| Message ID | 1555994558-26349-4-git-send-email-amit.kachhap@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Add ARMv8.3 pointer authentication for kvm guest | expand |
On Tue, Apr 23, 2019 at 10:12:36AM +0530, Amit Daniel Kachhap wrote: > Now that the building blocks of pointer authentication are present, lets > add userspace flags KVM_ARM_VCPU_PTRAUTH_ADDRESS and > KVM_ARM_VCPU_PTRAUTH_GENERIC. These flags will enable pointer > authentication for the KVM guest on a per-vcpu basis through the ioctl > KVM_ARM_VCPU_INIT. > > This features will allow the KVM guest to allow the handling of > pointer authentication instructions or to treat them as undefined > if not set. > > Necessary documentations are added to reflect the changes done. > > Reviewed-by: Dave Martin <Dave.Martin@arm.com> > Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com> > Cc: Mark Rutland <mark.rutland@arm.com> > Cc: Marc Zyngier <marc.zyngier@arm.com> > Cc: Christoffer Dall <christoffer.dall@arm.com> > Cc: kvmarm@lists.cs.columbia.edu > --- > Changed since v9: > * Fixed tab alignment at few places [Dave Martin]. > * Split the system capability checks [Dave Martin]. > > Documentation/arm64/pointer-authentication.txt | 22 +++++++++++++++++---- > Documentation/virtual/kvm/api.txt | 10 ++++++++++ > arch/arm64/include/asm/kvm_host.h | 2 +- > arch/arm64/include/uapi/asm/kvm.h | 2 ++ > arch/arm64/kvm/reset.c | 27 ++++++++++++++++++++++++++ > 5 files changed, 58 insertions(+), 5 deletions(-) > > diff --git a/Documentation/arm64/pointer-authentication.txt b/Documentation/arm64/pointer-authentication.txt > index 5baca42..fc71b33 100644 > --- a/Documentation/arm64/pointer-authentication.txt > +++ b/Documentation/arm64/pointer-authentication.txt > @@ -87,7 +87,21 @@ used to get and set the keys for a thread. > 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 each virtual cpu is > +initialised by passing flags KVM_ARM_VCPU_PTRAUTH_[ADDRESS/GENERIC] and > +requesting these two separate cpu features to be enabled. The current KVM > +guest implementation works by enabling both features together, so both > +these userspace flags are checked before enabling pointer authentication. > +The separate userspace flag will allow to have no userspace ABI changes > +if support is added in the future to allow these two features to be > +enabled independently of one another. > + > +As Arm Architecture specifies that Pointer Authentication feature is > +implemented along with the VHE feature so KVM arm64 ptrauth code relies > +on VHE mode to be present. > + > +Additionally, when these vcpu feature flags are not set then KVM will > +filter out the Pointer Authentication system key registers from > +KVM_GET/SET_REG_* ioctls and mask those features from cpufeature ID > +register. Any attempt to use the Pointer Authentication instructions will > +result in an UNDEFINED exception being injected into the guest. > diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt > index e410a9f..32afe7f 100644 > --- a/Documentation/virtual/kvm/api.txt > +++ b/Documentation/virtual/kvm/api.txt > @@ -2761,6 +2761,16 @@ Possible features: > - KVM_ARM_VCPU_PMU_V3: Emulate PMUv3 for the CPU. > Depends on KVM_CAP_ARM_PMU_V3. > > + - KVM_ARM_VCPU_PTRAUTH_ADDRESS: Enables Address Pointer authentication > + for arm64 only. > + Both KVM_ARM_VCPU_PTRAUTH_ADDRESS and KVM_ARM_VCPU_PTRAUTH_GENERIC > + must be requested or neither must be requested. > + > + - KVM_ARM_VCPU_PTRAUTH_GENERIC: Enables Generic Pointer authentication > + for arm64 only. > + Both KVM_ARM_VCPU_PTRAUTH_ADDRESS and KVM_ARM_VCPU_PTRAUTH_GENERIC > + must be requested or neither must be requested. > + This looks pretty clear now. > - KVM_ARM_VCPU_SVE: Enables SVE for the CPU (arm64 only). > Depends on KVM_CAP_ARM_SVE. > Requires KVM_ARM_VCPU_FINALIZE(KVM_ARM_VCPU_SVE): > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h > index 7eebea7..f772ac2 100644 > --- a/arch/arm64/include/asm/kvm_host.h > +++ b/arch/arm64/include/asm/kvm_host.h > @@ -49,7 +49,7 @@ > > #define KVM_MAX_VCPUS VGIC_V3_MAX_CPUS > > -#define KVM_VCPU_MAX_FEATURES 5 > +#define KVM_VCPU_MAX_FEATURES 