Messages in this thread | | | Subject | Re: [PATCH v6 4/6] arm64/kvm: add a userspace option to enable pointer authentication | From | Amit Daniel Kachhap <> | Date | Mon, 4 Mar 2019 16:26:34 +0530 |
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Hi James,
On 2/27/19 12:03 AM, James Morse wrote: > 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. ok. > > >> 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. ok. > > >> 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? yes sure. > > >> 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) Yes with including some of Dave SVE patches this wont be required.
Thanks, Amit D > > > Looks good, > > Thanks, > > James >
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