN('\0', "disable-ptrauth", &(cfg)->disable_ptrauth, \ >> + "Disables pointer 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..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..1b4287d 100644 >> --- a/arm/include/arm-common/kvm-config-arch.h >> +++ b/arm/include/arm-common/kvm-config-arch.h >> @@ -10,6 +10,8 @@ struct kvm_config_arch { >> bool aarch32_guest; >> bool has_pmuv3; >> u64 kaslr_seed; >> + bool enable_ptrauth; >> + bool disable_ptrauth; >> enum irqchip_type irqchip; >> u64 fw_addr; >> }; >> diff --git a/arm/kvm-cpu.c b/arm/kvm-cpu.c >> index 7780251..a45a649 100644 >> --- a/arm/kvm-cpu.c >> +++ b/arm/kvm-cpu.c >> @@ -69,6 +69,17 @@ struct kvm_cpu *kvm_cpu__arch_init(struct kvm *kvm, unsigned long cpu_id) >> } >> >> /* >> + * Always enable Pointer Authentication if requested. If system supports >> + * this extension then also enable it by default provided no disable >> + * request present. >> + */ >> + if ((kvm->cfg.arch.enable_ptrauth) || > > Nit: redundant () ok. > >> + (kvm__supports_extension(kvm, KVM_CAP_ARM_PTRAUTH_ADDRESS) && > > Funny indentation? ok will align it. > >> + kvm__supports_extension(kvm, KVM_CAP_ARM_PTRAUTH_GENERIC) && >> + !kvm->cfg.arch.disable_ptrauth)) >> + vcpu_init.features[0] |= ARM_VCPU_PTRAUTH_FEATURE; >> + > > Hmm, we have some weird behaviours here: --enable-ptrauth > --disable-ptrauth will result in us trying to enable it, and May be 1 more check can be added here like,
if (kvm->cfg.arch.enable_ptrauth && kvm->cfg.arch.disable_ptrauth) { print_err("Only 1 option should be supplied\n"); ret -EINVAL; }
> --enable-ptrauth without the required caps will result in an unhelpful > "Unable to initialise vcpu" error message. I'm not sure this is a > whole lot worse than the way other options behave today, though.
Since now ptrauth is enabled by default if system supports it even though it is not explicitly requested. so I thought --enable-ptrauth option has to now forcefully enable ptrauth and may cause some error message in failure. Did I interpret something different from your last suggestion[1]?
Actually we can skip with --enable-ptrauth and have just 2 option, * By default enable ptrauth if system supports it. * --disable-ptrauth: useful to migrate non-ptrauth guests on ptrauth hosts
[1]:https://lkml.org/lkml/2019/4/5/171
Thanks, Amit Daniel > > You could try to be more explicit about what happens in these cases, but > I'm not sure it's worth it given the state of the existing code.
> > [...] > > Cheers > ---Dave >
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