7 > > #define KVM_REQ_SLEEP \ > KVM_ARCH_REQ_FLAGS(0, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP) > diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h > index edd2db8..7b7ac0f 100644 > --- a/arch/arm64/include/uapi/asm/kvm.h > +++ b/arch/arm64/include/uapi/asm/kvm.h > @@ -104,6 +104,8 @@ 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 */ > #define KVM_ARM_VCPU_SVE 4 /* enable SVE for this CPU */ > +#define KVM_ARM_VCPU_PTRAUTH_ADDRESS 5 /* VCPU uses address authentication */ > +#define KVM_ARM_VCPU_PTRAUTH_GENERIC 6 /* VCPU uses generic authentication */ > > struct kvm_vcpu_init { > __u32 target; > diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c > index 3402543..028d0c6 100644 > --- a/arch/arm64/kvm/reset.c > +++ b/arch/arm64/kvm/reset.c > @@ -221,6 +221,27 @@ static void kvm_vcpu_reset_sve(struct kvm_vcpu *vcpu) > memset(vcpu->arch.sve_state, 0, vcpu_sve_state_size(vcpu)); > } > > +static int kvm_vcpu_enable_ptrauth(struct kvm_vcpu *vcpu) > +{ > + /* Support ptrauth only if the system supports these capabilities. */ > + if (!has_vhe()) > + return -EINVAL; > + > + if (!system_supports_address_auth() || > + !system_supports_generic_auth()) > + return -EINVAL; Since pointer auth implies v8.3 and v8.3 implies v8.1 and v8.1 implies VHE: ((system_supports_address_auth() || system_supports_generic_auth()) && !has_vhe()) implies that the hardware is broken or the kernel is buggy. So, it probably makes sense to write if (!system_supports_address_auth() || !system_supports_generic_auth()) return -EINVAL; if (WARN_ON(!has_vhe())) return -EINVAL; This is not essential, and doesn't affect the ABI -- so we could apply it on top later on. [...] FWIW: Reviewed-by: Dave Martin <Dave.Martin@arm.com> (for the updates) Cheers ---Dave
Hi, On 4/23/19 9:15 PM, Dave Martin wrote: > On Tue, Apr 23, 2019 at 10:12:36AM +0530, Amit Daniel Kachhap wrote: >> Now that the building blocks of pointer authentication are present, lets >> add userspace flags KVM_ARM_VCPU_PTRAUTH_ADDRESS and >> KVM_ARM_VCPU_PTRAUTH_GENERIC. These flags will enable pointer >> authentication for the KVM guest on a per-vcpu basis through the ioctl >> KVM_ARM_VCPU_INIT. >> >> This features will allow the KVM guest to allow the handling of >> pointer authentication instructions or to treat them as undefined >> if not set. >> >> Necessary documentations are added to reflect the changes done. >> >> Reviewed-by: Dave Martin <Dave.Martin@arm.com> >> Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com> >> Cc: Mark Rutland <mark.rutland@arm.com> >> Cc: Marc Zyngier <marc.zyngier@arm.com> >> Cc: Christoffer Dall <christoffer.dall@arm.com> >> Cc: kvmarm@lists.cs.columbia.edu >> --- >> Changed since v9: >> * Fixed tab alignment at few places [Dave Martin]. >> * Split the system capability checks [Dave Martin]. >> >> Documentation/arm64/pointer-authentication.txt | 22 +++++++++++++++++---- >> Documentation/virtual/kvm/api.txt | 10 ++++++++++ >> arch/arm64/include/asm/kvm_host.h | 2 +- >> arch/arm64/include/uapi/asm/kvm.h | 2 ++ >> arch/arm64/kvm/reset.c | 27 ++++++++++++++++++++++++++ >> 5 files changed, 58 insertions(+), 5 deletions(-) >> >> diff --git a/Documentation/arm64/pointer-authentication.txt b/Documentation/arm64/pointer-authentication.txt >> index 5baca42..fc71b33 100644 >> --- a/Documentation/arm64/pointer-authentication.txt >> +++ b/Documentation/arm64/pointer-authentication.txt >> @@ -87,7 +87,21 @@ used to get and set the keys for a thread. >> 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 each virtual cpu is >> +initialised by passing flags KVM_ARM_VCPU_PTRAUTH_[ADDRESS/GENERIC] and >> +requesting these two separate cpu features to be enabled. The current KVM >> +guest implementation works by enabling both features together, so both >> +these userspace flags are checked before enabling pointer authentication. >> +The separate userspace flag will allow to have no userspace ABI changes >> +if support is added in the future to allow these two features to be >> +enabled independently of one another. >> + >> +As Arm Architecture specifies that Pointer