Messages in this thread | | | Subject | Re: [PATCH v6 4/6] arm64/kvm: add a userspace option to enable pointer authentication | From | James Morse <> | Date | Tue, 26 Feb 2019 18:33:15 +0000 |
| |
Hi Amit,
On 19/02/2019 09:24, Amit Daniel Kachhap wrote: > This feature will allow the KVM guest to allow the handling of > pointer authentication instructions or to treat them as undefined > if not set. It uses the existing vcpu API KVM_ARM_VCPU_INIT to > supply this parameter instead of creating a new API. > > A new register is not created to pass this parameter via > SET/GET_ONE_REG interface as just a flag (KVM_ARM_VCPU_PTRAUTH) > supplied is enough to enable this feature.
and an attempt to restore the id register with the other version would fail.
> diff --git a/Documentation/arm64/pointer-authentication.txt b/Documentation/arm64/pointer-authentication.txt > index a25cd21..0529a7d 100644 > --- a/Documentation/arm64/pointer-authentication.txt > +++ b/Documentation/arm64/pointer-authentication.txt > @@ -82,7 +82,8 @@ pointers). > Virtualization > -------------- > > -Pointer authentication is not currently supported in KVM guests. KVM > -will mask the feature bits from ID_AA64ISAR1_EL1, and attempted use of > -the feature will result in an UNDEFINED exception being injected into > -the guest.
> +Pointer authentication is enabled in KVM guest when virtual machine is > +created by passing a flag (KVM_ARM_VCPU_PTRAUTH)
(This is still mixing VM and VCPU)
> + requesting this feature to be enabled.
.. on each vcpu?
> +Without this flag, pointer authentication is not enabled > +in KVM guests and attempted use of the feature will result in an UNDEFINED > +exception being injected into the guest.
'guests' here suggests its a VM property. If you set it on some VCPU but not others KVM will generate undefs instead of enabling the feature. (which is the right thing to do)
I think it needs to be clear this is a per-vcpu property.
> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h > index 97c3478..5f82ca1 100644 > --- a/arch/arm64/include/uapi/asm/kvm.h > +++ b/arch/arm64/include/uapi/asm/kvm.h > @@ -102,6 +102,7 @@ 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 4 /* VCPU uses address authentication */
Just address authentication? I agree with Mark we should have two bits to match what gets exposed to EL0. One would then be address, the other generic.
> diff --git a/arch/arm64/kvm/hyp/ptrauth-sr.c b/arch/arm64/kvm/hyp/ptrauth-sr.c > index 528ee6e..6846a23 100644 > --- a/arch/arm64/kvm/hyp/ptrauth-sr.c > +++ b/arch/arm64/kvm/hyp/ptrauth-sr.c > @@ -93,9 +93,23 @@ void kvm_arm_vcpu_ptrauth_reset(struct kvm_vcpu *vcpu)
> +/** > + * kvm_arm_vcpu_ptrauth_allowed - checks if ptrauth feature is allowed by user > + * > + * @vcpu: The VCPU pointer > + * > + * This function will be used to check userspace option to have ptrauth or not > + * in the guest kernel. > + */ > +bool kvm_arm_vcpu_ptrauth_allowed(const struct kvm_vcpu *vcpu) > +{ > + return kvm_supports_ptrauth() && > + test_bit(KVM_ARM_VCPU_PTRAUTH, vcpu->arch.features); > +}
This isn't used from world-switch, could it be moved to guest.c?
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c > index 12529df..f7bcc60 100644 > --- a/arch/arm64/kvm/sys_regs.c > +++ b/arch/arm64/kvm/sys_regs.c > @@ -1055,7 +1055,7 @@ static bool access_cntp_cval(struct kvm_vcpu *vcpu, > } > > /* Read a sanitised cpufeature ID register by sys_reg_desc */ > -static u64 read_id_reg(struct sys_reg_desc const *r, bool raz) > +static u64 read_id_reg(struct kvm_vcpu *vcpu, struct sys_reg_desc const *r, bool raz)
(It might be easier on the reviewer to move these mechanical changes to an earlier patch)
Looks good,
Thanks,
James
| |