Authentication feature is >> +implemented along with the VHE feature so KVM arm64 ptrauth code relies >> +on VHE mode to be present. >> + >> +Additionally, when these vcpu feature flags are not set then KVM will >> +filter out the Pointer Authentication system key registers from >> +KVM_GET/SET_REG_* ioctls and mask those features from cpufeature ID >> +register. Any attempt to use the Pointer Authentication instructions will >> +result in an UNDEFINED exception being injected into the guest. >> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt >> index e410a9f..32afe7f 100644 >> --- a/Documentation/virtual/kvm/api.txt >> +++ b/Documentation/virtual/kvm/api.txt >> @@ -2761,6 +2761,16 @@ Possible features: >> - KVM_ARM_VCPU_PMU_V3: Emulate PMUv3 for the CPU. >> Depends on KVM_CAP_ARM_PMU_V3. >> >> + - KVM_ARM_VCPU_PTRAUTH_ADDRESS: Enables Address Pointer authentication >> + for arm64 only. >> + Both KVM_ARM_VCPU_PTRAUTH_ADDRESS and KVM_ARM_VCPU_PTRAUTH_GENERIC >> + must be requested or neither must be requested. >> + >> + - KVM_ARM_VCPU_PTRAUTH_GENERIC: Enables Generic Pointer authentication >> + for arm64 only. >> + Both KVM_ARM_VCPU_PTRAUTH_ADDRESS and KVM_ARM_VCPU_PTRAUTH_GENERIC >> + must be requested or neither must be requested. >> + > > This looks pretty clear now. > >> - KVM_ARM_VCPU_SVE: Enables SVE for the CPU (arm64 only). >> Depends on KVM_CAP_ARM_SVE. >> Requires KVM_ARM_VCPU_FINALIZE(KVM_ARM_VCPU_SVE): >> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h >> index 7eebea7..f772ac2 100644 >> --- a/arch/arm64/include/asm/kvm_host.h >> +++ b/arch/arm64/include/asm/kvm_host.h >> @@ -49,7 +49,7 @@ >> >> #define KVM_MAX_VCPUS VGIC_V3_MAX_CPUS >> >> -#define KVM_VCPU_MAX_FEATURES 5 >> +#define KVM_VCPU_MAX_FEATURES 7 >> >> #define KVM_REQ_SLEEP \ >> KVM_ARCH_REQ_FLAGS(0, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP) >> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h >> index edd2db8..7b7ac0f 100644 >> --- a/arch/arm64/include/uapi/asm/kvm.h >> +++ b/arch/arm64/include/uapi/asm/kvm.h >> @@ -104,6 +104,8 @@ 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 */ >> #define KVM_ARM_VCPU_SVE 4 /* enable SVE for this CPU */ >> +#define KVM_ARM_VCPU_PTRAUTH_ADDRESS 5 /* VCPU uses address authentication */ >> +#define KVM_ARM_VCPU_PTRAUTH_GENERIC 6 /* VCPU uses generic authentication */ >> >> struct kvm_vcpu_init { >> __u32 target; >> diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c >> index 3402543..028d0c6 100644 >> --- a/arch/arm64/kvm/reset.c >> +++ b/arch/arm64/kvm/reset.c >> @@ -221,6 +221,27 @@ static void kvm_vcpu_reset_sve(struct kvm_vcpu *vcpu) >> memset(vcpu->arch.sve_state, 0, vcpu_sve_state_size(vcpu)); >> } >> >> +static int kvm_vcpu_enable_ptrauth(struct kvm_vcpu *vcpu) >> +{ >> + /* Support ptrauth only if the system supports these capabilities. */ >> + if (!has_vhe()) >> + return -EINVAL; >> + >> + if (!system_supports_address_auth() || >> + !system_supports_generic_auth()) >> + return -EINVAL; > > Since pointer auth implies v8.3 and v8.3 implies v8.1 and v8.1 implies VHE: > > ((system_supports_address_auth() || system_supports_generic_auth()) && > !has_vhe()) implies that the hardware is broken or the kernel is buggy. > > So, it probably makes sense to write > > if (!system_supports_address_auth() || > !system_supports_generic_auth()) > return -EINVAL; > > if (WARN_ON(!has_vhe())) > return -EINVAL; Yes agree with you. Now with config VHE restriction set it makes more sense that this situation will only occur now in buggy h/w case. > > This is not essential, and doesn't affect the ABI -- so we could apply > it on top later on. > > [...] > > FWIW: > > Reviewed-by: Dave Martin <Dave.Martin@arm.com> (for the updates) Thanks for the review effort. Thanks, Amit D > > Cheers > ---Dave >
diff --git a/Documentation/arm64/pointer-authentication.txt b/Documentation/arm64/pointer-authentication.txt index 5baca42..fc71b33 100644 --- a/Documentation/arm64/pointer-authentication.txt +++ b/Documentation/arm64/pointer-authentication.txt @@ -87,7 +87,21 @@ used to get and set the keys for a thread. 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 each virtual cpu is +initialised by passing flags KVM_ARM_VCPU_PTRAUTH_[ADDRESS/GENERIC] and +requesting these two separate cpu features to be enabled. The current KVM +guest implementation works by enabling both features together, so both +these userspace flags are checked before enabling pointer authentication. +The separate userspace flag will allow to have no userspace ABI changes +if support is added in the future to allow these two features to be +enabled independently of one another. + +As Arm Architecture specifies that Pointer Authentication feature is +implemented along with the VHE feature so KVM arm64 ptrauth code relies +on VHE mode to be present. + +Additionally, when these vcpu feature flags are not set then KVM will +filter out the Pointer Authentication system key registers from +KVM_GET/SET_REG_* ioctls and mask those features from cpufeature ID +register. Any attempt to use the Pointer Authentication instructions will +result in an UNDEFINED exception being injected into the guest. diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt index e410a9f..32afe7f 100644 --- a/Documentation/virtual/kvm/api.txt +++ b/Documentation/virtual/kvm/api.txt @@ -2761,6 +2761,16 @@ Possible features: - KVM_ARM_VCPU_PMU_V3: Emulate PMUv3 for the CPU. Depends on KVM_CAP_ARM_PMU_V3. + - KVM_ARM_VCPU_PTRAUTH_ADDRESS: Enables Address Pointer authentication + for arm64 only. + Both KVM_ARM_VCPU_PTRAUTH_ADDRESS and KVM_ARM_VCPU_PTRAUTH_GENERIC + must be requested or neither must be requested. + + - KVM_ARM_VCPU_PTRAUTH_GENERIC: Enables Generic Pointer authentication + for arm64 only. + Both KVM_ARM_VCPU_PTRAUTH_ADDRESS and KVM_ARM_VCPU_PTRAUTH_GENERIC + must be requested or neither must be requested. + - KVM_ARM_VCPU_SVE: Enables SVE for the CPU (arm64 only). Depends on KVM_CAP_ARM_SVE. Requires KVM_ARM_VCPU_FINALIZE(KVM_ARM_VCPU_SVE): diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index 7eebea7..f772ac2 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -49,7 +49,7 @@ #define KVM_MAX_VCPUS VGIC_V3_MAX_CPUS -#define KVM_VCPU_MAX_FEATURES 5 +#define KVM_VCPU_MAX_FEATURES 7 #define KVM_REQ_SLEEP \ KVM_ARCH_REQ_FLAGS(0, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP) diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h index edd2db8..7b7ac0f 100644 --- a/arch/arm64/include/uapi/asm/kvm.h +++ b/arch/arm64/include/uapi/asm/kvm.h @@ -104,6 +104,8 @@ 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 */ #define KVM_ARM_VCPU_SVE 4 /* enable SVE for this CPU */ +#define KVM_ARM_VCPU_PTRAUTH_ADDRESS 5 /* VCPU uses address authentication */ +#define KVM_ARM_VCPU_PTRAUTH_GENERIC 6 /* VCPU uses generic authentication */ struct kvm_vcpu_init { __u32 target; diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c index 3402543..028d0c6 100644 --- a/arch/arm64/kvm/reset.c +++ b/arch/arm64/kvm/reset.c @@ -221,6 +221,27 @@ static void kvm_vcpu_reset_sve(struct kvm_vcpu *vcpu) memset(vcpu->arch.sve_state, 0, vcpu_sve_state_size(vcpu)); } +static int kvm_vcpu_enable_ptrauth(struct kvm_vcpu *vcpu) +{ + /* Support ptrauth only if the system supports these capabilities. */ + if (!has_vhe()) + return -EINVAL; + + if (!system_supports_address_auth() || + !system_supports_generic_auth()) + return -EINVAL; + /* + * For now make sure that both address/generic pointer authentication + * features are requested by the userspace together. + */ + if (!test_bit(KVM_ARM_VCPU_PTRAUTH_ADDRESS, vcpu->arch.features) || + !test_bit(KVM_ARM_VCPU_PTRAUTH_GENERIC, vcpu->arch.features)) + return -EINVAL; + + vcpu->arch.flags |= KVM_ARM64_GUEST_HAS_PTRAUTH; + return 0; +} + /** * kvm_reset_vcpu - sets core registers and sys_regs to reset value * @vcpu: The VCPU pointer @@ -261,6 +282,12 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu) kvm_vcpu_reset_sve(vcpu); } + if (test_bit(KVM_ARM_VCPU_PTRAUTH_ADDRESS, vcpu->arch.features) || + test_bit(KVM_ARM_VCPU_PTRAUTH_GENERIC, vcpu->arch.features)) { + if (kvm_vcpu_enable_ptrauth(vcpu)) + goto out; + } + switch (vcpu->arch.target) { default: if (test_bit(KVM_ARM_VCPU_EL1_32BIT, vcpu->arch.features)) {